Dissertations / Theses on the topic 'Grapes Diseases and pests Australia'

Bibliography: leaves 148-166. This study identifies genetic variation in Australian Uncinula necator populations. Techniques were developed for molecular and phenotypic markers for U. necator. Mating types of Australian clonal lines were identified and viable cleistothecia and infective ascospores were produced in vitro. The study establishes the foundation for investigating the population biology of U. necator, by identifying two distinct genetic groups, A and B, and micro-geographical variation among 35 clonal lines from various Australian viticultural regions.

Downy mildew, caused by the biotrophic Oomycete Plasmopara viticola, is one of the most important diseases of grapevines world wide. It is particularly destructive in temperate viticultural regions that experience warm wet conditions during the vegetative growth of the vine (Wong et al., 2001). The disease is not normally a problem in mediterranean climates where the growing season tends to be hot and dry (Mullins et al., 1992; Sivasithamparam, 1993). Grape downy mildew is however a major disease in Australian viticulture (McLean et al., 1984; Magarey et al., 1991). Grape downy mildew was first reported in Europe in 1878 (Viennot-Bourgin, 1981). In Australia, it was recorded for the first time in 1917 at Rutherglen in Victoria (Vic) (de Castella, 1917). The first recorded outbreak of the disease in Western Australia (WA) occurred in 1997 in a small planting of vines in the far north of the state. In the subsequent year, it was detected in widespread commercial viticulture in the Swan Valley production area, near Perth (McKirdy et al., 1999). The pathogen has since been found in all grape growing regions of WA. Since its introduction into European vineyards in the 1880?s, P. viticola has become one of the world?s most investigated grapevine pathogens. Many aspects its basic biology however remain unknown (Wong et al., 2001). Due to the recent detection of P. viticola in WA, little is known of the nature of strains of the pathogen in the state and their response to local environmental conditions. Much of the research concerning the influence of environmental factors on the development of P. viticola has been conducted in Europe e.g. parts of France and Germany. Due to significant differences in climatic conditions and a shorter selection time on the pathogen in WA, much of the information described in European studies may not be directly applicable to the grape downy mildew disease situation in WA. The focus of this thesis was to examine epidemiological aspects of P. viticola in the mediterranean climate of WA. The environmental conditions that could favour the development of epidemics by strains of the pathogen that have been detected in the state were determined. The existence of P. viticola ecotypes and genetic variation among strains from WA and the Eastern states of Australia was also investigated.

Bibliography: leaves 81-100. Entry of inoculum into a crop and disease development in the crop cannot be prevented because spores are airborne and there is a lack of highly resistant varieties. This makes complete control of chocolate spot unlikely. It should however, be possible to improve current levels of disease control through the integration of the factors identified in the study.

Thesis (MScAgric.)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: Phomopsis cane and leaf spot disease of grapevine is an economically important disease in many of the vine-growing areas of the world. Four different Phomopsis spp. have previously been associated with this disease. The present study investigates the taxonomic significance of the different taxa found on grapevines in South Africa, as well as the endophytic growth and fungicide sensitivity of Phomopsis viticola isolates. The thesis is compiled of several different parts, which deal with specific, but related topics, and hence some duplication has been unavoidable. Understanding the epidemiology of a disease is important for the correct timing of disease control. To investigate the endophytic growth of P. viticola, asymptomatic shoots were collected at eight different growth stages. Nodes, internodes, leaf petioles, leaves, tendrils and bunch peduncles were investigated. Two Phomopsis spp., taxon 1 and 2 were identified in this study. The Phomopsis viticola-complex had a relative importance of 9% and accounted for 3% of the isolations. P. viticola (taxon 2) is mainly isolated from the nodes and internodes. Inoculations of healthy, young vine tissue confirmed taxon 2 to be a virulent pathogen, suggesting that it is a latent pathogen rather than an endophyte. In contrast, taxon 1 appeared to be a true endophyte, and did not seem to be an important pathogen on vines. The true identity of the causal organism of Phomopsis cane and leaf spot disease was investigated by collecting samples from 58 different vineyards in the grapevine growing areas of the Western Cape. P. viiicola occurred in grapevine material collected from Lutzville to Swellendam, but was not found in the Oudtshoorn and Orange River grapevine areas. Diaporthe perjuncta (taxon 1), P. vutcola (taxon 2), taxon 3 and a Phomopsis species commonly associated with shoot blight of peaches in the U.S.A., P. amygdali, were identified among the South African grapevine isolates. Examination of the Australian culture designated as taxon 4 found it to be a species of Libertella, thus excluding it from the P. viticola-complex. An Italian isolate was found to represent a species of Phomopsis not previously known from grapevines, and this was subsequently described as taxon 5. Species delimitation was based on morphological and cultural characteristics, stem inoculations and the formation of the teleomorph in vitro. The identity of each morphological taxon was confirmed by means of phylogenetic analyses of the nuclear ribosomal DNA internal transcribed spacers (ITS 1 and ITS2) and the 5' end partial sequence of the mitochondrial small subunit (mtSSU). P. amygdali, associated with peach shoot blight in the U.S.A., was isolated once only and appeared to be of lesser importance in this disease complex. Furthermore, taxa 1 (Diaporthe perjuncta) and 3 were also rarely encountered and proved to be non-pathogenic, indicating their non-functional role in Phomopsis cane and leaf spot disease. Taxon 2 (Phomopsis viticolas was common and widely distributed in diseased vineyards. This taxon was associated with the typical disease symptoms and proved to be pathogenic. Morphologically taxon 2 corresponded best with P. viticola, which was also neotypified in this study. Taxon 2 was mostly isolated from buds and nodes, indicating that these are important sites in which the fungus survives during winter. Molecular data indicated that taxon 3 and P. amygdali were not host specific to grapevine. The currently used foliar fungicides were compared to the new strobilurin fungicides. The effects of nine fungicides (azoxystrobin, flusilazole, folpet, fosetyl- Al+mancozeb, kresoxim-methyl, mancozeb, penconazole, spiroxamine and trifloxystrobin) were tested in vitro on inhibition of mycelial growth. The following EC50 (ug/ml) values were obtained: azoxystrobin (0.350), flusilazole (0.007), folpet (4.489), fosetyl-Al+mancozeb (3.925), kresoxim-methyl (1.665), mancozeb (2.891), penconazole (0.023), spiroxamine (0.321) and trifloxystrobin (0.051). Additionally, azoxystrobin, folpet, kresoxim-methyl, mancozeb, propineb and trifloxystrobin were tested for their ability to inhibit spore germination in vitro. The subsequent EC50 (ug/ml) values were obtained: azoxystrobin 0.123), folpet (0.510), kresoxim-methyl (0.0037), mancozeb (0.250), propineb (0.156) and trifloxystrobin (0.003). The results reported in part 4 showed that the strobilurin fungicides inhibited the mycelial growth and spore germination of P. viticola. However, further trials need to be conducted to verify these findings under field conditions. In the present study taxa 1, 3 and P. amygdali were infrequently isolated, suggesting that they played a less prominent role in the P. viticolacomplex.
AFRIKAANSE OPSOMMING: Streepvleksiekte van wingerd is 'n ekonomies belangrike siekte wat in die meeste wingerdproduserende gebiede van die wêreld voorkom. Vier Phomopsis spesies is in die verlede met dié siekte geassosieer. Hierdie studie ondersoek die taksonomiese belangrikheid van die verskillende taksa wat op wingerd in Suid Afrika gevind word, asook die endofietiese groei en fungisiedsensitiwiteit van die Phomopsis vitico/a isolate. Hierdie tesis bestaan uit verskeie dele met spesifieke, maar verwante onderwerpe wat tot onafwendbare duplisering lei. Dit is belangrik om die epidemiologie van 'n siekte te verstaan sodat korrekte en tydsberekende siektebeheer toegepas kan word. Die endofietiese groei van P. vitico/a is ondersoek deur simptoomlose lote by agt verskillende groei stadiums te versamel. Nodusse, internodusse, blaarstele, blare, rankies en trosstele is ondersoek. Twee Phomopsis spp., takson 1 en 2 is geïdentifiseer. Die Phomopsis vitico/a-kompleks het 3% van die isolasies uitgemaak en 'n relatiewe belangrikheid van 9% getoon. P. vitico/a (takson 2) is meestal uit die nodus en internodus geïsoleer. lnokulasies van gesonde, jong wingerdweefsel het bevestig dat takson 2 'n virulente patogeen is en dat die takson eerder 'n latente patogeen as 'n endofiet is. In teenstelling hiermee is takson 1 'n ware endofiet en 'n onbelangrike patogeen op wingerd. Die ware identiteit van die veroorsakende organisme van streepvlek is ondersoek deur plantmateriaal vanaf 58 verskillende wingerde in die wingerproduserende gebiede van die Wes-Kaap te versamel. P. vitico/a is in wingerdmateriaal vanaf Lutzville tot Swellendam aangetref, maar nie in die Oudtshoorn en Oranjerivier wingerd produserende gebiede nie. Diaporthe perjuncta (takson 1), P. vitico/a (takson 2), takson 3 en P. amygdali is in die Suid Afrikaanse wingerdisolate geïdentifiseer. P. amygdali word met lootverskroeiing van perske bome in die V.S.A. geassosieer. Die Australiese isolaat wat benoem is as takson 4, is met die huidige ondersoek gevind om 'n spesie van Libertella te wees. Takson 4 is daarvolgens uit die P. vitico/a-kompleks gelaat. 'n Italiaanse isolaat het 'n nuwe spesie van Phomopsis op wingerd verteenwoordig en is vervolgens as takson 5 beskryf. Spesie-onderskeiding is op morfologiese en kulturele eienskappe, staminokulasies en die vorming van die teleomorf in vitro gebaseer. Die identiteit vanelke morfologiese takson is met behulp van filogenetiese analises van die nukleêre ribosomale DNS intern transkriberende spasieerders (ITS 1 en ITS2) en die 5' punt gedeeltelike nukleotied volgorde van die mitochondriale klein subeenheid (mtSSU) bevestig. P. amygdali is slegs een keer geïsoleer en blyk van minder belang in die siektekompleks te wees. Takson 1 (Diaporthe perjuneta) en takson 3 het ook min voorgekom en is nie-patogenies, wat hul nie-funksionele rol in streepvleksiekte aandui. Takson 2 (P. viticola) is algemeen geïsoleer en kom wyd verspreid voor. Hierdie takson is geassosieer met die tipiese siektesimptome en is ook patogenies. Morfologies stem takson 2 met P. viiicola ooreen en is ook geneotipifiseer in hierdie studie. Takson 2 is meestal vanaf die ogies en nodusse geïsoleer, wat daarop dui dat hierdie belangrike setels is waar die swam tydens die winter oorleef. Die molekulêre data toon aan dat takson 3 en P. amygdali nie gasheerspesifiek tot wingerd is nie. Die swamdoders wat tans teen streepvlek gebruik word, is met die nuwe strobilurin swamdoders vergelyk. Die effek van nege swamdoders (azoksistrobin, flusilasool, folpet, fosetyl-Al + mancozeb, kresoxirn-metiel, mankozeb, penconasool, spiroksamien en trifloksistrobin) is in vitro op die inhibisie van miseliumgroei getoets. Die volgende EKso-waardes (g/ml) is verkry: azoxystrobin (0.350), flusilasool (0.007), folpet (4.489), fosetiel-Al + mankozeb (3.925), kresoxirn-metiel (l.665), mankozeb (2.891), penkonasool (0.023), spiroksamien (0.321) en trifloxystrobin (0.051). Azoxystrobin, folpet, kresoxim-rnetiel, mankozeb, propineb en trifloksistrobin is ook in vitro getoets vir hul inhibisie op spoorontkieming. Die volgende EKso-waardes is verkry: azoxystrobin (0.123), folpet (0.510), kresoxim-metiel (0.0037), mankozeb (0.250), propineb (0.156) en trifloxystrobin (0.003). Die resultate vervat in deel 4 toon dat die strobilurin swamdoders die miseliumgroei en spoorontkieming van P. viticola inhibeer. Toetsing in die veld word egter benodig om die effektiwiteit van die middels te bevestig. In hierdie studie is taksa I, 3 en P. amygdali selde geïsoleer, wat aangedui het dat hierdie taksa 'n minder belangrike rol in die P. viticola-kompleks speel.

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Knowledge of the presence of Botrytis cinerea in morphological parts of bunches and leaves of grapevine would help to find a reliable, sensitive, and specific assay to verify the actual occurrence of latent infection, and to plan strategies for the effective control of B. cinerea bunch rot. The aim of this study was (i) to determine natural B. cinerea infection at specific sites in leaves and bunches of grapevine at different phenological stages, and (ii) to determine resistance in the morphological parts to disease expression. Bunches and leaves of the wine grape cultivar Merlot and the table grape cultivar Dauphine, were collected at pea size, bunch closure and harvest from five vineyards in the Stellenbosch and De Dooms regions respectively. The material was divided into two groups and sealed in polythene bags. The bags were lined with wet paper towels to establish high relative humidity. Leaves and bunches incubated in one group of bags were first treated with paraquat in order to terminate active host responses. These treatments provided conditions that facilitated disease expression under two host resistance levels by different inocula during the period of moist incubation. Disease expression was positively identified by lesion development, and the formation of sporulating colonies of B. cinerea at a potential infection site. Sites in leaves were the blades and petioles. Sites in bunch parts were rachises, laterals and pedicels, and on berries sites were the pedicel-end, cheek and style-end. In Dauphine, the various sites were at all stages classified as resistant to moderately resistant. However, at pea size and bunch closure, in spite of their resistance, nearly all the sites carried high to very high inoculum levels. The only exception was the berry cheek, which carried intermediate inoculum levels at pea size, and low inoculum levels at bunch closure. In nearly all sites, inoculum levels were lower at harvest. The decrease was the most prominent in petioles, rachises, laterals, pedicels and the pedicel-end of the berry. All these sites carried intermediate to low inoculum levels at harvest. In Merlot, sites constantly exibited a resistant reaction, except for the pedicel and pedicel-end of the berry, which changed from resistant at the early developmental stages to susceptible at harvest. Inoculum levels decreased during the season in the rachises and laterals, but were constantly high during the season in the pedicel and pedicel-end of the berry. According to this pattern of natural occurrence, B. cinerea fruit rot in these vineyards was not caused by colonisation of the pistil, and subsequent latency in the style end of grape berries. However, fruit rot was primarily caused by colonisation of the pedicel, and subsequent latency in the pedicel or pedicel-end of the berry. These findings furthermore support the hypothesis of increased host resistance during development, but also indicate that in the Western Cape province, inoculum in vineyards is abundant during the early part of the season, and less abundant later in the season. More information is therefore needed on the behaviour of the different types of B. cinerea inocula on the different morphological parts of grapevine to validate the pathway described for natural B. cinerea infection in vineyards. The penetration and disease expression at the different morphological parts of bunches of two grape cultivars (Dauphine and Merlot) under conditions simulating natural infection by airborne conidia was therefore investigated. The two cultivars did not differ in resistance of the berry cheek, which was at all stages classified as resistant. However, in Dauphine, latent inoculum levels in berry cheeks declined from intermediate at pea size to low at the following stages, whereas in Merlot, levels were intermediate during pea size and at harvest. Some differences between cultivars were found in the resistance of the structural bunch parts, and of their latent inoculum levels. In Dauphine, the rachis reacted susceptible at pea size, and was classified moderately resistant later in the season. Laterals and pedicels were moderate resistant at pea size, and resistant at later stages. Inoculum levels in rachises, laterals and pedicels were high at pea size, but intermediate at bunch closure and at harvest. The finding that B. cinerea infected and naturally occurred more commonly in the tissues of immature than mature bunches, that the structural parts of the bunch carried more B. cinerea than the berry cheek, and that these infections may be more important in B. cinerea bunch rot than infection of the cheek or the style end, suggest that emphasis should be placed on the disease reaction of the pedicel and related parts of immature bunches rather than on the berry. The resistanc-e reaction of leaf blades, petioles, internodes and inflorescences on cuttings, compared to those on older shoots from the vineyard were therefore investigated. In the case of vinelets, leaf blades, petioles, internodes and inflorescences were all classified susceptible to highly susceptible. The different parts furthermore all carried very high latent inoculum levels. In vineyard shoots the petioles and inflorescences showed resistance, and carried intermediate to latent inoculum levels. This finding suggests that leaf blades are not appropriate parts for studying the behaviour of inoculum of B. cinerea and host responses in grape bunches. In stead, petioles and inflorescences of vineyard shoots should be used for this purpose.
AFRIKAANSE OPSOMMING: WEERSTAND TEEN BOTRYTIS CINEREA IN MORFOLOGIESE DELE VAN BLARE EN TROSSE VAN WINGERD Kennis oor die teenwoordigheid van Botrytis cinerea in morfologiese dele van wingerd word benodig vir die ontwerp van 'n betroubare, sensitiewe en spesifieke toets vir die bevestiging van latente infeksies, en vir die implementering van strategieë vir die effektiewe beheer van B. cinerea-vrot. Die doel van hierdie studie was om (i) natuurlike B. cinerea infeksie by spesifieke areas in blare en trosse van wingerd te bepaal, en (ii) om weerstand teen siekte-uitdrukking in hierdie morfologiese dele vas te stel. Trosse en blare van die wyndruif kultivar Merlot en die tafeldruif kultivar Dauphine, is by ertjiekorrel, tros-toemaak en oes in vyf wingerde in die Stellenbosch- en De Doomsomgewing, onderskeidelik, versamel. Die materiaal is in twee groepe verdeel en in polietileen sakkies verseël. Die sakkies is met klam papierdoekies uitgevoer om sodoende hoë relatiewe humiditeit te verseker. Blare en trosse wat in die een groep geïnkubeer is, is eers met paraquat behandel om aktiewe gasheerreaksies te beëindig. Hierdie behandelings het toestande geskep wat gedurende die periode van vogtige inkubasie gunstig was vir siekteontwikkeling deur verskillende inokula by twee gasheer-weerstandsvlakke. Siekteuitdrukking is positief geïdentifiseer deur letsel-ontwikkeling en die vorming van sporuierende kolonies van B. cinerea by 'n potensiële infeksie-area. Dele waarop in die blare gekonsentreer is, was die blaarskyf en -steel. In die trosse was die dele die rachis, lateraal en korrelsteel, en op korrels was dit die korrelsteel-end, wang en styl-end. In Dauphine is die verskillende dele tydens al die fenologiese stadia as weerstandbiedend tot matig weerstandbiedend geklassifiseer. Die verskillende dele her egter, ten spyte van hul weerstandbiedendheid, hoë tot baie hoë inokulumvlakke by ertjiekorrel- en tros-toemaakstadium gedra. Die enigste uitsondering was die korrelwang, wat 'n middelmatige inokulumvlak by ertjiekorrel, en 'n lae inokulumvlak by tros-toemaak, gedra het. Die inokulumvlakke was in byna al die dele laer by oes. Die afname in inokulumvlakke was die prominentste in die blaarstele, rachi, laterale, korreisteie en die korrelsteel-end van die korrel. Al hierdie dele het 'n middelmatige tot lae inokulumvlak by oes gehad. In Merlot was die dele konstant weerstandbiedend, behalwe vir die korrelsteel en die korrelsteel-end van die korrel, wat gewissel het van weerstandbiedend by die vroeë ontwikkelingstadia, tot vatbaar by oes. lnokulumvlakke in die rachis en lateraal het gedurende die seisoen afgeneem; maar was deur die seisoen konstant hoog in die korrelsteel en korrelsteel-end van die korrel. Volgens die patroon van natuurlike voorkoms, word B. cinerea-vrot in hierdie wingerde nie deur kolonisasie van die stamper, en die daaropvolgende latensie in die styl-end van die korrels, veroorsaak nie. Vrot word egter primêr deur kolonisasie van die korrelsteel, en die daaropvolgende latensie in die korrelsteel of korrelsteel-end van die korrel, veroorsaak. Hierdie bevindinge ondersteun die hipotese van toenemende gasheerweerstand gedurende ontwikkeling, en dui ook daarop dat inokulumvlakke in wingerde in die Wes-Kaap provinsie volop is gedurende die eerste deel van die seisoen, en minder volop is later in die seisoen. Meer inligting word dus benodig aangaande die gedrag van die verskillende inokulum tipes van B. cinerea op die verskillende morfologiese dele van wingerd, ten einde die infeksieweg vir natuurlike B. cinerea infeksie in wingerde te bevestig. Die vestiging van latente infeksies in die verskillende morfologiese dele van trosse van twee kultivars (Dauphine en Merlot), onder toestande wat natuurlike infeksie deur luggedraagde konidia simuleer, is dus ondersoek. Die twee kultivars se weerstand in die korrelwang het nie verskil nie en is by alle fenologiese stadia as weerstandbiedend geklassifiseer. Die latente inokulumvlakke in die korrelwang van Dauphine het egter van middelmatig by ertjiekorrel, tot laag in die daaropvolgende stadia afgeneem, terwyl die vlakke in Merlot middelmatig by ertjiekorrel en oes was. Verskille tussen die twee kultivars is gevind ten opsigte van die weerstand in die trosdele, asook hulle latente inokulumvlakke. Die rachis van Dauphine was by ertjiekorrel vatbaar, en matig weerstandbiedend later in die seisoen. Die lateraal en korrelsteel was matig weerstandbiedend by ertjiekorrel en weerstandbiedend by latere stadia. lnokulumvlakke in rachi, laterale en korreisteie was hoog by ertjiekorrel, maar middelmatig by tros-toemaak en oes. Die bevindinge dat B. cinerea natuurlik meer algemeen in die weefsel van onvolwasse trosse voorgekom en laasgenoemde meer algemeen geïnfekteer het, dat B. cinerea se voorkoms hoër was in die morfologiese dele van die tros as in die korrelwang, en dat hierdie infeksies van groter belang in B. cinerea-vrot mag wees as infeksie van die wang of styl-end, dui daarop dat klem gelê moet word op die siektereaksie van die strukturele dele van onvolwasse trosse, eerder as van die korrel. Die weerstand van blaarskywe, blaarstele, internodes en blomtrossies van steggies, in vergelyking met die op ouer lote in wingerde, is dus ondersoek. Blaarskywe, blaarstele, internodes en blomtrossies van steggies is almal as vatbaar tot hoogs vatbaar geklassifiseer. Die verskillende dele het verder ook almal baie hoë latente inokulumvlakke gedra. By die ouer lote van wingerde het die blaarstele en blomtrossies weerstandbiedend vertoon, en middelmatige latente inokulumvlakke gedra. Hierdie bevindinge dui daarop dat blaarskywe nie die ideale morfologiese deel is vir gedragstudies van B. cinerea in druiwetrosse nie. Blaarstele en blomtrossies van ouer lote moet eerder vir die doel gebruik word.

Thesis (MScAgric)--University of Stellenbosch, 2000.
ENGLISH ABSTRACT: Petri grapevme decline, also known as black goo, slow die-back and Phaeoacremonium grapevine decline, causes significant losses of young vines worldwide. Species of Phaeoacremonium, Phaeomoniella chlamydospora and related genera are associated with this grapevine disease. This study investigates the Phaeoacremonium-complex and Phaeomoniella chlamydospora, focussing on the species isolated from grapevines. Fungicide sensitivity of Pa. chlamydospora and the possibility of employing molecular techniques for the detection of Pa. chlamydospora in grapevines were also investigated. In an overview of the literature on Petri grapevine decline the disease history and the relatedness of Petri grapevine decline to esca is discussed. Petri grapvine decline occurs in propagation material or young vines. Infected material can appear asymptomatic and therefore the possibilities of molecular techniques for identification were also investigated in the literature. In South Africa Pa. chlamydospora is the dominant organism causing Petri grapevine decline and therefore different fungicides were evaluated to control this fungus. Six isolates of Pa. chlamydospora, from Stellenbosch, Wellington, Somerset West and Malmesbury of Western Cape province, South Africa, were screened against twelve fungicides testing their effect on mycelial inhibition in vitro. These fungicides included benomyl, chlorothalonil, fenarimol, fosetyl-Al, iprodione, kresoxim-methyl, mancozeb, metalaxyl, prochloraz manganese chloride, quintozene, tebuconazole and thiram. Results provided the base-line sensitivity of South African isolates of Pa. chlamydospora. Benomyl, fenarimol, kresoxim-methyl, prochloraz manganese chloride and tebuconazole were the most effective (with EC50 values ranging from 0.01 to 0.05 ug/ml) for inhibiting mycelial growth of Pa. chlamydospora in vitro. This in vitro test gave a good indication of which fungicides could be selected for further studies in glasshouses and nurseries. The molecular phylogeny of Phaeoacremonium and Phaeomoniella isolates from grapevines of South Africa, or isolates obtained from the Centraalbureau voor Schimmelcultures (CBS) in the Netherland, were investigated. Sequence data were created from the rONA region and partial B-tubulin gene of 33 of these isolates using the PCR technique. This sequence data were analysed with PAUP* version 4.Ob2a. An analysis of the sequence data confirmed the genus Phaeomoniella to be distinct from Phaeoacremonium (Pm.) based on DNA phylogeny. Although morphologically similar, the species status of Pm. aleophi/um and Pm. angustius was confirmed with DNA phylogeny and cultural characteristics. Pm. aleophilum has an optimum growth rate at 30°C and the ability to grow at 35°C, where as Pm. angustius has an optimum growth rate at 25°C and cannot grow at 35°C_ Pm. viticola was shown to be synonymous with Pm. angustius, and a new species, Pm. mortoniae, was newly described from grapevine occurring in California. Futhermore, Pm. aleophilum was newly reported from South Africa and grapevine isolates thought to be Pm. inflatipes were all re-identified as Pm. aleophilum. These findings therefore also shed some doubt on the possible role of Pm. inflatipes in Petri grapevine decline. It was confirmed that Pa. chlamydospora, Pm. aleophilum and Pm. angustius are the species involved in Petri grapevine decline. Pm. mortoniae was isolated from grapevines, but its pathogenicity should still be confirmed and the role of Pm. injlatipes in Petri grapevine decline remains unclear. Pa. chlamydospora has been routinely isolated from symptomless propagation and nursery material. Because the disease can take years to develop, it is crucial that healthy propagation material is used at planting. Pa. chlamydospora is a slowgrowing fungus, and positive identification from symptomless grapevine tissue can take up to 4 wks. The possibility of employing molecular techniques for the detection of Pa. chlamydospora in apparently healthy grapevines was investigated. Speciesspecific primers (PCLI and PCL2) based on the regions ITSI and ITS2 were designed for Pa. chlamydospora. These primers were highly sensitive and amplification was achieved from genomic DNA of Pa. chlamydospora from as low as 16 pg. Phaeoacremonium spp., related genera and common fungal taxa from grapevines were tested with these primers, but positive amplification was achieved for Pa. chlamydospora only. The presence of Pa. chlamydospora in symptomless grapevine tissue culture plants was confirmed by PCR within 24 hours. These primers therefore allow rapid and accurate identification of Pa. c~lamydospora. Testing on a larger scale with nursery material should be conducted to determine the feasibility of using these species-specific primers in the grapevine industry.
AFRIKAANSE OPSOMMING: Petri-terugsterwing van jong wingerde, ook algemeen bekend as "black goo" en Phaeoacremonium-terugsterwing, veroorsaak wêreldwyd groot geldelike verliese in die wingerdbedryf. Spesies van Phaeoacremonium, Phaeomoniella chlamydospora en verwante genera word met hierdie wingerdsiekte geassosieer. In die tesis word In oorsig gegee van die geskiedenis van hierdie siekte, die verwantskap tussen Petriterugsterwing en esca, en moontlike maniere van siektebestuur. Swamme wat by die siektekompleks betrokke is, kan in simptoomlose plantweefsel voorkom en daarom is die moontlikhede van die gebruik van molekulêre tegnieke vir swamidentifikasie in oënskou geneem. In Suid-Afrika is Pa. chlamydospora die dominante swam wat met Petriterugsterwing geassosieerword, gevolglik is verskillende fungisiedes vir die chemiese beheer van Pa. chlamydospora geëvalueer. Ses isolate van Pa. chlamydospora, versamel vanaf verskillende areas in die Wes-Kaap provinsie, is in dié studie gebruik. Benomyl, chlorothalonil, fenarimol, fosetyl-Al, iprodione, kresoxim-methyl, mancozeb, metalaxyl, prochloraz manganese chloride, quintozene, tebuconazole en thiram se effek op miselium inhibisie van Pa. chlamydospora is in vitro geëvalueer. Benomyl, fenarimol, kresoxim-methyl, prochloraz manganese chloride en tebuconazole was die mees effektiewe middels. Die effektiewe konsentrasie waarby 50% van die miselium groei geïnhibeer is (EKso),was tussen 0.01 en 0.05 ug/ml vir die mees effektiewe groep middels. Benomyl, fenarimol, kresoxim-methyl, prochloraz manganese chloride en tebuconazole het in vitro goeie potensiaal getoon, en verder toetse moet in vivo uitgevoer word. 'n Molekulêre studie is van Phaeoacremonium en Phaeomoniella isolate; verkry uit Suid-Afrikaanse wingerde, of vanaf die "Centraalbureau voor Schimmelcultures" (CBS) van Nederland; gedoen. Deur van die PKR tegniek gebruik te maak, is die basispaaropeenvolgingsdata van 33 isolate, van die ITSl, 5.8S, ITS2 rDNA area en die gedeeltelike B-tubullen geen verkry. Gekombineerde molekulêre data het die teorie ondersteun dat Phaeomoniella (Herpotrichiellaceae) gedistansieerd is van Phaeoacremonium (Magnaporthaceae). Pm. aleophilum en Pm. angustius was morfologies moeilik onderskeibaar, maar kon op grond van molekulêre data en kulturele eienskappe onderskei word. Pm. aleophilum se optimum groeitemperatuur was by 30°C en die swam besit die vermoë om by 35°C te groei. Pm. angus/ius se optimum groeitemperatuur was by 25°C, maar het nie by 35°C gegroei nie. 'n Studie van molekulêre en kulturele eienskappe het getoon dat Pm. angus/ius en Pm. viticola sinoniem is. 'n Nuwe spesie, Pm. mortoniae, wat uit wingerde van Kalifornie geïsoleer is, is beskrywe. Verder is Pm. aleophilum die eerste keer in Suid-Afrikaanse wingerde aangetref en Pm. tnflatipes isolate, wat vanuit wingerde geïsoleer is, is almal met molekulêre data gewys om Pm. aleophilum te wees. Hierdie bevindinge trek die rol van Pm. inflatipes in Petri-terugsterwing van wingerde in twyfel. Phaeomoniella chlamydospora IS m voortplantingsmateriaal en kwekerystokkies opgespoor. Omdat dit jare kan duur voordat siektesimptome ontwikkel, is dit belangrik om vroegtydig te weet of jong stokkies met Pa. chlamydospora geïnfekteer is. Pa. chlamydospora groei baie stadig en positiewe identifikasie van simptoomlose infeksies duur tot vier weke. Die toepassing van molekulêre tegnieke vir die vinnige identifikasie van Pa. chlamydospora in wingerde is dus ondersoek. Spesie-spesifieke oligonukleotiedes (PCU en PCL2) is vir Pa. chlamydospora ontwerp. Hierdie oligonukleotiedes is uiters sensitief en genomiese DNA van Pa. chlamydospora is van so laag as 16 pg geamplifiseer. Phaeoacremonium spp., verwante genera en algemene swamme vanuit wingerdmateriaal is met die oligonukleotiedes getoets, maar positiewe amplifikasie was slegs met Pa. chlamydospora moontlik. Die teenwoordigheid van Pa. chlamydospora is binne 24 uur in asimptomatiese wingerd weefselkultuurplantjies bevestig. Hierdie oligonukleotiedes identifiseer Pa. chlamydospora vinnig en akkuraat en toetsing op 'n groter skaal moet vervolgens met kwekerymateriaal onderneem word.

Thesis (MScAgric)--University of Stellenbosch
ENGLISH ABSTRACT: An understanding of the infection pathways of Botrytis cinerea in grape bunches will help to combat this devastating pathogen of grape. Many studies have been done to determine the possible infection pathways of B. cinerea. Most of these studies made use of artificial inoculations that deposit groups of conidia on the plant surface. The deposition of clusters of conidia is not a common phenomenon in nature. The aim of this study was to investigate the infection pathways of (i) naturally- as well as (ii) artificially inoculated B. cinerea conidia during all the phenological stages of three wine grape cultivars, and to compare the (iii) pathogenicity and virulence, on grape and nectarine fruit, of isolates obtained from different host plants. In the natural infection study the occurrence of Botrytis cinerea and subsequent disease expression at different positions in bunches of wine grapes (cultivars Chenin Blanc, Shiraz and Chardonnay) was determined from 1999 to 2001. Different techniques were used to detect viable inoculum at different positions (rachises, laterals, pedicels, and the peicel end, cheek and style end of berries) in bunches. Isolations were made on Kerssies' B. cinerea selective medium, or bunches were used untreated, or treated with paraquat. Paraquat was used to terminate host resistance and to promote the development of the pathogen from the tissues. The material was used untreated to detect the pathogen on the surface, or were surface-sterilized to detect mycelia (latent infection) in the tissue. In the artificial inoculation study, bunches of wine grapes (cultivars Chenin Blanc, Chardonnay and Shiraz) at pea size, bunch closure, and harvest were dusted with dry conidia of Botrytis cinerea in a settling tower and incubated for 24 h at high relative humidity (±93%). Following incubation, the bunches were divided in two groups. The one group was surface-sterilised in 70% ethanol for 5 s, the other group was left untreated. Bunches of the sterile group, and from the untreated group were used for isolation. From each bunch rachis segments, laterals, pedicels and berry skin segments (from the pedicel-end and cheek) were removed. The sections were placed in Petri dishes on Kerssies' B. cinerea selective medium and on a water agar medium supplemented with paraquat, and incubated at 22°C under diurnal light. Occupation by the pathogen was positively identified by the formation of sporulating colonies of B. cinerea on the different tissues. Lastly, in the virulence and pathogenicity experiment on grape and nectarine fruit Botrytis cinerea isolates, which were obtained from different host plants, were compared by simulating natural infection. Cold-stored fruit, considered highly susceptible to B. cinerea were therefore inoculated with single, airborne conidia of the pathogen. Different tests were conducted to assess surface penetration and lesion formation. Isolations were made from fruit skins on Kerssies' B. cinerea selective medium. Nectarine fruit were treated with paraquat, and grape berries were frozen for 1 h at -12°C. Paraquat and freezing were used to terminate host resistance and to promote the development of the pathogen from the tissues. In the natural infection studies B. cinerea occurred in a consistent pattern in bunches of the three cultivars. B. cinerea consistently developed from the tissue of the rachis, laterals, pedicel and pedicel-end, but not from the berry cheek. The rachis, lateral and pedicel contained much higher levels of B. cinerea than any position on the berry. Furthermore, the pathogen consistenly occurred at relatively high levels on the rachises throughout the season. Collectively, the data showed that in the Western Cape province, B. cinerea occured more regularly in wine grape bunches during the early part of the season, than later in the season. The data of the artificial studies confirmed the findings made with the natural infection studies. In these experiments the pathogen resided more often on the structural bunch parts than on the berries. Overall, the isolation studies revealed that conidia occurred predominantly on the rachis. The incidence of B. cinerea was furthermore constantly high in the inner bunch after each inoculation, and in bunches of different maturities. The data therefore indicated that, when available, conidia penetrated loose and tight clustered bunches in a similar way. Finally, in the virulence and pathogenicity experiments the results showed clearly that no host specialisation exists in the B. cinerea isolates used in this study. From these studies it is clear that in the Western Cape province B. cinerea occurs more readily in the inner structural parts of the bunches and more so during the earlier parts of the season. These findings should be considered when planning and implementing disease control programmes.
AFRIKAANSE OPSOMMING: INFEKSIEWEË VAN BOTRYTIS CINEREA OP GESELEKTEERDE WYNDRUIF KULTIVARS Indiepte kennis van die infeksieweë van Botrytis cinerea op druiwetrosse word benodig vir die beheer van dié vernietigende patogeen van druiwe. Vele studies is al gedoen om die moontlike infeksieweë van die swam op druiwe trosse te ondersoek. Die meeste van die studies het gebruik gemaak van kunsmatige inokulasie tegnieke waar die konidia van die swam in groepe op die korreloppervlak gedeponeer is. In die natuur is dit 'n rare verskynsel dat konidia in groepe op die korreloppervlak land. Die doel van die studie was om die infeksieweë van B. cinerea op drie wyndruif kultivars te ondersoek wat (i) natuurlik- en (ii) kunsmatig geïnokuleer is met konidia gedurende al die fenologiese stadia, en om die (iii) virulensie en patogenisisteit van isolate wat van verskillende gashere verkry is, op druiwe en nektariens te vergelyk. In die natuurlik-geïnokuleerde druiwe is die voorkoms van B. cinerea en die gevolglike siektevoorkoms op verkillende posisies in trosse van wyndruiwe (Chenin Blanc, Chardonnay, Shiraz) gedurende 1999 tot 2001 bepaal. Verskillende tegnieke is gebruik om lewensvatbare inokulum by verskillende posisies (ragis, lateraal, pedisel en pedisel-end van die korrel) in die tros waar te neem. Isolasies is op Kerssies' B. cinerea selektiewe medium gemaak, of trosse is onbehandeld gebruik, of behandel met paraquat. Paraquat is gebruik om die gasheer se natuurlike weerstand te verlaag en om die ontwikkeling van die patogeen te bevorder. Die plantmateriaal is onbehandeld gelaat om die patogeen op die oppervlak waar te neem, of die oppervlak is gesteriliseer om die latente myselium in die weefsel waar te neem. In die kunsmatige inokulasiestudies is trosse, van wyndruiwe (Chenin Blanc, Chardonnay, Shiraz), geïnokuleer met droë spore, van B. cinerea, in 'n inokulasietoring en die plantmateriaal is dan geinkubeer vir 24 h by 'n hoë relatiewe humiditeit (93%). Na die inkubasie proses is die trosse in twee groepe verdeel. Die een groep druiwe het oppervlak sterilisasie ondergaan in 70% etanol vir 5 s, en die ander groep was onbehandeld gelaat. Trosse van die onbehandelde en gesteriliseerde groep druiwe is gebruik vir isolasies. Vanuit elke tros is daar segmente van die ragis, laterale, pediselle en korrels (van die pedisel-end en wang gedeeltes) geïsoleer. Die segmente is in Petri bakkies met Kerssies' B. cinerea selektiewe medium en op water agar medium, wat paraquat bevat het, geïsoleer en geïnkubeer onder 'n 12 h dagligperiode teen 22°C. Die patogeen is positief geïdentifiseer deur sporuierende kolonies op die onderskeie weefseltipes. Laastens, in die virulensie- en patogenisiteitsproewe op druiwe en nektariens is verskillende isolate van B. cinerea, verkry vanaf verskillende gasheerplante, vergelyk deur natuurlike inokulasie toestande na te boots. Koue opgebergde vrugte, wat beskou word as hoogs vatbaar vir die infeksie van B. cinerea, is geïnokuleer met droë, enkel luggedraagde spore van die patogeen. Verskillende toetse is gedoen om die oppervlak penetrerende en letselvormende vermoëns van die onderskeie isolate te toets. Isolasies is van die skille van die vrugte gemaak en op Kerssies' B. cinerea selektiewe medium geplaas. Die nektarienvrugte is met paraquat behandel en die druifkorrels is gevries vir 1 h teen -12°C. Paraquat en bevriesing is gebruik om die gasheer se weerstand te verlaag en om die ontwikkeling van die patogeen te bevorder. In die natuurlik-geïnokuleerde studies het B. cinerea 'n konstante patroon getoon in die trosse van die drie verskillende wyndruif kultivars. B. cinerea het konstant ontwikkel uit die ragis, laterale, pedisel en pedisel-end, maar selde uit die korrelwang. Die ragis, lateral en pedisel dele het baie hoër vlakke van van die swam bevat as enige deel op die korrel. Die patogeen het ook konstant volop deur die hele seisoen op die ragis voorgekom. Gesamentlik wys die data dat, B. cinerea in wyndruiwe, in die Wes Kaap provinsie, meer geredelik vroeër in die seisoen voorkom, eerder as later. Data van die kunsmatige inokulasiestudies het die bevindinge van die natuurlike inokulasiestudies tot 'n groot mate bevestig. In dié studies het die patogeen meer geredelik die strukturele dele van die tros, eerder as op die korrels, bewoon. Oor die algemeen het die isolasieproewe gewys dat die konidia meer op die ragis voorkom as op enige ander deel. Die voorkoms van B. cinerea was ook oor die algemeen baie hoër in die strukturele dele van die tros, as op die korrel self. Die verskynsel het onder trosse van verskillende ontwikkelingsvlakke voorgekom. Die data het dus ook gewys dat konidia, wanner dit beskikbaar is, minder- sowel as meer kompakte trosse op 'n soortgelyke manier penetreer. Laastens, in die virulensie en patogenisiteitseksperimente het die resultate duidelik gewys dat daar geen gasheer spesifieke gedrag onder B. cinerea isolate is nie. In die studies het dit duidelik na vore gekom dat, B. cinerea meer geredelik in die strukturele binne dele van die wyndruif tros, in die Wes Kaap provinsie voorkom. En so ook eerder aan die begin van die seisoen, as later in die seisoen. Dié kennis moet in aanmerking geneem word by die beplanning en implementering van siektebeheerprogramme.

Thesis (MSc)--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: Plants are constantly exposed to biotic and abiotic stress inducing factors that threaten their existence. Biotic factors such as pathogens are the cause of huge yield losses to crop plants worldwide with fungal pathogens debatably constituting the worst damage. Fungal pathogens such as Botrytis cinerea, which has a wide host range, release cell wall degrading enzymes called endopolygalacturonases (ePGs) during plant infection. These ePGs break down the pectin component of the cell wall, thus providing an entry route, as well as nutrients for the fungus. Plants have evolved mechanisms to counteract and suppress the action of the ePGs. This is achieved through the action of cell wall associated proteins called polygalacturonaseinhibiting proteins, PGIPs. PGIPs directly inhibit ePGs and their inhibitory action also prolongs the existence of longer chain oligogalacturonide residues which are believed to elicit a cascade of defence responses. In grapevine, a PGIP encoding gene, VvPGIP1, was previously isolated and characterised. VvPGIP1, as well as nine non-vinifera grapevine PGIPs have been expressed in tobacco and shown to be potent antifungal proteins that caused the transgenic tobacco to have strong resistance phenotypes against Botrytis in whole plant infection assays. Following on the tobacco study, two of the non-vinifera PGIPs were expressed in cultivars of the susceptible Vitis vinifera. Characterisation of the putative transgenic population showed that transgene integration was successful, the transgenes were being expressed and there were at least 29 transgenic lines with independent integration events. The transgenic lines were confirmed to have active PGIPs (transgene-derived) in their leaves. Crude protein extracts from 22 lines exhibited 100% inhibition against crude B. cinerea PGs (BcPGs). The plant lines with positive transgene integration, expression, independent integration events and exhibiting 100% transgene-derived PGIP activity were further selected for whole plant and detached leaf antifungal assays where they were challenged with B. cinerea. The whole plant infection assay showed that expression of the non-vinifera PGIPs in V. vinifera promotes susceptibility to B. cinerea, not resistance. This surprising result could perhaps be explained by a quicker and stronger recognition between the pathogen and the host and the stronger activation of defence responses in the host. A more active hypersensitive response in the host would benefit Botrytis being a necrotroph. The type of lesions and the onset and speed of lesion development observed on the transgenics lines versus the wild type support this possibility. Knowledge gaps with regards to the efficiency of the ePG inhibition by the nonvinifera PGIPs during infection of grapevine tissue; the potential changes that might be caused by expressing PGIPs in a grapevine host with a native PGIP with high homology to the transgenes (including potential gene silencing) and the potential impact on defence signalling and defence responses all provides further avenues of study to elucidate this very interesting phenotype further. Overall, this study provides a comprehensively characterised population of transgenic plants that provides useful resources for in vivo analysis of PGIP function in defence, where the host plant harbours a native copy of the PGIP encoding gene.
AFRIKAANSE OPSOMMING: Plante word voortdurend blootgestel aan biotiese en abiotiese faktore, wat stres veroorsaak en hul bestaan bedreig. Biotiese faktore, soos patogene, veroorsaak groot verliese in wêreldwye gewasopbrengste, met swampatogene wat moontlik die grootste skade veroorsaak. Swampatogene, soos Botrytis cinerea, wat ‘n wye reeks gasheerplante kan infekteer, stel selwand-afbrekende ensieme tydens plantinfeksie vry, wat as endo-poligalakturonases (ePG’s). bekend staan. Hierdie ePG’s breek die pektienkomponent van die selwand af, wat gevolglik as ‘n ingangspunt dien,asook voedingstowwe vir die swam verskaf. Plante het meganismes ontwikkel om die aktiwiteit van hierdie ePG’s te bekamp en te onderdruk. Die aktiwiteit van die selwand-geassosieërde proteïene, genaamd poligalakturonase-inhiberende proteïene (PGIP’s), speel hier ‘n rol. PGIP’s inhibeer ePG’s direk en hul inhiberende aktiwiteit verleng ook die bestaan van langketting oligogalakturoniedresidu’s, wat blykbaar ‘n kaskade van weerstandsreaksies kan inisieer. ‘n PGIP-koderende geen, VvPGIP1, is voorheen uit wingerd geïsoleer en gekarakteriseer. VvPGIP1, asook nege nie-vinifera wingerd-PGIP’s is voorheen in tabak uitgedruk en bevestig as proteïene met sterk anti-swamaktiwiteit, soos bevestig deur die bevinding dat die transgeniese tabak ‘n weerstandsfenotipe teen Botrytis in heelplant-infeksietoetse het. Ná die tabakstudie is twee van die nie-vinifera PGIP’s uitgedruk in vatbare V. vinifera-kultivars. Karakterisering van die vermeende transgeniese bevolking het getoon dat die transgeen-integrasie suksesvol was, dat die transgeen uitgedruk word en dat daar ten minste 29 transgeniese lyne met onafhanklike integrasie gebeurtenisse geskep is. Daar is verder bevestig dat die transgeniese lyne aktiewe PGIP’s (transgeen-afkomstig) in hul blare het. Ongesuiwerde proteïenekstrakte van 22 lyne het 100% inhibisie teen ‘n mengsel van ongesuiwerde B. cinerea PGs (BcPGs) getoon. Die plantlyne met positiewe transgeenintegrasie en -uitdrukking, asook onafhanklike integrasiegebeure en wat 100% transgeen-afkomstige PGIP-aktiwiteit getoon het, is verder aan heel-plant en verwyderde blaarswaminfeksies met B cinerea onderwerp. Die heelplantinfeksietoetse het getoon dat uitdrukking van nie-vinifera PGIP’s in V. vinifera ‘n toename, in plaas van ‘n afname, in vatbaarheid teen B. cinerea veroorsaak. Hierdie verbasende resultaat kan moontlik toegeskryf word aan ‘n vinniger en sterker herkenningsreaksie tussen patogeen en gasheer en die moontlike sterker stimulering van weerstandsreaksies in die gasheer. ‘n Meer aktiewe hipersensitiewe reaksie in die gasheer sal tot die voordeel van Botrytis, wat ‘n nektrotroof is, wees. Die tipe letsel, asook die aanvang en spoed van letselontwikkeling wat waargeneem is in transgeniese lyne teenoor die wilde-tipe ondersteun hierdie moontlikheid. Gapings in kennis ten opsigte van die doeltreffendheid van die ePG-inhibisie deur die nievinifera PGIP’s tydens infeksie van wingerdweefsel, die moontlike veranderinge (insluitend ‘n moontlike geenuitdowingseffek) wat veroorsaak kan word deur die uitdrukking van PGIP-gene in ‘n kultivar met ‘n inheemse en baie homoloë PGIP-geen, kon ‘n invloed op weerstandseine en weerstandsreaksies gehad het. Hierdie aspekte lewer verdere studiemoontlikhede om hierdie interessante fenotipe verder te verklaar.Algeheel lewer hierdie studie ‘n breedvoeriggekarakteriseerde bevolking trangeniese plante, wat dien as nuttige hulpbronne vir in vivoanalise van PGIP se funksie in siekteweerstandbiedendheid, veral waar die gasheerplant ‘n inheemse kopie van die PGIP-koderende geen huisves.

The natural infestation level for 1985 of the Japanese beetle, Popillia japonica Newman, in the Shenandoah Valley of Virginia failed to reduce berry quality, yield or shoot growth in a commercial vineyard. Intensive postveraison foliage feeding by Japanese beetle resulted 1n fruit with lower soluble solids and higher total titratable acidity at harvest, but did not affect pH, sugar per berry, berry weight, yield, leaves per vine or shoot length. Intensive previraison feeding also resulted in fruit with higher total titratable acidity. All other parameters were unaffected. In a separate experiment with 0, 10, 20, and 33% leaf removal, no relationship was shown between leaf area loss and soluble solids, total titratable acidity or pH. Data from one season of damage by the beetle indicate that control measures may not be warranted in some years. In a third experiment, grape leaves on potted vines were artificially damaged by removing leaf disks with a paper punch. The leaves showed an increased loss of efficiency (measured in net photosynthesis, Pn) for the remaining tissue as leaf area loss (LAL) increased. This loss of efficiency in the remaining leaf area at low levels of damage was more pronounced after 12 days than after either 1 or 5 days. The additive effect on Pn of both LAL and lowered efficiency predicted the total shutdown of Pn at 60% damage at 1 and 5 days after treatment, but not at 12 days.
Master of Science

Thesis (PhD)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Grapevine leafroll-associated virus-3 is one of ten members of the C/osteroviridae that are known to infect grapevine. Nine of these viruses are associated with grapevine leafroll disease, of which GLRaV-1 and GLRaV-3 are the most important and widespread. Members of the C/osteroviridae are unique amongst the viruses, as it is the only known family whose members encode a heat shock protein 70 kOa homolog (Hsp70h). The Hsp70h is a movement protein (MP) that is required for the active translocation of the virion structure through the plasmodesmata into adjacent cells. Broad-spectrum resistance to unrelated viruses can be obtained by a pathogen-derived resistance (POR) strategy that is based on the expression of a dysfunctional MP in plants. The Hsp70h has two distinct domains. The N-terminal two thirds of the protein is an ATPase domain and shares high homology with the ATPase domains of all Hsp70h proteins from the C/osteroviridae and Hsp70 proteins from the prokaryote and eukaryote kingdoms. Conserved amino acids are found in the ATPase domain and are required for the positioning of the ATP at the catalytic site for ATP hydrolysis. The C-terminal domain is variable and the function of this domain in the Closteroviridae is not known. In prokaryote and eukaryote Hsp70 proteins, the C-terminal domain is required for protein-protein interactions. The American NY-1 isolate of GLRaV-3 has been sequenced and POR strategies have been attempted with the coat protein, divergent coat protein and replicase genes, but not with a dysfunctional form of the hsp70h gene. In this study, double-stranded RNA was isolated from a commercial vineyard with unknown virus status, but with distinct grapevine leafroll symptoms, and from two grapevine sources of known virus status, one with mild and one with severe symptoms. The GLRaV-3 hsp70h gene was amplified by RT-PCR from the dsRNA and the gene sequence was analysed. The hsp70h gene from the three virus sources contained more than 94% nucleotide sequence homology to the NY-1 isolate and the conserved amino acids required for ATPase activity were present. The hsp70h gene isolated from GLRaV-3 from a commercial Stellenbosch vineyard showing clear leafroll symptoms was selected for further work and was subjected to site-directed mutagenesis to engineer four point mutations in the gene. These four mutations resulted in the substitution of Asn for Asp", Gly for Thr1O, Lys for Glu 174 and Asn for Asp 197. The wild type (WT) and mutated (Mut) forms of the hsp 70h genes were cloned into a bacterial expression vector. Expression of both the WT- and Mut-Hsp proteins was achieved, and the protein was expressed in the insoluble inclusion bodies. All attempts to refold and isolate active proteins from the inclusion bodies were unsuccessful. Attempts to increase the concentration of soluble protein within the expressing bacteria were unsuccessful. Due to the lack of active protein, biochemical tests on the ATPase activity of the WT- and Mut-Hsp proteins could not be conducted. The wt- and mut-hsp genes were cloned into a plant expression vector for transformation into tobacco plants. These transformations were successful and gave rise to 22 Km' and 18 Km' plants from the WT- and Mut-Hsp constructs respectively. Two plant lines, M5 and M10, transformed with the mut-hsp transgene construct, appeared to have a high level of resistance to the challenging potato X potexvirus, whereas all the other tested plants were susceptible to the challenging virus. It was thus shown that a dysfunctional form of the GLRaV-3 Hsp70h could provide resistance to an unrelated virus in tobacco.
AFRIKAANSE OPSOMMING: Wingerdrolblaar-geassosieerde virus 3 (GLRaV-3) is een van 10 lede van die Closteroviridae wat wingerd kan infekteer. Nege van die virusse is met wingerdrolblaar geassosieer. Die GLRaV-1 en GLRaV-3 is die belangrikste en mees wyd verspreide lede van die rolblaar-geassosieerde Closteroviridae. Lede van die Closteroviridae is uniek in die opsig dat die virusse vir 'n 70 kDa-homoloë hitteresponsproteïen (Hsp70h) kodeer. Die Hsp70 is 'n bewegingsproteïen (MP) wat belangrik is vir die translokasie van die virus deur die plasmodesmata na die naasliggende sel. Breë-spektrum weerstand teen onverwante virusse kan behaal word deur 'n patogeen-afgeleide weerstandstrategie (POR), wat op die uitdrukking van 'n disfunksionele MP wat in plante uitgedruk word, gebaseer is. Die Hsp70hproteïen het twee gebiede. Die N-terminale gebied is In ATPase-gebied en toon hoë homologie met ander ATPase-gebiede van Hsp70h-proteïene van die Closteroviridae, asook die prokariotiese en eukariotiese koninkryke. Gekonserveerde aminosure wat belangrik is vir die posisionering van ATP in die katalitiese domein vir ATP-hidrolise is in die ATPase-gebied gevind. Die C-terminale gebied is variërend en die funksie van die gebied in die Closteroviridae is onbekend. In prokariotiese en eukariotiese Hsp70h-proteïene is die C-terminale gebied belangrik vir proteïenproteïen interaksies. Die nukleotiedvolgorde van die Amerikaanse NY-1-isolaat van GLRaV-3 is al bepaal en POR-strategieë is ook op die kapsiedproteïen, uiteenlopende kapsiedproteïen en die replikasie-proteïen uitgevoer, maar nog nie op 'n disfunksionele vorm van die Hsp70h-geen nie. In hierdie studie is dubbelstring-RNA (dsRNA) van 'n kommersiële wingerd met onbekende virusstatus wat rolblaarsimptome toon, geïsoleer, asook van twee wingerde met 'n bekende virusstatus, een met ligte en een met strawwe simptome. Die GLRaV-3 hsp70h-geen is met hulp van die polimerasekettingreaksie-metode (PKR) vanaf die dsRNA geamplifiseer en die geen se nukleotiedvolgorde is bepaal. Die hsp 70-gene van drie verskillende wingerde het meer as 94% homologie met die NY-1-isolaat getoon. Die gekonserveerde aminosure wat vir ATPase-aktiwiteit belangrik is, was teenwoordig. Die hsp70h-geen van GLRaV-3, wat uit 'n kommersiële wingerd met duidelike rolblaarsimptome in die Stellenbosch-gebied geïsoleer is, is vir verdere navorsing gekies en dit is aan setel-gerigte mutagenese blootgestelom vier mutasies van die geen te bewerkstellig. Die gevolg van hierdie vier mutasies was die verandering van Asn na Asp", Gly na Thr1o, Lys na Glu174 en Asn na Asp197. Die wilde (WT) en veranderde (Mut) vorms van die hsp-gene is in 'n bakteriese uitdrukkingsvektor gekloneer. Uitdrukking van beide die WT- en die Mut-Hspproteïene is behaal, maar die proteïene was in die onoplosbare fraksie geleë. Pogings om die onoplosbare proteïene te isoleer en in 'n aktiewe oplosbare vorm te verkry, was onsuksesvol. Verdere pogings om die proteïene in die oplosbare fraksie van die bakteriese ekspressiesisteem uit te druk, was ook onsuksesvol. As gevolg van die gebrek aan aktiewe proteïen kon biochemiese toetse nie op die ATPaseaktiwiteit van die WT- en Mut-Hsp proteïne gedoen word nie. Die wt- en mut-hsp-gene is ook in In plantekspressievektor gekloneer vir transformasie in tabakplante. Hierdie transformasies was suksesvol en het aanleiding gegee tot 22 kanamisienbestande (Km') en 18 Km' plante vanaf die WT- en Mut-Hspkonstrukte onderskeidelik. Twee plantlyne, M5 en M10, wat met die mut-hsptransgene getransformeer is, het 'n hoë vlak van weerstand teen die infekterende aartappelvirus X getoon in vergelyking met ander plante wat met die virus geïnfekteer is. Daar is dus bewys gelewer dat 'n disfunksionele vorm van die GLRaV-3 Hsp70h weerstand kan bied teen 'n onverwante virus in tabak.

Thesis (PhD (Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2006.
A study was performed to develop a generic pest monitoring system for sampling the main table grape pests in vineyards in the Hex River Valley, Western Cape Province of South Africa. The presence of phytophagous and predatory mites on cover crop plants was also investigated as this may contribute to biological control of the phytophagous mites in vines. Life table studies for Epichoristodes acerbella (Walker), an important phytosanitary pest, were conducted to determine whether or not this pest was sensitive to high temperatures. Information gained from the latter can also be used for breeding purposes in the possible future development of a sterile insect technique (SIT) programme to control this pest. The sampling system consisted of inspecting 20 plots of five vines per plot per one to two hectares. The top fork of each of the five vines per plot was examined for Planococcus ficus (Signoret) to a distance of within 30 cm of the stem, as well as the distal 15 cm of one cane per vine for the presence of P. ficus and damage caused by Phlyctinus callosus Boh. One bunch per vine was examined for insect damage or presence, and one leaf per vine for the presence of leaf infesting arthropods, such as Tetranychus urticae Koch, P. ficus and Frankliniella occidentalis (Pergande). Corrugated cardboard bands, tied around the stem of one vine per plot, were used to monitor activity of P. callosus. Blue sticky traps, at a density of four to five traps per one to two hectares, were used to monitor activity of F. occidentalis. Pheromone traps, at a density of one trap per one to two hectares, were used to monitor activity of P. ficus, E. acerbella and Helicoverpa armigera (Hübner). All the above-mentioned inspections were done at two-weekly intervals, except traps for E. acerbella and H. armigera, which were inspected weekly. In each of the rows in which the sample plots were situated, one leaf of each of the cover crop plant species was examined for the presence of phytophagous mites and their predators. The abundance and distribution of cover crop plants were determined using a co-ordinate sampling system. Cover crop sampling was done at monthly intervals. The current threshold for P. ficus is 2% stem infestation, which is reached when more than 65 males per pheromone trap are recorded. Counting mealybugs on the sticky pads in the pheromone traps is time consuming. However, the number of grid blocks on the sticky pad with males present can be counted. When P. ficus males are found in 27 blocks on the sticky pad, stem inspections should commence. Due to the spatial association between P. ficus bunch and stem infestation, stem infestation could give an indication of where bunch infestation could be expected. The use of blue sticky traps for predicting halo spot damage, caused by F. occidentalis, is not recommended. The presence of thrips on the vine leaves could not give an indication of where to expect bunch damage, since thrips on the leaves and halo spot damage were not spatially associated. A suitable sampling method for F. occidentalis still needs to be developed. The monitoring system described here can only provide information on the infestation status of the vineyard. For E. acerbella, H. armigera and P. callosus, the traps and cardboard bands could be used to identify vineyards where these pests are present and therefore, where phytosanitary problems may arise. The presence of P. callosus under the bands was spatially associated with P. callosus damage and could be used as an indicator of the latter. The presence of drosophilid flies in the bunches could not be used as an indicator of the presence of E. acerbella in the bunches. If 5% bunch damage is used as an economic threshold for E. acerbella and P. callosus, there will be a good chance of not under spraying if control measures are applied at 1% bunch damage. Epichoristodes acerbella favoured more moderate constant temperatures, with constant temperatures of 28°C and above being unfavourable for development. The economic threshold for Tetranychus urticae Koch is six mites per leaf, or if presence-absence sampling is used, 11 to 29% leaf infestation. Three important predatory mites, that kept T. urticae under control, were found in the Hex River Valley, namely Euseius addoensis (Van der Merwe & Ryke), Neoseiulus californicus (McGregor) and an undescribed phytoseiid in the genus Typhlodromus. Various cover crop plants served as hosts for T. urticae and predatory mites. The presence of these plants created suitable conditions for the survival of these mites and may have influenced their presence on the vine leaves. In the case of phytosanitary pests, both field and pack shed inspections can be used to conclude with a 99% degree of certainty that infestation levels in the pack shed will be 10% or less, since similar results for both methods were obtained. However, more than 20 plots will have to be inspected.

Thesis (MScAgric )--Stellenbosch University, 2004.
ENGLISH ABSTRACT: In an attempt to combat some of the pathogens that are associated with trunk diseases and disorders of grapevines, research in this thesis focused on the taxonomy and pathological aspects of Coniellai/Pilidiella, Botryosphaeria and Phomopsis spp. Previously, conidial pigmentation was used to separate Pilidiella from Coniella. Recently, however, the two genera have been regarded as synonymous, with the older name, Coniella, having priority. The most important species in the Coniellai/Pilidiella complex of grapevines is C. diplodiella (Speg.) Petr. & Syd., the causal organism of white rot of grapevines. Previous studies found it difficult to distinguish between C. diplodiella and C. fragariae (Oudem.) B. Sutton, which is known to occur in soil and caused leaf diseases of Fragaria and Eucalyptus. Both these species have previously been reported from South Africa. None of the reports on C. diplodiella could be scientifically substantiated; therefore it is still a quarantine organism. However, this status has been questioned. Based on sequence analyses of the internal transcribed spacer region (ITS 1, ITS 2), 5.8S gene, large subunit (LSU) and elongation factor 1- α gene (EF l- α) from the type species of Pilidiella and Coniella, Coniella was separated from Pilidiella, with the majority of taxa residing in Pilidiella. Pilidiella is characterised by species with hyaline to pale brown conidia (avg. length: width >1.5), with Coniella having dark brown conidia (avg. length: width ≤1.5). Pilidiella diplodiella, previously C. diplodiella, causal organism of white rot of grapevines, was shown to be an older name for C. petrakii. This fungus is present in South Africa and is therefore no longer of quarantine importance. Based on analyses of the histone (H3) gene sequences of isolates in the P. diplodiella species complex, P. diplodiella was separated from a newly described species, P. diplodiopsis. A new species, P. eucalyptorum, is proposed for isolates formerly treated as C. fragariae, associated with leaf spots of Eucalyptus spp. This species clustered basal to Pilidiella, and may represent yet a third genus within this complex. Pilidiella destruens was newly described as anamorph of Schizoparme destruens, which is associated with twig dieback of Eucalyptus spp. in Hawaii. The genus Botryosphaeria Ces. & De Not. are known to be cosmopolitan, with broad host ranges and geographical distributions. Several saprotrophic species have been reported from grapevines, while others are severe pathogens of this host. These species include B. dothidea (Moug.: Fr.) Ces. & De Not., B. parva Pennycook & Samuels, B. obtusa (Schwein.) Shoemaker, B. stevensii Shoemaker, B. lutea A.J.L. Phillips and B. ribis Grossenb. & Duggar. Species reported from South Africa as grapevine pathogens are B. obtusa, B. dothidea, B. ribis and B. vitis (Schulzer) Sacco. In the present study, morphological, DNA sequence data (ITS 1, 5.8S, ITS 2 and EFI-α) and pathological data were used to distinguish 11 Botryosphaeria spp. associated with grapevines from South Africa and other parts of the world. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina and a Diplodia sp. were confirmed from grapevines in South Africa, while Diplodia porosum, Fusicoccum viticlavatum and F. vitifusiforme were described as new species. Although isolates of B. dothidea and B. stevensii were confirmed from grapevines in Portugal, neither of these species, nor B. ribis, were isolated in this study. All grapevine isolates from Portugal, formerly presumed to be B. rib is, are identified as B. parva based on EF1-α sequence data. Artificial inoculations on grapevine shoots showed that B. australis, B. parva, B. ribis and B. stevensii are more virulent than the other species studied. The Diplodia sp. collected from grapevine canes was identified as morphologically similar, but phylogenetically distinct from D. sarmentorum, while D. sarmentorum was confirmed as anamorph of Otthia spiraeae, the type species of the genus Otthia (Botryosphaeriaceae). A culture identified as O. spiraeae clustered within Botryosphaeria, and is thus regarded as a probable synonym. These findings confirm earlier suggestions that the generic concept of Botryosphaeria should be expanded to include genera with septate ascospores and Diplodia anamorphs. The genus Phomopsis (Sacc.) Bubak contains many species that are plant pathogenic or saprotrophic. Ten species are known from grapevines. However, only two have been confirmed as being pathogenic, namely P. viticola (Sacc.) Sacc., causal organism of Phomopsis cane and leaf spot and P. vitimegaspora Kuo & Leu (teleomorph Diaporthe kyushuensis Kajitani & Kanem.), causal organism of swelling arm disease of grapevines. P. amygdali (Delacr.) 1.1. Tuset & M.T. Portilla, a known pathogen from Prunus sp., was shown to be a possible pathogen of grapevines in a previous study. D. perjuncta Niessl. causes bleaching of dormant canes only and is therefore of little importance as a grapevine pathogen. Recently a number of Phomopsis isolates were obtained from grapevines in the Western Cape province of South Africa. Isolations were made from Phomopsis-like symptoms, pruning wounds and asymptomatic nursery plants. These isolates showed great variation in morphology and cultural characteristics. Earlier taxonomic treatments of Phomopsis, based species identification on host specificity, cultural characteristics and morphology. Recent studies have indicated that these characteristics can no longer be used to distinguish species of Phomopsis due to wide host ranges and morphological plasticity of some species. The use of anamorph/teleomorph relationships in species identification is also untenable, since Diaporthe teleomorphs have only been described for approximately 20% of the known Phomopsis species. In this study morphological data, DNA sequences (ITS-I, 5.8S, ITS-2) and pathogenicity data were combined to distinguish Phomopsis spp. from grapevines. Fifteen species of Phomopsis were delineated by phylogenetic analysis of ITS sequence data. Diaporthe helianthi, a sunflower pathogen, was reported from grapevines for the first time, with a further six, unknown species also distinguished. Three different clades contained isolates previously identified as D. perjuncta. Based on type studies, it appeared that the name D. viticola was available for collections from Portugal and Germany, a new species, D. australafricana, was proposed for South African and Australian isolates, formerly treated as D. perjuncta or D. viticola. An epitype specimen and culture were designated for D. perjuncta. This species was distinguished from D. viticola and D. australafricana based on morphology and DNA phylogeny. Artificial inoculations of green grapevine shoots indicated that, of the species tested, P. amygdali, a known pathogen of peaches in the USA, and P. viticola were the most virulent.
AFRIKAANSE OPSOMMING: In 'n poging om sommige patogene geassosieer met stamsiektes en syndrome, te beveg, het die navorsing in die tesis gefokus op die taksonomie en patologiese aspekte van ConiellaiPilidiella, Botryosphaeria en Phomopsis spp Voorheen is konidium pigmentasie gebruik om Pilidiella (hialien tot ligbruin konidia) van Coniella (donkerbruin konidia) te skei. Onlangs is hierdie twee genera egter as sinoniem beskou met die ouer naam, Coniella, wat voorkeur gekry het. Die belangrikste spesies in die ConiellaiPilidiella kompleks van wingerd is C. diplodiella (Speg.) Petr. & Syd., die veroorsakende organisme van witvrot van wingerd. Vorige studies het dit moeilik gevind om te onderskei tussen C. diplodiella en C. fragariae (Oudem.) B. Sutton, wat bekend is dat dit in grond voorkom en ook blaarsiektes van Fragaria en Eucalyptus veroorsaak. Beide hierdie spesies is tevore in Suid-Afrika aangemeld. Geen van die aanmeldings van C. diplodiella is egter wetenskaplik bewys nie en daarom is dit steeds 'n kwarantyn organisme. Hierdie kwarantyn status is egter bevraagteken. Op grond van DNS volgordes van die interne getranskribeerde spasieerder area ("ITS 1", "ITS2"), die 5.8S rRNS geen, die groot ribosomale subeenheid ("LSU") en die verlengingsfaktor 1-α geen ("EF-lα") van die tipe spesies van Pilidiella en Coniella, is Coniella van Pilidiella geskei, met die meerderheid van die taxa wat binne Pilidiella resorteer. Pilidiella word gekarakteriseer deur spesies met hialien tot ligbruin konidia (gem. lengte: breedte > 1.5), in teenstelling met die donkerbruin konidia van Coniella (gem. lengte: breedte ≤ 1.5). Daar is verder bewys dat Pilidiella diplodiella, voorheen C. diplodiella, veroorsakende organisme van witvrot van wingerd, die ouer naam van C. petrakii is. Hierdie swam is teenwoordig in Suid-Afrika en P. diplodiella is dus nie meer van kwarantyn belang nie. Op grond van analises van die histoon (H3) volgordes van spesies in die P. diplodiella spesies kompleks, is P. diplodiella geskei van 'n nuut beskryfde spesie, P. diplodiopsis. 'n Nuwe spesie, P. eucalyptorum, is ook voorgestel vir isolate voorheen beskou as C. fragariae, geassosieer met blaarvlek van Eucalyptus spp. Hierdie spesie het basaal van Pilidiella gegroepeer en mag moontlik nog 'n derde genus binne hierdie kompleks verteenwoordig. Pilidiella destruens is nuut as anamorf van Schizoparme destruens beskryf, wat geassosieer word met loot terugsterwing van Eucalyptus spp. in Hawaii. Die genus Botryosphaeria Ces. & De Not. is bekend as kosmopolitaans met 'n wye gasheerreeks en geografiese verspreiding. Verskeie saprofitiese spesies is aangemeld vanaf wingerd, terwyl ander ernstige patogene van hierdie gasheer is. Laasgenoemde spesies sluit in B. dothidea (Moug.: Fr.) Ces. & De Not., B. parva Pennycook & Samuels, B. obtusa (Schwein.) Shoemaker, B. stevensii Shoemaker, B. lutea A.1.L. Phillips en B. ribis Grossenb. & Duggar. Spesies aangemeld in Suid-Afrika as wingerdpatogene, is B. obtusa, B. dothidea, B. ribis en B. vitis (Schulzer) Sacco In hierdie studie is morfologiese, DNS volgorde data ("ITSl", "ITS2", 5.8S en "EF-Iα") en plantpatologiese data gebruik om II Botryosphaeria spesies, geassosieer met wingerde in Suid-Afrika en verskeie ander werelddele, te onderskei. Botryosphaeria australis, B. lutea, B. obtusa, B. parva, B. rhodina en 'n Diplodia sp. is bevestig van wingerde in Suid-Afrika, terwyl Diplodia porosum, Fusicoccum viticlavatum en F. vitifusiforme as nuwe spesies beskryf is. AIhoewel isolate van B. dothidea en B. stevensii bevestig is van wingerde in Portugal, is geen van hierdie spesies en ook nie B. ribis geïsoleer nie. AIle isolate vanaf wingerd in Portugal, voorheen beskou as B. rib is, is as B. parva op grond van hul "EF-lα" volgordes geïdentifiseer. Uit kunsmatige isolasies gemaak op wingerdlote is die gevolgtrekking gemaak dat B. australis, B. parva, B. ribis en B. stevensii meer virulent is as die ander spesies wat bestudeer is. Die Diplodia sp. versamel vanaf wingerdlote is geïdentifiseer as morfologies eenders, maar filogeneties verskillend van D. sarmentorum, terwyl D. sarmentorum bevestig is as die anamorf van Otthia spiraeae, die tipe spesie van die genus Otthia (Botryosphaeriaceae). 'n Kultuur wat as 0. spiraeae geïdentifiseer is, het binne Botryosphaeria gegroepeer, en word dus as 'n moontlike sinoniem beskou. Hierdie bevindinge bevestig vroeëre voorstelle dat die generiese konsep van Botryosphaeria uitgebrei behoort te word om genera met gesepteerde askospore en Diplodia anamorwe in te sluit. Die genus Phomopsis (Sacc.) Bubak bevat verskeie spesies wat as of plantpatogenies, of saprofities, beskryf is. Tien spesies is bekend op wingerd. Slegs twee is as patogenies bevestig, naamlik P. viticola (Sacc.) Sacc., veroorsakende organisme van loot-en-blaarvlek ("streepvlek") en P. vitimegaspora Kuo & Leu (teleomorf Diaporthe kyushuensis Kajitani & Kanem.), veroorsakende organisme van geswelde arm van wingerd. In 'n vroeëre studie is bevind dat P. amygdali (Delacr.) 1.1. Tuset & M.T. Portilla, 'n bekende patogeen van Prunus sp., moontlik ook 'n patogeen van wingerd mag wees. D. perjuncta Niessl. veroorsaak egter net verbleiking van dormante lote en is dus van min belang as 'n wingerd patogeen. Gedurende die afgelope twee jaar is verskeie Phomopsis isolate van wingerde in die Wes-Kaap provinsie van Suid-Afrika verkry. Isolasies is gemaak van Phomopsis-agtige simptome, snoeiwonde en asimptomatiese kwekeryplante. Die isolate verkry uit hierdie materiaal het groot variasie ten opsigte van morfologie en kultuureienskappe getoon. Vroeëre taksonomiese verhandelings van Phomopsis het spesies-identifikasie op gasheerspesifisiteit, kultuureienskappe en morfologie gebasseer. Onlangse studies het egter getoon dat, weens wye gasheerreekse en morfologiese plastisiteit van somnuge spesies, hierdie eienskappe me meer gebruik kan word om Phomopsis spesies te identifiseer nie. Die gebruik van anamorflteleomorf verwantskappe in die identifikasie van Phomopsis spesies ook onbruikbaar omdat Diaporthe teleomorwe vir slegs ongeveer 20% van die bekende Phomopsis spesies beskryf is. Die huidige studie het dus morfologiese data, DNS volgordes ("ITS 1", 5.8S, "ITS2") en patogenisiteitsdata gekombineer ten einde Phomopsis spp. vanaf wingerd te identifiseer. Vyftien Phomopsis spesies is deur die filogenetiese analise van die interne getranskribeerde spasieerder area ("ITS") volgordes geskei. Diaporthe helianthi, 'n bekende patogeen van sonneblomme, is vir die eerste maal op wingerd aangeteken, terwyl 'n verdere ses, tans onbekende spesies van Phomopsis ook geidentifiseer is. Drie verskillende groepe het isolate bevat wat voorheen as D. perjuncta geidentifiseer is. Gebasseer op studies van tipes, het dit voorgekom dat die naam D. viticola beskikbaar is vir isolate uit Portugal en Duitsland. 'n Nuwe spesie, D. australafricana, is voorgestel vir Suid-Afrikaanse en Australiese isolate wat voorheen behandel is as D. perjuncta of D. viticola. 'n Epitipe monster en kultuur is vir D. perjuncta benoem. Hierdie spesie is van D. viticola en D. australafricana onderskei op grond van morfologie en DNS filogenie. Kunsmatige inokulasies van groen wingerdlote het getoon dat P. amygdali, bekende perske patogeen, en P. viticola die mees virulent was.

Includes bibliographical references (leaves 217-230). Details the biology and life history of the Quandong moth and investigates management strategies that would enable growers to manage the pest in an economically and environmentally sustainable program.

Thesis (MSc (Genetics))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: South Africa is regarded as one of the top wine producing countries in the world. One of the threats to the sustainability of the wine industry is viral diseases of which Grapevine leafroll-associated virus 3 (GLRaV-3) and Grapevine virus A (GVA) are considered to be the most important and wide spread. Scion material is regularly tested for viruses; however scion material is often grafted onto rootstocks that have questionable phytosanitary status. Virus detection in rootstocks is challenging due to low and varying titres, but is imperative as a viral control mechanism. An additional viral control mechanism is the use of transgenic grapevine material which offers resistance to grapevine infection. The objective of this project was to establish a detection system using real time PCR (qPCR) techniques, to accurately and routinely detect GLRaV-3 and GVA in rootstock propagation material. qPCR would furthermore be used to perform molecular characterisation of transgenic plants containing a GLRaV-3 antiviral ΔHSP-Mut construct. A severely infected vineyard (Nietvoorbij farm) in the Stellenbosch area was screened throughout the grapevine growing season to investigate virus prevalence throughout the season and to determine the optimal time for sensitive virus detection. A large scale screening of nursery propagation material for GLRaV-3 infection was also conducted. The qRT-PCR results were compared to DAS-ELISA results to compare the efficacy and sensitivity of the two techniques. For the severely infected vineyard, the ability to detect GLRaV-3 increased as the season progressed towards winter. qRT-PCR was more sensitive and accurate in detecting GLRaV-3 than DASELISA, as the latter technique delivered numerous false positive results later in the season. The best time to screen for GLRaV-3 in the Western Cape region was from the end of July to September. For the nursery screenings, our qRT-PCR results were compared to the results of the DAS-ELISA performed by the specific nurseries. No GLRaV-3 infection was detected in the specific samples received from the two different nurseries. The results for all the samples correlated between the two techniques. This confirms that the propagation material of these nurseries has a healthy phytosanitary status with regards to GLRaV-3. However, the detection of GVA in the severely infected vineyard yielded inconsistent results. Detection ability fluctuated throughout the season and no specific trend in seasonal variation and virus titre fluctuation could be established. The highest percentage of GVA infected samples were detected during September, April and the end of July. Previously published universal primers were used for the detection of GVA, but further investigation indicated that they might not be suitable for sensitive detection of specific GVA variants present in South Africa. Vitis vinifera was transformed with a GLRaV-3 antiviral construct, ΔHSP-Mut. SYBR Green Real time PCR (qPCR) and qRT-PCR were utilised as alternative methods for molecular characterisation of transgenic plants. The qPCR and Southern blot results correlated for 76.5% of the samples. This illustrated the ability of qPCR to accurately estimate transgene copy numbers. Various samples were identified during qRT-PCR amplification that exhibited high mRNA expression levels of the transgene. These samples are ideal for further viral resistance studies. This study illustrated that the versatility of real time PCR renders it a valuable tool for accurate virus detection as well as copy number determination.
AFRIKAANSE OPSOMMING: Suid Afrika word geag as een van die top wyn produserende lande ter wereld. Die volhoubaarheid van die wynbedryf word onder andere bedreig deur virus-infeksies. Grapevine leafroll associated virus 3 (GLRaV-3) en Grapevine virus A (GVA) is van die mees belangrike virusse wat siektes veroorsaak in Suid-Afrikaanse wingerde. Wingerd bo-stok materiaal word gereeld getoets vir hierdie virusse, maar hierdie materiaal word meestal geënt op onderstokmateriaal waarvan die virus status onbekend is. Virus opsporing in onderstokke word egter gekompliseer deur baie lae en variërende virus konsentrasies, maar opsporing in voortplantingsmateriaal is ‘n noodsaaklike beheermeganisme vir virus-infeksie. Die doel van die projek was om ‘n opsporingsisteem te ontwikkel via kwantitatiewe PCR (qPCR) tegnieke vir akkurate en gereelde toetsing van GLRaV-3 en GVA in onderstokmateriaal. qPCR sal ook verder gebruik word vir molekulêre karakterisering van transgeniese plante wat ‘n GLRaV-3 antivirale ΔHSP-Mut konstruk bevat. ‘n Hoogs geïnfekteerde wingerd was regdeur die seisoen getoets om seisoenale fluktuasies in viruskonsentrasie te ondersoek en om die optimale tydstip vir sensitiewe virus opsporing te bepaal. ‘n Grootskaalse toetsing van kwekery voortplantingsmateriaal vir GLRaV-3 infeksie was ook uitgevoer. Die qRT-PCR resultate is met die DAS-ELISA resultate vergelyk om die effektiwiteit en sensitiwiteit van die twee tegnieke te vergelyk. Vir die hoogs geïnfekteerde wingerd het die GLRaV-3 opsporing toegeneem met die verloop van die seisoen tot en met winter. qRT-PCR was meer sensitief en akkuraat as DAS-ELISA in die opsporing van GLRaV-3, weens verskeie vals positiewe resultate wat later in die seisoen deur die laasgenoemde tegniek verkry is. Die beste tyd om vir GLRaV-3 te toets is vanaf einde Julie tot September. Tydens die kwekery toetsings was qRT-PCR resultate met die DAS-ELISA resultate van die spesifieke kwekerye vergelyk. Geen GLRaV-3 infeksie was waargeneem in die spesifieke monsters wat vanaf die kwekerye ontvang is nie. Die resultate van die twee tegnieke het ooreengestem vir al die monsters wat v getoets is. Dit het bevestig dat die voortplantingsmateriaal van hierdie kwekerye gesonde fitosanitêre status met betrekking tot GLRaV-3 gehad het. Die opsporing van GVA in die geïnfekteerde wingerd het egter wisselvallige resultate gelewer. Opsporing van die virus het ook regdeur die seisoen gefluktueer en geen spesifieke neiging in seisoenale opsporingsvermoë kon gemaak word nie. Die hoogste persentasie GVA geïnfekteerde monsters was waargeneem tydens September, April en die einde van Julie. Voorheen gepubliseerde universele inleiers was gebruik vir die opsporing van GVA, maar verdere ondersoeke het getoon dat hierdie inleiers nie noodwendig geskik is vir sensitiewe opsporing van GVA variante wat teenwoordig is in Suid-Afrika nie. Vitis vinifera was getransformeer met ‘n GLRaV-3 antivirale konstruct, ΔHSP-Mut. SYBR Green Real time PCR (qPCR) en qRT-PCR was ingespan as alternatiewe metodes vir molekulêre karaterisering van transgeniese plante. Die qPCR en Southern-klad resultate het ooreengestem vir 76.5% van die monsters. Dit illustreer die vermoë van qPCR om akkurate kopie-getalle van transgene te bepaal. Verskeie plante is geïdentifiseer tydens qRT-PCR amplifisering wat hoë vlakke van transgeen mRNA uitdrukking getoon het. Hierdie monsters is ideaal vir verdere virus weerstandbiedendheids studies. Hierdie studie het die veelsydigheid van real time PCR bewys en getoon dat dit ‘n kosbare tegniek is vir akkurate virus opsporing sowel as kopie-getal bepaling.

Thesis (MScAgric)--University of Stellenbosch, 2006.
ENGLISH ABSTRACT: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, and Botryosphaeria spp. are important trunk disease pathogens that cause premature decline and dieback of grapevine. Previous research has focused primarily on wine grapes and the incidence and symptomatology of these pathogens on table grapes were largely unknown. A survey was therefore conducted to determine the status and distribution of these pathogens and associated symptoms in climatically diverse table grape growing regions. Fifteen farms were identified in the winter rainfall (De Doorns, Paarl and Trawal) and summer rainfall (Upington and Groblersdal) areas. Samples were taken in July and August 2004 from Dan-ben-Hannah vineyards that were 8 years and older. Distal ends of arms were removed from 20 randomly selected plants in each vineyard. These sections were dissected and isolations were made from each of the various symptom types observed: brown or black vascular streaking, brown internal necrosis, wedge-shaped necrosis, watery necrosis, esca-like brown and yellow soft wood rot, as well as asymptomatic wood. Fungal isolates were identified using molecular and morphological techniques. Pa. chlamydospora was most frequently isolated (46.0%), followed by Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa (3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B. dothidea and an undescribed Diplodia sp. (0.2% each), while E. lata was not found. Most of these pathogens were isolated from a variety of symptom types, indicating that disease diagnosis can not be based on symptomatology alone. Pa. chlamydospora was isolated from all areas sampled, although most frequently from the winter rainfall region. Pm. aleophilum was found predominantly in Paarl, while P. viticola only occurred in this area. Although B. obtusa was not isolated from samples taken in De Doorns and Groblersdal, it was the most commonly isolated Botryosphaeria sp., being isolated from Upington, Paarl and Trawal. B. rhodina occurred only in Groblersdal and B. parva in Paarl, Trawal and Groblersdal, while B. australis was isolated from Paarl only. The rest of the isolates (33%) consisted of sterile cultures, Exochalara, Cephalosporium, Wangiella, Scytalidium, Penicillium spp. and two unidentified basidiomycetes, which were isolated from five samples with yellow esca-like symptoms from the Paarl area. These findings clearly illustrate that grapevine trunk diseases are caused by a complex of fungal pathogens, which has serious implications for disease diagnosis and management. Protection of wounds against infection by any of these trunk disease pathogens is the most efficient and cost-effective means to prevent grapevine trunk diseases. However, previous research on the effectiveness of chemical pruning wound protectants has mostly focused on the control of Eutypa dieback only. Fungicide sensitivity studies have been conducted for Pa. chlamydospora, P. viticola and Eutypa lata, but no such studies have been conducted for the pathogenic Botryosphaeria species from grapevine in South Africa. Ten fungicides were therefore tested in vitro for their efficacy on mycelial inhibition of the four most common and/or pathogenic Botryosphaeria species in South Africa, B. australis, B. obtusa, B. parva and B. rhodina. Iprodione, pyrimethanil, copper ammonium acetate, kresoxim-methyl and boscalid were ineffective in inhibiting the mycelial growth at the highest concentration tested (5 μg/ml; 20 μg/ml for copper ammonium acetate). Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole were the most effective fungicides with EC50 values for the different species ranging from 0.36-0.55, 0.07-0.17, 0.07-1.15 and 0.04-0.36 μg/ml, respectively. These fungicides, except prochloraz manganese chloride, are registered on grapes in South Africa and were also reported to be effective against Pa. chlamydospora, P. viticola and E. lata. Results from bioassays on 1-year-old Chenin Blanc grapevine shoots indicated that benomyl, tebuconazole and prochloraz manganese chloride were most effective in limiting lesion length in pruning wounds that were inoculated with the Botryosphaeria spp after fungicide treatment. The bioassay findings were, however, inconclusive due to low and varied re-isolation data of the inoculated lesions. Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole can nonetheless be identified as fungicides to be evaluated as pruning wound protectants in additional bioassays and vineyard trials against Botryosphaeria spp. as well as the other grapevine trunk disease pathogens.
AFRIKAANSE OPSOMMING: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, en Botryosphaeria spesies is die mees belangrikste stamsiekte patogene wat agteruitgang en vroeë terugsterwing van wingerd veroorsaak. Voorafgaande navorsing het hoofsaaklik gefokus op wyndruiwe en die voorkoms en simptomatologie van hierdie patogene op tafeldruiwe is dus grootliks onbekend. ‘n Opname is gevolglik gedoen in verskillende klimaaatsareas waar tafeldruiwe verbou word om die voorkoms en verspreiding, asook die simptome geassosieer met hierdie patogene, te bepaal. Vyftien plase is geïdentifiseer in die winter- (De Doorns, Paarl en Trawal) en somer-reënval (Upington en Groblersdal) streke. Wingerde (8 jaar en ouer) met die kultivar Dan-ben-Hannah is gekies vir opname en monsters is gedurende Julie en Augustus 2004 geneem. Die distale deel van ‘n arm is verwyder vanaf 20 lukraak gekose plante in elke wingerd. Hierdie dele is ontleed en isolasies is gemaak vanuit elke simptoomtipe wat beskryf is, naamlik bruin en swart vaskulêre verkleuring, bruin interne nekrose, wig-vormige nekrose, waterige nekrose, esca-geassosieerde bruin en geel sagte houtverrotting en asimptomatiese hout. Identifikasie van die swamagtige isolate is gedoen op grond van morfologiese eienskappe en molekulêre tegnieke. Pa. chlamydospora is die meeste geïsoleer (46.0%), gevolg deur Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa (3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B. dothidea en ‘n onbeskryfde Diplodia sp. (0.2% elk), terwyl E. lata nie geïsoleer is nie. Hierdie patogene is elk geïsoleer vanuit ‘n verskeidenheid simptoomtipes, wat daarop dui dat siektediagnose nie alleenlik op simptomatologie gebaseer kan word nie. Pa. chlamydospora is geïsoleer vanuit al die gebiede, alhoewel die patogeen opmerklik meer voorgekom het in die winter-reënval area. Pm. aleophilum het hoofsaaklik voorgekom in Paarl, terwyl P. viticola slegs in hierdie area voorgekom het. Alhoewel B. obtusa nie voorgekom het in die De Doorns en Groblersdal areas nie, was dit die mees algemeen geïsoleerde Botryosphaeria sp. en het in Upington, Paarl en Trawal voorgekom. B. rhodina het slegs in Groblersdal voorgekom, B. parva in Paarl, Groblersdal en Trawal en B. australis het slegs in Paarl voorgekom. Die res van die isolate (33%) het bestaan uit steriele kulture, Exochalara, Cephalosporium, Wangiella, Scytalidium, en Penicillium spesies asook twee onbekende basidiomycete isolate, geïsoleer vanuit vyf monsters met geel eska-geassosieerde simptome vanuit die Paarl area. Hierdie resultate illustreer dus die feit dat wingerdstamsiektes deur ‘n kompleks van swampatogene veroorsaak word, wat belangrike implikasies het vir die bestuur en diagnose van hierdie siektes. Wondbeskerming teen infeksie van enige van hierdie stamsiekte patogene is die mees doeltreffende en koste-effektiewe manier om wingerdstamsiektes te voorkom. Vorige navorsing aangaande die effektiwiteit van chemiese wondbeskermingsmiddels het egter slegs gefokus op die beheer van Eutypa terugsterwing. In vitro swamdoder sensitiwiteitstoetse is gedoen vir Pa. chlamydospora, P. viticola en Eutypa lata, maar geen studies is al gedoen ten opsigte van die patogeniese Botryosphaeria spesies op wingerd in Suid-Afrika nie. Tien swamdoders is dus getoets vir inhibisie van in vitro miseliumgroei van die vier mees algemene en/of patogeniese Botryosphaeria spesies wat in Suid-Afrika voorkom, naamlik B. australis, B. obtusa, B. parva en B. rhodina. Iprodione, pyrimethanil, koper ammonium asetaat, kresoxim-metiel en boscalid was oneffektief by die hoogste konsentrasies getoets (5 μg/ml; 20 μg/ml vir koper ammonium asetaat). Benomyl, tebuconasool, prochloraz mangaan chloried en flusilasool was die mees effektiewe swamdoders met EC50 waardes tussen 0.36-0.55, 0.07-0.17, 0.07-1.15 en 0.04-0.36 μg/ml, onderskeidelik vir die verskillende spesies. Hierdie fungisiedes, behalwe prochloraz mangaan chloried, is geregistreer op druiwe in Suid-Afrika en is ook effektief gevind teenoor Pa. chlamydospora, P. viticola en E. lata. Resultate van biotoetse op 1-jaar-oue Chenin Blanc wingerd lote het getoon dat benomyl, tebuconasool en prochloraz mangaan chloried die effektiefste was om die lengte van letsels in snoeiwonde, geinokuleer met Botryosphaeria spesies na die aanwending van swamdoder behandelings, te verminder. Die bevindinge was egter onbeslis as gevolg van die lae en variërende her-isolerings data. Benomyl, tebuconasool, prochloraz mangaan chloried en flusilasool kan egter geïdentifiseer word as swamdoders wat verder geevalueer kan word as snoeiwond beskermingsmiddels teen Botryosphaeria spesies asook ander wingerd stamsiekte patogene in verdere biotoetse en wingerdproewe.

The detection by serology of nematode-transmitted polyhedral viruses (nepoviruses) in grapevines is often unreliable. Nepoviruses were detected by enzyme-linked immunosorbent assay (ELISA) in tissue-cultured and field-grown grapevines. Nepovirus detection in in vitro plants (plantlets) was affected by virus distribution and growth room temperature. The reliability of virus detection in field-grown grapevines was improved when modified grinding buffers were used. Arabis mosaic virus (AMV) was detected by ELISA, for the first time, in in vitro grapevines initiated from field-and screenhouse-grown plants throughout the summer. The virus was not reliably and repeatedly detected in in vitro plantlets grown at 25°C. AMV and grapevine fanleaf virus (GFLV) distribution was not uniform throughout the plantlets. This distribution was affected by the culture room temperature. The best plant parts to sample for virus detection came from the zones of rapidly proliferating shoots. The viruses were sometimes not detected in samples taken from other tissues. Growth room temperature had an important effect on virus detection in plantlets. The highest virus titres were found in plants growing at 15°C. Temperature increases in 5°C steps to 30°C reduced virus titre. AMV became undetectable in nearly all plantlets growing at 30°C for as little as 30 days. Growth at 30°C reduced ELISA absorbance values by 76% after 8 days and after 21 days the values were at 4% of pre-treatment levels. The virus titre dropped below detectable levels in most plantlets. AMV could not be detected in plantlets or rooted explants after being placed in a 30°C treatment for 2 months. Tomato ringspot virus was detected by ELISA, for the first time, in in vitro grapevine plants. The virus was repeatedly detected in in vitro plants growing at 20°C. Under the typical summer conditions experienced at Sidney, B.C., modifying the standard ELISA grinding buffer (0.01 M phosphate buffered saline, pH 7.4, 0.05% Tween-20, 0.2% ovalbumin, 2% polyvinylpyrrolidone) was essential for reliable detection of AMV or GFLV. AMV was reliably detected by ELISA in foliar samples from field or screenhouse plants throughout the summer when the grinding buffer was modified by increasing the pH to at least 8.2 and adding 1% nicotine or 0.15 M phosphate buffered saline. The most reliable results with GFLV were obtained with the nicotine enhanced buffers. In comparison, because of the increased workload associated with growing plants in vitro and the unreliable detection of viruses in these plants, it remained preferable to detect nepoviruses in field plants by ELISA.
Land and Food Systems, Faculty of
Graduate

Thesis (MScAgric)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: The evaluation of fungicide efficacy in commercial vineyards can be influenced by the sporadic occurrence of Botrytis cinerea at various positions on vines, differences in bunch structure during bunch development and the phenomenon that symptom expression in shoots and bunches is governed by the resistance reaction of the various shoot and bunch parts. It has been postulated that, following air and water dispersal, infection by solitary conidia should playa prominent role in the epidemiology of B. cinerea on grapevine. The aim of this study was to determine (i) infection and (ii) fungicide efficacy at specific sites on shoots of vinelets and bunches (table grape cultivar Dauphine and the wine grape cultivar Merlot) inoculated with dry, airborne conidia of B. cinerea. Vinelets, prepared from cuttings, and bunches obtained from the vineyards at full bloom, pea size, bunch closure, véraison and harvest stages, were sprayed in a spray chamber at the recommended dosages with iprodione, pyrimethanil, cyprodinil/fludioxonil and fenhexamid or were left unsprayed. After 24 h the vinelets or bunches were dusted with dry conidia of Botrytis cinerea in a settling tower and incubated for 24 h at a high relative humidity (±93%). Following incubation, both the vinelets or bunches were divided into three groups. Vinelets and bunches of the one group were surface-sterilised, the others were left unsterile. Vinelets and bunches of one unsterile group were placed in dry chambers, kept for 14 days at 22°C with a 12 h photoperiod daily and monitored for symptom expression and the development of B. cinerea. Vinelets and bunches of the sterile group, and from one unsterile group were used for isolation. From each of these vinelets leaf blades, leaf petioles, shoots and inflorescences were removed. Sites used for isolation in bunch parts were rachises, laterals and pedicels, and sites on berries were the pedicel-end, cheek and style-end. The different parts and segments were placed in Petri dishes on Kerssies' B. cinerea selective medium, or on water agar medium supplemented with paraquat and incubated for 14 days at 22°C with a 12 h photoperiod daily. Infection and fungicide efficacy was determined by observing intact vinelets and bunches for symptom expression, and by estimating the amount of B. cinerea at the various sites on the vinelets and bunches with isolation studies. No symptoms of B. cinerea decay developed on sprayed and unsprayed vinelets that were kept in dry chambers during the 2 wk observation period. The isolation and incubation studies showed that the different fungicides were highly and nearly equally efficient in reducing superficial B. cinerea inoculum and latent infection. .In the case of leaf blades, which showed a high amount of B. cinerea on unsprayed vinelets under the two sterility regimes, decay was significantly reduced by each fungicide on both cultivars. This was not the case for the other parts, which yielded B. cinerea at low incidences under the two sterility regimes. The study with bunches showed that dry, airborne conidia, and the fungicide sprays, penetrated loose and tight clustered bunches from bloom to harvest and evenly landed on the various bunch parts. At full bloom, the amount of B. cinerea in unsprayed bunches was high on the laterals and pedicels, but low on the embryos. Unsprayed intact bunches at full bloom were highly susceptible to B. cinerea and developed symptoms of grey mould. The fungicides inhibited symptom expression at full bloom, but could not prevent infection. Unsprayed bunches inoculated at the other stages remained asymptomatic. The amount of B. cinerea was generally high in the rachises and laterals at pea size and bunch closure stages, and in the pedicel end of berries at harvest. Infection was constantly low in the berry cheek. The fungicides had a differential effect on infection at the various sites. In the case of rachises, the amount of B. cinerea was at each growth stage drastically reduced by each fungicide. In laterals, it was effectively reduced at pea size and bunch closure. However, at these two sites, significant differences were found between the fungicides in efficacy at stages when the amount of B. cinerea was high. This study showed that if these fungicides are applied properly to vine in commercial vineyards between budding and prebloom, during flowering, and at bunch closure, they should effectively prevent infection and symptom expression and thus the development of B. cinerea epiphytotics.
AFRIKAANSE OPSOMMING: INFEKSIE DEUR DROË, LUGGEDRAAGDE BOTRYTIS CINEREA KONIDIA EN DIE EFFEK VAN FUNGISlEDE OP VERSKILLENDE SETELS BINNE WINGERDTROSSE EN OP LOTE: Evaluering van fungisieddoeltreffendheid in kommersiële wingerde word beïnvloed deur die sporadiese voorkoms van Botrytis cinerea op verskeie posisies van wingerddele, verskille in trosstruktuur tydens trosontwikkeling, en die feit dat simptoomuitdrukking in lote en trosse deur die weerstandsaksie van die verskillende morfologiese dele van lote en trosse beheer word. In die natuur speel infeksie deur enkel konidia 'n prominente rol in die epidemiologie van B. cinerea van wingerd. Die doel van hierdie studie was om (i) infeksie en (ii) die effek van fungisiede op verskillende posisies op lote en trosse (tafeldruif kultivar Dauphine, wyndruif kultivar Merlot), wat met droë, luggedraagde konidia van B. cinerea geïnokuleer is, te bepaal. Lote, verkry vanaf steggies, en trosse versamel vanuit die wingerde tydens blom-, ertjiekorrel-, trostoemaak-, deurslaan- en oesstadium, is teen aanbevole dosisse met iprodione, pyrimethanil, cyprodinillfludioxonil of fenhexamid in 'n spuitkas bespuit, of is onbehandeld gelaat. Na 24 h is die lote en trosse met droë konidia van B. cinerea in 'n inokulasietoring geïnokuleer en daarna vir 24 h onder hoë humiditeit [±93% RH] geïnkubeer. Na inkubasie is die lote en trosse in drie groepe verdeel. Die een groep lote en trosse is oppervlakkig gesteriliseer om die patogeen op die oppervlakte te elimineer, en die ander twee groepe is onbehandeld gelaat. Die lote en trosse van een nie-steriele groep is vir 14 dae in droë voghokke by 22°C met 'n 12 uur daaglikse fotoperiode geplaas, en daagliks vir siekteuitdrukking en die ontwikkeling van B. cinerea gemonitor. Lote en trosse van die ander twee groepe is vir isolasiestudies gebruik. Vanaf elke loot is blaarskywe, blaarstele, internodes en ongeopende blomtrossies verwyder. Vanaftrosse is ragisse, laterale en korreisteie verwyder, en vanaf korrels is skilsegmente aangrensend aan die korrelsteel, die stempel-end, en die wang verwyder. Die dele en segmente is op B. cinerea selektiewe medium, en op paraquat medium in Petri bakkies geplaas en vir 14 dae by 22°C met 'n 12 uur daaglikse fotoperiode geïnkubeer. Infeksie en die fungisiedeffek is bepaal deur die intakte lote en trosse vir siekte- uitdrukking te monitor, en deur die hoeveelheid B. cinerea op verskeie posisies op lote en trosse te bepaal. Geen simptome het op enige posisie op bespuite en onbespuite lote, wat in droë hokke gehou is, ontwikkel nie. Die isolasie- en inkubasiestudies het getoon dat die verskillende fungisiede hoogs effektief op lote was, en inokulumvlakke van die patogeen doeltreffend verlaag het. In die geval van blaarskywe, wat hoë vlakke van B. cinerea op onbespuite steggies onder die twee steriliteitskondisies getoon het, is verrotting op beide kultivars betekenisvol deur die fungisiedes verlaag. Dit het egter nie vir die ander dele, waarop daar 'n lae voorkoms van B. cinerea onder die twee steriliteitskondisies was, gegeld me. Die studie met trosse het getoon dat droë, luggedraagde konidia en fungisiednewels beide oop en kompakte trosse vanaf blomstadium tot oes penetreer en eweredig op die verskillende dele land. Met blomstadium was die hoeveelheid B. cinerea in onbespuite trosse hoog op laterale en korrelstele, maar laag op die embrios. Onbespuite, intakte trosse was hoogs vatbaar vir B. cinerea by blomstadium en het simptome van vaalvrot ontwikkel. Die fungisiede het siekte-uitdrukking by blomstadium voorkom, maar kon nie infeksie voorkom me. Onbespuite trosse wat op ander stadia geïnokuleer is, het geen siekte-uitdrukking getoon me. Die hoeveelheid B. cinerea was hoër in die ragi, asook in laterale by ertjiekorrel- en trostoemaak stadium, en hoër in korreisteie by oesstadium. Infeksie was konstant laag in die korrelskil. Die fungisiede het 'n differensiële effek op infeksie by die verskillende posisies gehad. In die geval van ragi was die hoeveelheid B. cinerea drasties deur elke fungisied by alle groeistadia verlaag. In laterale was dit effektief by ertjiekorrel- en trostoemaakstadium verminder. By hierdie twee posisies waar die hoeveelheid B. cinerea hoog was, is daar egter betekenisvolle verskille in die doeltreffendheid van fungisiedes gevind. Hierdie studie toon dat as fungisiede behoorlik in kommersiële wingerde tussen botvorming en blomstadium, en tydens blom- en trostoemaakstadium toegedien word, infeksie en siekte-uitdrukking, en dus ook die epifitotiese ontwikkeling van B. cinerea, voorkom behoort te word.

Thesis (MSc (Genetics))--Stellenbosch University, 2008.
The vine mealybug, Planococcus ficus (Signoret), is a severe pest of grapevine in many grape and wine producing countries around the world. It is renowned not only for the considerable damage it infers to grapevine of its own accord, but in particular for its role in transmitting deleterious viral diseases such as grapevine leafroll disease, Kober stem grooving, Shiraz disease and corky bark. Incidentally, it is an exceptionally tenacious antagonist of grapevine, being resistant to both chemical and biological control mechanisms. As a result, finding an effective strategy for P. ficus control has become a main priority of viticultural industries worldwide. Possible implementation of biotechnological approaches to pest management has resulted in a need for P. ficus genetic data - of which there are currently very little available. The transcribed genes of an organism can be captured in a cDNA library, and the sequences of the various transcripts can then be characterized. In this study altogether five cDNA libraries were constructed from the transcribed sequences of Planococcus ficus (Signoret). Instrumental to their construction was the identification of an RNA extraction protocol that provided large quantities of high quality RNA from mealybugs. The five cDNA libraries were the result of a set of modifications to the Creator™ SMART™ cDNA Library Construction Kit (used for Primary Library construction), and differed mainly with regards to range of insert sizes they contain. Whereas an abundance of short fragments were found in the Primary Library (42% of screened inserts 60.5 kb, and 20% >1 kb), the Fractionated Libraries contained inserts of specific size ranges that were more-or-less equally represented. The broadest size range was found in Fractionated Library 4, for which a uniform distribution over the range 0.25 kb - 4 kb was observed. Average insert sizes of Fractionated Libraries 1 to 4 were estimated at 0.25 kb, 0.5 kb, 1 kb and 2 kb respectively. These results demonstrated the importance of using a protocol designed to circumvent the bias towards incorporation of shorter transcripts in cDNA libraries. Although the libraries were not exhaustively analyzed, the outcome of a pilot investigation indicated that 41% of the submitted sequences had matches in the non-redundant database of the National Center for Biotechnology Information (NCBI, E-value 6 10-5), and that approximately 82% of these were of insect origin. Moreover, two potential targets for an RNAi-mediated approach to P. ficus pest control were identified. With one exception, these sequences seemed to be unique to arthropods. Future research needs to investigate the efficiency by which these sequences are able to constrain P. ficus proliferation, and their suitability for grapevine transformation.

Septoria ampelina causes a disease of grapes known as septoria leaf spot. This study was done to determined which of the fungicides currently used to control the various diseases of grapes, plus one experimental fungicide, is the most effective in controlling septoria leaf spot. Both in vitro and in vivo methods were used. In vivo studies examined the systemic and/or protectant activities of the fungicides. The systemic and protectant fungicides included Bayleton, Benlate, Elite (an experimental fungicide), Nova, Rovral and Rubigan. The protectant only fungicides included Captan, Dithane and Kocide. In vitro tests to determine the minimum inhibitory concentration (MIC) for each fungicide (e.g., the concentration of the fungicide that prevents the fungus from forming colonies on the PEA-fungicide medium), indicate that Benlate (MIC = 0.1 ppm) and Elite (MIC = 1.0 ppm) have the greatest potential'to control septoria leaf spot of grape. These are followed by Dithane, Nova and Rubigan (MIC = 2.0), which in turn are followed by Bayleton and Captan (MIC = 50.0 ppm). Kocide and Rovral did not inhibit fungal growth at concentrations up through 100 ppm. Although all the fungicides tested significantly reduced the incidence of septoria leaf spot in vivo, Benlate and Elite were the most effective fungicides (both in systemic and protectant application).
Department of Biology

Thesis (MSc (Plant Pathology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: Esca is a disease affecting grapevines and is potentially devastating as there are economic losses due to a decrease in yield, wine quality and berry quality. Vineyards also need to be replaced earlier and therefore esca has a great impact on the wine, table grape and raisin industries. The disease is known to affect vineyards worldwide and has been studied extensively in Europe, but not in South Africa. Esca diseased grapevines were observed for the first time prior to 1981 in South African vineyards. The disease is primarily caused by Phaeoacremonium aleophilum, Phaeomoniella chlamydospora (both causing brown and black wood streaking) and white rot basidiomycete species such as Fomitiporia mediterranea which cause wood rot in the trunks and arms of generally older grapevines. Species of the Botryosphaeriaceae and Phomopsis (mainly Phomopsis viticola) and Eutypa lata have also been isolated from esca diseased vines, but their association with esca is unclear. Some of the symptoms associated with the disease on most grapevine cultivars include ‘tiger-stripe’ foliar symptoms, apoplexy and berry symptoms such as shriveling, discoloration and ‘black measles’. These external symptoms as well as internal symptoms are thought to be a result of toxin and enzyme production by the fungi involved. Symptom expression is erratic and varies from year to year making investigations into the causal fungi and the toxins and enzymes secreted in planta difficult. Vines with internal or external symptoms of esca were sampled in this study from table and wine grape cultivars in 37 towns in the Western Cape, Northern Cape and Limpopo provinces. The majority of sampled vines were over ten years of age, but vines as young as two to three years were also found to be infected. The external symptoms included dieback, tiger striped leaves, berry symptoms (shriveling, insufficient colouring and black spots) and apoplexy. These symptoms resembled those found on grapevines in Europe, Australia and the USA. The internal symptoms found were also similar to European symptoms and included white rot, black and brown wood streaking, brown necrosis within white rot, sectorial brown necrosis and central brown/ red/ black margin. The fungi mostly isolated from the white rot were the basidiomycetes. Black and brown wood streaking was primarily caused by Phaeomoniella chlamydospora. Brown necrosis within the white rot was caused by Phaeomoniella chlamydospora and less frequently by Phaeoacremonium spp., Eutypa lata, Botryosphaeriaceae and Pleurostomophora richardsiae. The sectorial brown necrosis and the central/ brown/ red/ black margin were dominated by Phaeomoniella chlamydospora. The fruiting bodies of the basidiomycetes were found on only a few grapevines. The fungal species associated with the internal wood symptoms were characterized on cultural growth patterns, morphology as well as phylogenetic inference. The gene areas sequenced included the internal transcribed spacers and the 5.8S rRNA gene for the basidiomycetes and Phomopsis isolates, the partial b-tubulin gene for Phaeoacremonium isolates and the partial translation elongation-1a gene for the Botryosphaeriaceae isolates. The basidiomycete isolates fell into ten taxa within the Hymenochaetales of which two could be linked to known genera, namely Fomitiporia and Phellinus. The ten basidiomycete taxa do not correspond to any published sequences. Eutypa lata, Diaporthe ambigua, Diplodia seriata, Neofusicoccum australe, Neofusicoccum parvum, Phomopsis viticola, Phomopsis sp. 1, Phaeomoniella chlamydospora and six species of Phaeoacremonium including P. aleophilum, P. alvesii, P. parasiticum, P. iranianum, P. mortoniae and P. sicilianum were also isolated of which the latter three are reported for the first time in South Africa. To understand the role of the basidiomycetes in the complex, toxin and enzyme analyses was determined for these fungi. Selected basidiomycete isolates were grown up in liquid broth and extractions performed to test for the presence of 4-hydroxy-benzaldehyde. All of the basidiomycete isolates were able to produce this toxin which is known to be phytotoxic. The basidiomycetes were then tested for the presence of certain wood degrading enzymes. All of the taxa were able to produce manganese peroxidase. Laccase was produced by all taxa, except Taxon 8. Lignin peroxidase was produced by Taxa 1, 2, 7, Fomitiporia sp. and the Phellinus sp. All the basidiomycete isolates were able to produce cellulose and none were able to produce xylanase. These enzyme tests showed that the basidiomycetes produce a wide variety of enzymes which are able to degrade cellulase and lignin which are both structural components of wood. Given the wide distribution of esca in the grape growing regions investigated in South Africa and the diverse amount of species found, this disease must surely be seen as a limiting factor to the productive lifespan of vineyards and quality of produce. Preventative measures such as sanitation and pruning wound protection contribute to the management of the disease, but many questions still remain about the synergy of the causal fungi, epidemiology and management of esca.
AFRIKAANSE OPSOMMING: Esca is ‘n wingerd siekte wat potensieel skade kan aanrig as gevolg van ekonomiese verliese weens verlaagde opbrengs, wyn kwaliteit en vrug kwaliteit. Wingerde moet ook vroeër vervang word en daarom het esca ’n groot impak op die wyn, tafeldryf en rosyne industrieë. Esca word wêreldwyd gevind op wingerd en is al intensief nagevors in Europa, maar nog nie in Suid-Afrika. Esca is vir die eerste keer in die 1980’s in Suid-Afrikaanse wingerde gerapporteer. Die primêre veroorsaakende organismes van esca is Phaeoacremonium aleophilum, Phaeomoniella chlamydospora wat bruin en swart vaatweefsel verkleuring veroorsaak en basidiomycete spesies soos Fomitiporia mediterranea wat wit verotting veroorsaak in die stam en arms van ouer wingerd. Spesies van die Botryosphaeriaceae en Phomopsis (hoofsaaklik Phomopsis viticola) en Eutypa lata is ook al vanaf esca simptome geïsoleer, maar hul assosiasie met die siekte is nie duidelik nie. Algemene simptome wat voorkom op die meeste wingerd kultivars met esca sluit in ‘tiger-stripe’ blaar simptome, apopleksie en vrug simptome soos verdroging, verkleuring en spikkels (black measles). Interne en eksterne simptome kan wees as gevolg van toksiene en ensiem produksie van die swamme wat betrokke is by esca. Eksterne simptoom uitdrukking is wisselvallig en varieer van jaar tot jaar. Dit bemoelik die bestudering van die swamme en die toksiene en ensieme wat afgeskei word in planta. Wingerd monsters met eksterne en interne simptome is versamel van tafel en wyndruif kultivars in 37 dorpe in die Wes-Kaap, Noord-Kaap en Limpopo provinsies. Die meerderheid monsters was ouer as tien jaar maar wingerde wat twee tot drie jaar oud was, was ook gevind. Die eksterne simptome wat op hierdie kultivars gevind is het terugsterwing, ‘tiger striped’ blare, vrug simptome (verkrimping en onvoldoende verkleuring) en apopleksie ingesluit. Hierdie simptome stem ooreen met soortgelyke simptome gevind op wingerd in Europa, Australië en die VSA. Interne simptome was ooreenstemmend met simptome wat gevind word in Europa. Die interne simptome het wit verotting, bruin en swart streepvorming, bruin nekrose met wit verotting, sektoriale bruin nekrose en sentrale bruin/ rooi/ swart kante ingesluit. Basidiomycete swamme is meestal uit die wit verotting gedeeltes geïsoleer. Swart en bruin hout streepvorming was meestal deur Phaeomoniella chlamydospora veroorsaak. Bruin nekrose binne die wit verotting was meestal deur Phaeomoniella chlamydospora veroorsaak en in ‘n mindere mate deur Phaeoacremonium spp., Eutypa lata, Botryosphaeriaceae en Pleurostomophora richardsiae. Phaeomoniella chlamydospora was die hoof veroorsakende organisme van sektoriale bruin nekrose en die sentrale bruin/ rooi/ swart kante. Vrugliggame van die basiodiomycete is op enkele wingerde gevind. Swam soorte wat geassosieer word met die interne hout simptome was verder gekarakteriseer op kultuur groei, morfologiese eienskappe, en filogenetiese analise. Die geen areas waarvan die basis paar volgorde bepaal was sluit in die interne getranskribeerde spasies en die 5.8S rRNA geen vir die basidiomycete en Phomopsis isolate, die gedeeltelike btubulien geen vir Phaeoacremonium isolate en die gedeeltelike translasie velenging-1a geen vir die Botryosphaericeae isolate. Die basidiomycete isolate was versprei oor tien taksons binne die Hymenochaetales waarvan twee genusse gekoppel kon word aan die genera Fomitiporia en Phellinus. Die tien basidiomycete taksons kom nie ooreen met enige gepubliseerde DNS volgordes. Eutypa lata, Phomopsis viticola, Phomopsis sp. 1, Diaporthe ambigua, Diplodia seriata, Neofusicoccum parvum, Neofusicoccum australe, Phaeomoniella chlamydospora en ses spesies van Phaeoacremonium insluitend P. aleophilum, P. alvesii, P. parasiticum, P. iranianum, P. mortoniae en P. sicilianum is ook geïsoleer. Hierdie is die eerste keer dat P. iranianum, P. mortoniae en P. sicilianum in Suid-Afrika gerapporteer word. Om die rol wat die basidiomycete in die siekte-kompleks speel beter te verstaan is toksien en ensiem analises uitgevoer. Geselekteerde basidiomycete isolate is gekweek in vloeibare groei medium en ekstraksies uitgevoer om te toets vir die teenwoordigheid van 4- hydroxy-benzaldehyde. Al die basidiomycete isolate kon 4-hydroxy-benzaldehyde, wat bekend is om fitotoksies te wees, produseer. Die basidiomycete isolate was verder getoets vir die produksie van spesifieke hout afbrekende ensieme. Al die basidiomycete taksons kon mangaan-peroksidase produseer. Lakkase was geproduseer deur al die taksons, uitsluitend Takson 8. Lignien-peroksidase was geproduseer deur Taksons 1, 2, 7, Fomitiporia sp. en die Phellinus sp. Al die basidiomycete isolate kon sellulose produseer, maar geen kon xilanase produseer. Die ensiem analises het gewys dat die basidiomycete wat moontlik betrokke is by esca ‘n wye reeks van ensieme kan produseer wat sellulose en lignien kan degradeer. Sellulose en lignien is beide strukturele komponente van hout. Weens die wye verspeiding van esca geaffekteerde wingerde in Suid Afrika en die wye reeks van spesies wat betrokke is by die siekte kompleks moet esca sekerlik gesien word as een van die beperkende faktore op die produktiewe leeftyd van wingerde en die kwaliteit van druiwe wat geproduseer word. Sanitasie en snoeiwond beskerming is voorkomende maatreëls wat ingestel kan word om die effek en verspreiding van esca te beperk maar daar is nog baie vrae wat antwoorde benodig oor die sinergie van die veroorsakende swamme, epidemiologie en bestuur van esca.

Dissertation (PhD (Agric))--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: During the past few years a drastic reduction has been noted in the survival rate of grafted grapevines in nurseries, as well as in young vineyards in the Western Cape Province of South Africa. Circumstantial evidence suggested that Cylindrocarpon spp., which cause black foot disease of grapevine, were associated with this decline. Black foot disease of grapevine is a relatively new, and as yet poorly known disease affecting vines in various countries where grapevines are cultivated. Primary aims of this research have been (1) to conduct nursery surveys in order to determine which fungi are involved in the decline phenomenon, with special reference to the involvement of Cylindrocarpon spp., (2) to identify and characterise the organisms believed to be the causal organisms of black foot disease, and (3) the development of control and/or management strategies to prevent or eradicate Cylindrocarpon infections. Nursery grapevines were sampled at different stages from three commercial nurseries in the Wellington area of the Western Cape Province and were investigated during the 19992000 season by means of destructive sampling. The first samples were taken in September from callused cuttings prior to planting in nurseries. After planting, asymptomatic rooted cuttings were selected from nurseries after 3, 6 and 9 months. Isolation studies clearly demonstrated that different “Cylindrocarpon spp.” infected cuttings from nursery soils. These species rarely occurred in rootstock propagation material prior to planting. At the time of planting, the susceptible basal ends (especially the pith area) of most of the nursery cuttings are partly or even fully exposed. Callus roots also break during the planting process, resulting in small wounds susceptible to infection by soilborne pathogens. The isolation studies revealed that the first infections occurred in the roots, followed by infections of the rootstocks. These infections increased progressively during the course of the growing season. Substantial variation in cultural and morphological characters was observed among the Cylindrocarpon isolates obtained from the nursery survey, as well as from isolations that were made from diseased grapevines. Morphological and phylogenetic studies were conducted to identify these “Cylindrocarpon spp.” and to establish their association with black foot disease. Sequences of the partial nuclear large subunit ribosomal DNA (LSU rDNA), internal transcribed spacers 1 and 2 of the rDNA including the 5.8S rDNA gene (ITS), and partial β-tubulin gene introns and exons were used for phylogenetic inference. Phylogenetic analyses confirmed the diversity observed among the isolates and four Cylindrocarpon-like species were identified. One of these species was initially identified as Cylindrocarpon destructans. However, further research revealed C. destructans to represent a species complex. Grapevine isolates of “C. destructans” proved to be identical to the ex-type strain of Cylindrocarpon liriodendri, which also produced a teleomorph, Neonectria liriodendri in culture. A second species was newly described in this study as Cylindrocarpon macrodidymum (Neonectria macrodidyma). The two remaining Cylindrocarpon-like species were placed in a new genus, Campylocarpon. The two species were named Campylocarpon fasciculare and Campylocarpon pseudofasciculare. Pathogenicity studies confirmed that all four species were able to reduce root and shoot mass significantly. Knowledge obtained pertaining to the disease cycle of black foot disease suggest that suitable management strategies should focus on prevention of primary infection in nurseries. However, at present, no fungicides are registered for control of this disease in South African vineyards or nurseries. Thirteen fungicides were screened in vitro for mycelial inhibition of these pathogens. Prochloraz manganese chloride, benomyl, flusilazole and imazalil were the most effective fungicides tested, and were subsequently included in semi-commercial field trials. Basal ends of grafted cuttings were dipped (1 min) in various chemical and biological treatments prior to planting in open-rooted nurseries. Black foot pathogens were not isolated from grafted cuttings prior to planting in nurseries. Additional treatments involved soil amendments with Trichoderma formulations and hot water treatment (50°C for 30 min) of dormant nursery grapevines. Field trials were evaluated after a growing season of eight months. The incidence of black foot pathogens was not significantly and/or consistently reduced by the majority of chemical or biological treatments. However, these pathogens were not isolated from uprooted plants that were subjected to hot water treatment. It is therefore recommended that hot water treatment of dormant nursery plants be included in an integrated strategy for the proactive management of black foot disease in grapevine nurseries.
AFRIKAANSE OPSOMMING: Gedurende die afgelope paar jaar is ‘n drastiese afname waargeneem in die sukses van geënte wingerdplante in kwekerye, sowel as jong wingerde van die Wes-Kaap. Omstandigheidsgetuienis dui daarop dat Cylindrocarpon spp., wat die wingerdsiekte swartvoet veroorsaak, geassosieer word met hierdie agteruitgang. Swartvoet is ‘n relatiewe nuwe siekte waarvan daar baie min inligting bekend is, alhoewel dit voorkom in verskeie lande waar wingerd verbou word. Die primêre doel van navorsing was (1) om opnames in wingerdkwekerye uit voer om te bepaal watter swamme betrokke is by die verskynsel van agteruitgang, met spesiale verwysing na die betrokkenheid van Cylindrocarpon spp., (2) om die organismes te identifiseer en te karakteriseer wat daarvan verdink word dat hulle die siekte swartvoet veroorsaak, en (3) om beheer en/of bestuurspraktyke te ontwikkel om Cylindrocarpon infeksies te voorkom of uit te wis. Kwekeryplantjies in drie kommersiële kwekerye in die Wellington omgewing van die Wes-Kaap is gedurende verskillende tye gedurende die groeiseisoen gemonitor. Die opnames het plaasgevind gedurende die 19992000 seisoen deur middel van destruktiewe monsterneming. Die eerste monsters is geneem in September nadat die stokkies geënt en gekallus is en voordat dit in die kwekery geplant is. Na plant is asimptomatiese, gewortelde plante vanuit die kwekerye na 3, 6 en 9 maande uitgehaal. Isolasiestudies dui duidelik daarop dat verskillende “Cylindrocarpon spp.” plante vanuit die kwekerygrond geïnfekteer het. Hierdie spesies het selde voorgekom in onderstok-voortplantingsmateriaal voor plant. Tydens plant is die vatbare basale gedeelte, veral die pit, van die meeste geënte stokkies gedeeltelik of selfs volledig blootgestel. Kalluswortels breek ook tydens plant wat wonde laat vir infeksie deur grondgedraagde siektes. Die isolasiestudies dui ook daarop dat die eerste infeksies in die wortels plaasgevind het, gevolg deur infeksies van die onderstokke. Hierdie infeksies het toenemend voorgekom gedurende die verloop van die groeiseisoen. Substansiële variasie in kultuur- en morfologiese eienskappe is waargeneem in die Cylindrocarpon isolate wat tydens die kwekeryopnames versamel is, sowel as van isolasies wat gemaak is uit siek plante. Morfologiese en filogenetiese studies is uitgevoer om hierdie “Cylindrocarpon spp.” te identifiseer en hul betrokkenheid by die siekte swartvoet uit te klaar. Gedeeltelike DNS volgordes van die groot ribosomale subeenheid (“LSU rDNA”), interne getranskribeerde spasiëerderarea (“ITS1, “ITS2”), insluitend die 5.8S rRNS geen, en gedeeltelike β-tubilien geen introns and eksons is gebruik vir filogenetiese analise. Filogenetiese analises het die diversiteit wat waargeneem is tussen die verskillende isolate bevestig deurdat vier Cylindrocarpon-agtige spesies geïdentifiseer is. Een van hierdie spesies is aanvanklik geïdentifiseer as Cylindrocarpon destructans. Verdere navorsing het egter daarop gedui dat C. destructans ‘n spesie-kompleks verteenwoordig. “C. destructans” afkomstig van wingerd blyk identies te wees aan die ex-tipe isolaat van Cylindrocarpon liriodendri, wat ook ’n teleomorf, Neonectria liriodendri in kultuur vorm. ’n Tweede spesie is nuut beskryf in hierdie studie as Cylindrocarpon macrodidymum (Neonectria macrodidyma). Die twee oorblywende Cylindrocarpon-agtige spesies is geplaas in ‘n nuwe genus, Campylocarpon. Die twee spesies staan bekend as Campylocarpon fasciculare en Campylocarpon pseudofasciculare. Patogenisiteitstudies het bevestig dat al vier spesies die vermoë het om wortel- en lootmassa van wingerdplant drasties te verlaag. Kennis wat opgedoen is rakende die lewensiklus van swartvoet dui daarop dat bestuurspraktyke daarop moet fokus om primêre infeksies in wingerdkwekerye te voorkom. Op die oomblik is daar egter geen fungisiedes geregistreer vir die beheer van die siekte in Suid- Afrikaanse wingerde of kwekerye nie. Dertien fungisiedes is in vitro geëvalueer om te bepaal of dit miseliumgroei van hierdie swamme kan inhibeer. Prochloraz mangaan chloried, benomyl, flusilasool en imazalil was die effektiefste fungisiedes wat ondersoek is, en is gevolglik ingesluit in semi-kommersiële veldproewe. Die basale gedeelte van geënte stokkies is gedoop (1 min) in verskeie chemies en biologiese behandelings voordat dit geplant is in die kwekerye. Patogene wat geassosieer word met swartvoet is nie vanuit geënte stokkies geïsoleer voordat dit in die kwekerye geplant is nie. Addisionele behandelings het bestaan uit grondtoevoegings met Trichoderma formulasies, sowel as warmwaterbehandeling (50°C vir 30 min) van dormante kwekeryplante. Die veldproewe is geëvalueer na ‘n groeiseisoen van 8 maande. Die voorkoms van swartvoet patogene is nie betekenisvol/konstant verlaag deur die meeste chemies en biologiese behandelings nie. Hierdie patogene is egter nie vanuit plante geïsoleer wat na uithaal aan warmwaterbehandeling blootgestel is nie. Dit word dus aanbeveel dat warmwaterbehandeling van dormante kwekeryplante deel word van ‘n geïntegreerde strategie vir die pro-aktiewe beheer van swartvoet in wingerdkwekerye.

Thesis (MSc (Genetics))--University of Stellenbosch, 2009.
Grapevine Vitivirus A (GVA), genus Vitivirus, family Flexiviridae is a well characterised single-stranded RNA virus that has been implicated in the grapevine diseases, Kober stem grooving and Shiraz disease. The virus infects both its host, Vitis vinifera and the experimental model plant, Nicotiana spp.. Biological studies performed on the virus in its herbaceous host, Nicotiana benthami- ana, revealed that many divergent variants of the virus exists in South Africa and can induce di erent symptoms in the model plant. Further molecular analysis divided the variants into three molecular groups based on molecular heterogeneity and nucleotide identity. The establishment of an infectious full-length cDNA clone of GVA contributed towards the elucidation of gene functions for 4 of the 5 open reading frames (ORF's), and indicated ORF5 as the pathogenicity determinant within the genome. Further studies also showed that ORF5 encodes for a nucleic acid binding protein that exhibits suppression activity of a plants' natural virus silencing mechanism. Many proteins that have previously been identi ed as the pathogenicity determinant within a viral genome have been found to encode for suppression activity. Although suppression activity has been elucidated within the ORF5 of the Italian cDNA clone of GVA, IS 151, no such study has yet been performed on the divergent South African variants of GVA. Three variants, GTR1-1, GTR1- 2 and GTG11-1, which represent each of the molecular groups (Group III, II and I), were selected for this study. The aim of this study was to visually elucidate suppression activity of RNA transgene silencing by the ORF5's of GTR1-1, GTR1-2 and GTG11-1 in a transient expression assays in transgenic N. benthamiana (line 16c). Pathogenicity studies for these variants were also performed. The ORF5 of the infectious full-length clone, GVA118, which can also serve as an expression vector, was deleted and provided with restriction enzyme sites into which the respective ORF5s and the marker genes, GFP and GUS could be cloned directionally. Infectivity, symptom development and systemic movement were compared between the di erent full length clones after co-in ltration in N. benthamiana. Preliminary results obtained in this study failed to visually indicate any suppression activity encoded by the ORF5 of GTR1-1, GTR1-2 and GTG11-1. The deletion of ORF5 within GVA118 was successful and rendered the infectious full length clone asymptomatic. Directional cloning of the ORF5 of GTR1-1 into the unique restriction enzymes provided previously, resulted in much milder symptoms than those observe for GTR1-2 and GTG11-1. No GFP and GUS accumulation could be detected. This study has established an infectious full-length cDNA clone, pBINSN-e35SGVA118 ORF5-1-1-pA, that can possibly induce much milder symptoms in the herbaceous host, N. benthamiana. This construct can be further characterised as a possible expression vector of foreign proteins in herbaceous hosts and grapevine.

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: Several attempts have been made to reduce Botrytis cinerea grey mould in vineyards and in storage by means of biological control. However, the so called "silver bullet" approach in utilising a single antagonist, has its limitations when compared with synthetic fungicides. Often the antagonist has a limited spectrum of activity and the duration of its effectiveness is less than that provided by synthetic fungicides. Furthermore, antagonists are more likely to be effective in preventing initial infection rather than resumption of latent infection. Therefore, due to the various infection sites in grape bunches utilised by B. cinerea and the fact that the pathogen can remain latent in the grapevine tissue, it may be possible to obtain effective control of the pathogen by integrating fungicides and different biological control agents each aimed at a different site in grape bunches, protecting the bunch at the various phenological stages of growth and under different micro climatic conditions. In this study the potential of three fungal antagonists (Glioc/adium roseum, Uloc/adium atrum and Trichoderma harzianum) and one yeast (Trichosporon pullulans) to colonise different sites in grape bunches, and to reduce B. cinerea infection, was investigated in commercial vineyards. As the biological control agents were used in an integrated system, the effect of various fungicides frequently applied to local vineyards on the organisms was also investigated. Fungicide trials were conducted taking into account two possible scenarios. Firstly, the possible effect of fungicides applied to the vineyard after an application of the biological control agent or shortly before the application of the biocontrol agent. This entailed exposing the biocontrol agents to relatively low concentrations of the active ingredient of the fungicides, similar to the residue levels to which these organisms would be exposed under field conditions. Secondly, the possibility of applying the organisms and the fungicides at the same time by making use of spray tank mixtures. This meant exposing the biocontrol agents to relatively high doses of the active ingredient of the various fungicides. Mycelial growth and germination tests were performed on agar in Petri dishes to determine the effect of fungicides. It was assumed that if the fungicide effectively inhibits the antagonist at 2.5 !-lg a.Uml, the fungicide and antagonist can not be used in an integrated programme. Based on this criterium, T harzianum can not be applied to vineyards with penconazole, mancozeb/metalaxyl, pyrifenox or mancozeb. In addition T harzianum can not be applied as tank mixtures with iprodione. However, T harzianum can be used in conjunction with pyrimethanil, folpan, iprodione, fosetyl-Al and copperhydroxide, provided the chemicals and the antagonist are applied alternately. Gliocladium roseum can not be applied in a tank mixture with pyrimethanil and penconazole, but can be used on grapevine in conjunction with penconazole, pyrifenox, pyrimethanil, iprodione and fosetyl-Al. Ulocladium atrum can not be applied with pyrimethanil and iprodione. Ulocladium atrum can be applied in conjunction with penconazole, pyrifenox, pyrimethanil, iprodione, fosetyl-Al and mancozeb. The fungus can be applied in a tank mixture with penconazole and pyrifenox. The antagonists were applied as conidial suspensions to bunches at various phenological stages in commercial vineyards planted with the wine grape cultivar Chardonnay in the Stellenbosch region, or the table grape cultivar Dauphine planted in Paarl region. Bunches were collected 2 wk after application, surface-sterilised and used for determining antagonist colonisation and B. cinerea infection at specific sites in the bunches. In Chardonnay, the antagonists colonised the different sites, but colonisation during the three seasons was inconsistent and sporadic. Ulocladium atrum and G. roseum colonised floral debris to a degree in the 1996 season. However, in the 1997 season these two antagonists did not develop from floral debris. Trichoderma harzianum colonised floral debris extensively in the 1996 season. In the 1997 season colonisation by T harzianum dropped, but unlike G. roseum and U atrum, T harzianum occurred at a low level in flowers. Ulocladium atrum only colonised bunches during bloom, and was not found in bunches monitored from pea-size stage to véraison. This finding suggests that the saprophyte colonised moribund and dead flower parts occurring in bunches during full bloom to the pre-pea size stage, and is not likely to be found in living tissue. Gliocladium roseum colonised grape berries and pedicels to some degree and T harzianum colonised these grape parts extensively. Botrytis cinerea occurred inconsistently and at low frequencies in the different sites in bunches. It was therefore not possible to comment on the effectivity of the various antagonists in the three seasons during which the trials were performed. However, it was noted that, during the peasize stage in 1996, when high levels of B. cinerea were recorded, T harzianum controlled these infections in the pedicels more effectively than any other treatment.
AFRIKAANSE OPSOMMING: ONDERDRUKKING VAN BOTRYTIS CINEREA DEUR ANTAGONISTE IN LEWENDE, AFSTERWENDE EN DOOIE WINGERDWEEFSEL Die benadering om Botrytis cinerea verrotting van wingerd met behulp van 'n enkele biologiese beheeragent in plaas van met sintetiese fungisiede te beheer, het sekere beperkinge. Antagoniste het dikwels 'n beperkte spektrum van aktiwiteit, en die duur van hul effektiwiteit is minder as dié van fungisiede. Antagoniste is gewoonlik ook minder effektief in die beheer van latente infeksie. Die patogeen het verder die opsie om druiwetrosse deur verskillende infeksieweë te koloniseer. Fungisiede kan druiwetrosse beter teen infeksie deur veelvuldige infeksieweë beskerm as 'n enkele antagonis. In die lig hiervan is die beheer van die patogeen deur 'n kombinasie van fungisiede en verskillende biologiese beheeragente, wat elk gemik is om 'n ander infeksiepunt in die druiwe te beskerm, ondersoek. Drie swamagtige antagoniste (Glioc/adium roseum, Uloc/adium atrum en Trichoderma harzianum) en een gis (Trichosporon pullulans) is in die ondersoek gebruik. Voorloper ondersoeke, waar twee moontlike scenarios in ag geneem is, is met fungisiede uitgevoer. In die eerste scenario is die effek van fungisiede, aangewend op wingerd kort vóór aanwending van die biologiese beheeragent, of kort ná aanwending, ondersoek. Hierdie proef het die blootstelling van die biologiese beheeragent aan relatief lae konsentrasies van die aktiewe bestanddeel van die fungisied, vergelykbaar met residuvlakke waaraan die organismes onder veldtoestande blootgestel sou word, behels. Tweedens is die moontlikheid om antagoniste en fungisiede gelyktydig as spuitpompmengsels toe te dien, ondersoek. In hierdie proef is die biologiese beheeragente aan relatief hoë dosisse van die aktiewe bestanddeel van verskillende fungisiede blootgestel. Miseliumgroei en ontkiemingstoetse is op agar in Petribakkies uitgevoer om die effek van die fungisiede te bepaal. As kriterium is aanvaar dat indien 'n fungisied die antagonis effektief by 2.5J..lglml aktiewe bestanddeel inhibeer, die fungisied en antagonis nie in 'n geïntegreerde program gebruik kan word nie. Gebaseer op hierdie kriterium kan T harnzianum nie aangewend word in 'n wingerd wat met penconazole, mancozeb/metalaxyl, pyrifenox of mancozeb behandel is nie. Ook kan T harzianum nie in 'n spuitpompmengsel met iprodione aangewend word nie. Trichoderma harzianum kan egter saam met pyrimethanil, folpan, iprodione en fosetyl-Al gebruik word, mits dié chemikalieë en die antagonis afwisselend aangewend word. Glioc/adium roseum kan nie in 'n spuitpompmengsel met pyrimethanil en penconazole aangewend word nie, maar kan saam met penconazole, pyrifenox, pyrimethanil, iprodione en fosetyl-Al gebruik word. Uloc/adium atrum kan nie saam met pyrimethanil, iprodione en fosetyl-Al gebruik word nie. Die swam kan wel in 'n spuitpompmengselmet penconazole en pyrifenox aangewend word. In verdere proewe is die antagoniste as spoorsuspensies op trosse op verskillende groeistadia in kommersiële wingerde, wat met die wyndruitkultivar Chardonnay of die tafeldruifkultivar Dauphine aangeplant is, ondersoek. Trossies is twee weke na toediening versamel, oppervlakkig gesteriliseer en gebruik om vlakke van antagoniskolonisasie en B. cinerea infeksie op spesifieke nisse in die trosse te bepaal. In die geval van Chardonnay het die antagoniste die verskillende nisse gekoloniseer, maar die kolonisasie was sporadies en nie konstant gedurende die drie seisoene van ondersoek nie. Uloc/adium atrum en G. roseum het blomdeeltjies tot 'n beperkte mate in die 1996 seisoen gekoloniseer, maar nie in die daaropvolgende seisoen nie. Daarteenoor het T. harzianum blomdeeltjies ekstensief in die 1996 seisoen gekoloniseer, en in 'n beperkte mate in die daaropvolgende seisoen. Uloc/adium atrum kon nie trosse van ertjiekorrelgrootte tot deurslaan vestig nie. Hierdie bevinding dui daarop dat die saprofiet afsterwende en dooie blomdeeltjies, wat van volblom tot ertjiekorrelstadium in die trosse voorkom, koloniseer, maar dat dit nie in lewende weefsel voorkom nie. Daarteenoor het T. harzianum die verskillende trosdele ekstensief gekoloniseer. Botrytis cinerea het gedurende die drie seisoene wisselvallig en teen lae frekwensies in die verskillende nisse in die trosse voorgekom. Dit was gevolglik nie moontlik om 'n konkrete afleiding oor die effektiwiteit van die verskillende antagoniste as biobeheeragente van B. cinerea te maak nie. In die geval van Dauphine was die onderskeie organismes swak koloniseerders van blomdeeltjies. Trichoderma harizanum kon egter die lewende trosdele koloniseer. Kolonisasievlakke was laag en was nooit meer as 50% nie. In beide seisoene het die kolonisasievermoë van T. harzianum drasties ná trostoemaak gedaal. Daarteenoor het beide G. roseum en U atrum tydens al die ontwikkelingstadia die lewende trosdele swak gekoloniseer. Botrytis cinerea het ook uiters sporadies en teen baie lae vlakke voorgekom. Die bevindinge het getoon dat klimaatsomstandighede wat in tafeldruifwingerde in die Wes-Kaap heers, nie geskik is vir die vestiging van die biologiese beheeragente wat in die studie ondersoek is nie.

Bibliography: leaves 182-217. This study was conducted to determine the etiology of a blight disease of chickpea in south-eastern Australia and the factors affecting disease development. The disease had previously been identified as phoma blight. Pathogenicity testing revealed two isolates subsequently identified as Asochyta rabiei, the first conclusive identification in the southern hemisphere. Greenhouse screening of chickpea varieties identified types resistant to ascochyta blight. The effects of plant age and environmental conditions on disease development were investigated under controlled conditions in growth rooms. Seedlings were more susceptible than older plants. The optimum conditions for ascochyta blight were 20° C and a 48-96 h period of leaf wetness. Through field trials it was found that disease intensity increased over time, especially in cv. Desavic. The means of penetration of the chickpea host was established in histological studies. This study provided advance warning of this disease for the expanding chickpea industry, and has allowed the implementation of appropriate disease management strategies. It is recommended that cv. Desavic should not be grown where ascochyta blight is likely to be a problem.

Bibliography: leaves 224-236. The study aimed to determine the distribution of both P. thornei and P. neglectus in South Australia. Also to study the field and laboratory population dynamics of P. thornei in relation to wheat yields, to determine its host range on a variety of cereal and non-leguminous hosts and to identify possible sources of nematode resistant wheat cultivars/varieties. Preliminary experiments studied the involvement of root rotting fungi with the nematode in wheat disease.

Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Grapevine virus E (GVE) is a newly identified virus that has been detected in an established vineyard in South Africa. This virus is a member of the genus Vitivirus, family Flexiviridae. Members of this genus are known to infecte grapevine and are associated with various disease complexes, such as the Rugose wood complex (RWC) and Shiraz disease (SD). However, the role and impact of GVE in South African vineyards are still unknown. It is important to study these viruses to determine how they infect and the possible impact they may have on vine health. The accurate and early detection of grapevine viruses is the first important step in disease management. In this study, reverse transcription-polymerase chain reaction (RT-PCR), double antibody sandwich enzyme linked immunesorbent assay (DAS-ELISA) and quantitative (q)RT-PCR were used for the detection of GVE in the vineyard (Vitis vinifera cv Merlot) where GVE was first identified in South Africa. Reverse transcription-PCR was used for detection and determining the incidence of GVE. The incidence was as low as 3% in the vineyard surveyed. All the GVE positive plants were co-infected with GLRaV-3 and no disease association could therefore be made. Evaluation of the Bioreba Grapevine virus A (GVA) DAS-ELISA kit showed that it did not detect GVE. No cross-reactivity occurred with epitopes of GVE, confirming this kit to be a valid and specific assay for GVA infection. The relative virus titer of GVE was calculated over the growing season of 2010/2011, using qRT-PCR. No fluctuation in virus titer was observed during that growing season. Transmission experiments were performed in an attempt to transfer GVE from grapevine to an alternative host. Three different transmission buffers as well as nine different herbaceous plant species, that have shown to be susceptible to several plant viruses in previous studies, were evaluated. In these experiments, GVE could not be transmitted to any of the herbaceous species. To further characterize GVE, chimeric clones were constructed with GVA. The ORF2 and ORF5 of GVE were cloned into previously constructed GVA ORF2 and ORF5 deletion mutants. Construction of the chimeric clones, 35S-GVA-GR5-ΔORF2-GVE-ORF2 and 35S-GVA-118-ΔORF5-GVE-ORF5 were successful and they were evaluated for their infectivity in N. benthamiana. The 35S-GVA-GR5-ΔORF2-GVE-ORF2 chimera was able to infect and replicate in these plants and disease symptoms such as yellowing of veins and leaf curling were observed. Virus, derived from this vector, was detected by TPIA, RT-PCR and DAS-ELISA. The 35S-GVA-118-ΔORF5-GVE-ORF5 chimeric vector was not able to infect N. benthamiana as no disease symptoms were observed in any of the infiltrated plants and virus was not detected with serological analysis and RT-PCR. This study was aimed at further characterizing the recently identified virus GVE. Here, insight is given into the prevalence of this virus in the vineyard where it was first identified and attempts to biologically characterize GVE were made.
AFRIKAANSE OPSOMMING: Grapevine virus E (GVE) is „n nuut geïndetifiseerde virus wat onlangs in „n gevestigde wingerd in Suid Afrika opgespoor is. Hierdie virus vorm deel van die genus Vitivirus, familie Betaflexiviridae. Spesies in hierdie genus is bekend vir wingerdinfeksies en word met „n verskeidenheid wingerd siektes geassosieer, soos bv. Rugose wood complex (RWC) en Shiraz siekte (SD). Die rol en impak van GVE is nog onbekend. Dit is dus belangrik om die virus te bestudeer om te bepaal hoe dit infekteer en of dit enige impak het op wingerd gesondheid. Akkurate en vroeë opsporing van virusse is die eerste belangrike stap vir virussiekte beheer. In hierdie studie word tru-transkripsie (TT) – polimerase ketting reaksie (PKR), dubbel teenliggaam (DAS) -ensiem gekoppelde immuno-absorberende analise (ELISA) en qTT-PKR gebruik vir die opsporing van GVE in die wingerd (Vitis vinifera cv Merlot) waar dit vroeër in Suid Afrika geïdentifiseer was. Vir opsporing en bepaling van verspreiding is TT-PKR gebruik. Daar is bepaal dat 3% van die wingerd met GVE geïnfekteer is. Al die GVE-positiewe stokke het ook positief getoets vir GLRaV-3 en geen assosiasie met siekte simptome kon gemaak word nie. Evaluering van die Bioreba GVA DAS-ELISA met GVE positiewe stokke het nie GVE opgespoor nie. Geen kruisreaktiwiteit het plaasgevind met epitope van GVE nie en dus is die DAS-ELISA ʼn betroubare toets vir GVA infeksie. Die relatiewe virus titer van GVE was ook bepaal oor die groeiseisoen van 2010/2011 deur qTT-PKR te gebruik. Geen fluktuasie in virus titer gedurende die groeiseisoen is waargeneem nie. Transmissie eksperimente is gedoen om GVE vanaf wingerd na ʼn alternatiewe gasheer oor te dra. Drie verskillende transmissie buffers en tien verskillende sagteplant spesies, wat voorheen vatbaarheid vir plantvirusse getoon het, is gebruik. In die transmissie eksperimente kon GVE nie na enige van die sagteplante oorgedra word nie. Om GVE verder te karakteriseer is hibried-virusse met GVA gemaak. Die leesraam (ORF) 2 en ORF5 van GVE gekloneer in GVA ORF2 en -ORF5 delesie konstrukte, 35S-GVA-GR5-ΔORF2 en 35S-GVA-118-ΔORF5, onderskeidelik (Blignaut, 2009; Du Preez, 2010). Klonering van die hibried konstrukte, 35S-GVA-GR5-ΔORF2-GVE-ORF2 en 35S-GVA-118-ΔORF5-GVE-ORF5, was suksesvol en is in N. benthamiana geëvalueer. Virus afkomstig van die 35S-GVA-GR5-ΔORF2-GVE-ORF2 hibried konstruk, kon plante suksesvol infekteer en kon repliseer binne hierdie plante. Siektesimptome soos vergeling van die are en rolblaar is ook waargeneem in plante geïnfekteer met hierdie hibried konstruk. Plante is getoets met weefsel afdruk immuno analise (TPIA), TT-PKR en DAS-ELISA en is positief gevind vir virus afkomstig van hierdie konstruk. Die 35S-GVA-118-ΔORF5-GVE-ORF5 hibried kon nie N. benthamiana infekteer nie en geen siektesimptome is waargeneem in enige van die plante geïnfiltreer met hierdie konstruk. Serologiese analise en TT-PKR het ook nie virus in die N. benthamiana plante opgespoor nie. Die doel van hierdie studie was om GVE te karakteriseer. In hierdie studie word insig gegee oor die verspreiding van hierdie virus in Suid Afrika en pogings is gemaak om GVE biologies te karakteriseer.

Papaya (Carica papaya), originating in South America, is widely-grown throughout the tropical and sub-tropical regions of the world. The popularity and versatility of the fruit and commercial uses of papain obtained from papaya latex have made the crop an important component of cropping systems in many developing countries where 98% of production is centred. Papaya ringspot virus (PRSV) is the major limiting factor to papaya production in many countries, particularly those in South­East Asia and South America. Papaya ringspot disease was first detected in Queensland in 1991, with several commercial plantations being severely affected. Effective control of a disease requires an efficient detection system, a knowledge of disease epidemiology under local conditions and an assessment of potential control strategies. These objectives were addressed in this thesis. A Queensland isolate of PRSV-P (338 Wamuran) was purified and polyclonal antiserum produced. The antiserum was used in double-antibody sandwich and plated trapped antigen ELISA formats to detect PRSV in papaya and cucurbit samples. Although papaya sap was shown to inhibit ELISA reactions, antisera to PRSV-338 or PRSV-HA (Hawaii) provided a satisfactory screening assay for all samples tested from papaya and cucurbits. Isolates of PRSV-P and -W from the Philippines, Thailand, Hawaii and Vietnam were serologically indistinguishable in PTA-ELISA using PRSV-338 and PRSV-HA antiserum. The ability of PRSV to spread rapidly within a plantation in the absence of roguing was demonstrated at Bridgeman Downs where virus incidence increased from zero to 95% in six months in plants established adjacent to infected papayas. Despite the capacity of PRSV-P to rapidly spread within a plantation, the distribution of PRSV-P in Queensland has not substantially altered since its detection in papaya in February 1991 in south-east Queensland. Three significant outbreaks have occurred in commercial plantations since 1991 but were contained by roguing infected plants. The slow spread of PRSV-P in Queensland, in contrast to most other countries where the virus occurs, may be due to the physical separation of many plantations and the natural barriers of forest, grassland and non-susceptible crops which have restricted virus spread. Roguing has proved effective in containing local outbreaks of PRSV. The experimental host range of PRSV in Queensland was confined to Cucurbitaceae and Caricaceae. Commercially available cultivars of Citrullus lanatus, Cucumis melo, C. sativus, Cucurbita pepo, C. maxima and C. moschata were all highly susceptible to both PRSV-P and -W following manual inoculation. An isolate of each PRSV-W (DBI) and PRSV-P (338) also infected a proportion of inoculated plants of Benincasa hispida, Citrullus colcynthis, Lagenaria siceraria, Luffa cylindrica and Momordica charantia. When species and accessions of Cucumis and Cucurbita were screened by manual inoculation, Cucumis africanus, C. callosus C. ficifolius, C. leptodermis, C, membranifolius and C. zeyheri were determined as new experimental hosts of PRSV-P and -W. Citrullus colocynthis, Cucumis dipsaceus, C. meeusei and Cucurbita pepo var. fraterna are previously unreported hosts of Australian PRSV-P and -W. Several accessions of Cucumis metuliferus and Cucurbita foetidisima were resistant to PRSV-P (338) and -W (DBI). Isolates of PRSV-P, but not PRSV-W, infected Carica papaya, C. parviflora, C. pentagonia, (babaco) and C. goudotiana but not Carica cauliflora, C. pubescens, C. stipulata, C. quercifolia or Jacaratia spinosa. When 114 plants of the interspecific hybrid Carica papaya x C. cauliflora were inoculated with PRSV-P, 92 of the hybrid plants died, presumably due to genetic incompatibility, before virus assays could be completed. The remaining 22 plants did not develop symptoms and virus was not detected by ELISA or back- inoculation to Cucurbita pepo test plants. The natural host range of PRSV-P in Queensland was confined to Carica species and, importantly, several cucurbit species. Mosaic and mottle symptoms developed in commercial cultivars of pumpkin (Cucurbita maxima), squash (Cucurbita pepo) and zucchini (Cucurbita pepp var melopepo) in two field experiments planted adjacent to infected papaya plants. PRSV-P was confirmed in symptomatic cucurbits by ELISA and inoculation to young plants of Carica papaya. This appears to be the first experimental demonstration that cucurbits are natural hosts of PRSV-P and is discussed in relation to the possible origin of PRSV-P in Queensland. In a separate trial at a location where PRSV did not naturally occur, it was shown that PRSV-P could be transmitted by aphids from PRSV-P inoculated zucchini to papaya plants. In this trial, 21 of 26 papaya plants had developed typical PRSV symptoms nine weeks after transplanting. PRSV-P was not found in samples obtained from 12 common weed species growing in a plantation where PRSV-P - infected papaya plants had been present for several years. Seed transmission of PRSV-P was not detected in plants grown from seed collected from infected plants at Dayboro, Qld, the Philippines and Malaysia. Four cultivars (Red Luck, Known You No. 1, Tainung 5, Cariflora) with reputed tolerance to PRSV-P were compared with the commercial cultivar Richter Gold in a field trial where they were exposed to natural infection by PRSV-P. The period from planting to 50% of plants with symptoms was eight weeks for Richter Gold and from 15 to 22 weeks for the four tolerant cultivars. Cariflora developed the mildest leaf symptoms but had very poor fruit set. Plants of Red Luck, Known You No. I and Tainung 5 developed severe leaf symptoms. Fruit set was greatest in Red Luck and Known You No. 1 after one year's growth. Although none of the cultivars had outstanding tolerance to PRSV-P in Queensland, it was concluded that further selection could be undertaken in Red Luck and Known You No. 1 to increase tolerance levels and adaptability. Despite the very limited molecular variation detected between PRSV isolates from Queensland, considerable biological variation was detected between some PRSV-P isolates. This was particularly marked when the tolerant cultivars and Richter Gold were inoculated with either one of two isolates of PRSV-P (338 or 445) in a glasshouse. Leaf symptoms and the degree of stunting were very severe on plants inoculated with isolate 445. Comparative virus concentrations were inversely correlated with symptom severity. Absorbance values (A41onm) were significantlyhigher (P < 0.01) for both isolates in all four tolerant cultivars compared with Richter Gold and significantly less (P < 0.01) for isolate 445 in Know You No. 1, Tainung 5 and Richter Gold, all of which developed severe leaf symptoms and stunting with this isolate. The possible origins of this variation and the implications to control programs are discussed.

Three pages of addenda pasted inside back cover. Bibliography: leaves 166-189. Rhizoctonia solani is a complex species comprising morphologically basidiomycetous imperfect fungi. This study aimed to determine genetic diversity within R. solani AG-3 causing rhizoctonia disease of potato in South Australia. For this purpose, pectic zymogram, PCR, DNA fingerprinting and RFLP techniques were used in conjunction with traditional plant pathology procedures.

Thesis (MScAgric)--University of Stellenbosch, 2004.
ENGLISH ABSTRACT: Soilborne diseases of grapevines represent a complex problem with limited information available, both locally and internationally. Previous research in South Africa indicated that Phytophthora and Pythium spp. were the most widespread and devastating pathogens in grapevine nurseries and vineyards in the Western Cape province. The local grapevine industry is currently expanding; new cultivars, methods and agricultural chemicals are being used which can affect soilborne pathogens. It has therefore become necessary to reassess the status of soilborne pathogens in nurseries, since information in this regard is crucial for the development of disease management practices for the expanding local grapevine industry. Soilborne fungal genera associated with roots and crowns of declining nursery grapevines were assessed in surveys conducted at three different grapevine nurseries in the Western Cape province. Cylindrocarpon, Fusarium, Pythium, and Rhizoctonia spp. were consistently isolated from roots and crowns of declining nursery grapevines. Cylindrocladiella spp. and Phytophthora cinnamomi were infrequently isolated from diseased roots, crowns and soil whereas Pythium spp. were abundant in most of the soils. Results suggest that the status of soilborne fungal pathogens in grapevine nurseries in the Western Cape province has changed over the last 30 years. The DNA phylogeny and pathogenicity of the isolates of Cylindrocladiella were determined. Four species of Cylindrocladiella occur on grapevines in South Africa, namely C. lageniformis, C. parva, C. peruviana, as well as a new species, described in this study as C. viticola, which forms part of the C. infestans species complex. Pathogenicity trials were inconclusive. Ten Fusarium spp. were isolated from roots and crowns of declining nursery grapevines, namely F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum and F. solani. The dominant species was F. oxysporum, followed by F. proliferatum and F. solani. In pathogenicity trials F. oxysporum and F. solani significantly reduced root volume, root dry mass, length of new shoots, stem diameter and number of leaves, but increased the percentage of chlorotic leaves and root rot severity. Fusarium proliferatum also caused a significant reduction in new shoot growth, number of leaves and increased root rot severity compared to the controls. Fusarium so/ani seems to be more virulent than F. oxysporum, followed by F. pro/iferatum. This is the first report of F. oxysporum, F. pro/iferatum and F. so/ani as pathogens of grapevines in South Africa, and the first report of F. proliferatum as a pathogen of grapevines in the world. Phytophthora cinnamomi was isolated at low frequencies from declined grapevines, although present in the rhizosphere soil. It is possible that the extensive use of downy mildew chemicals in grapevine nurseries may protect grapevines from infection by P. cinnamomi. The effect of chemicals used to combat downy mildew on Phytophthora root rot of nursery grapevines was evaluated in a glasshouse. There was very little discernable effect of the chemicals tested relative to the control plants for the parameters measured and it was concluded that the inoculation technique needed refinement. However, plants treated with phosphorous acid tended to be taller and have more leaves, greater stem diameter and root volume than controls or plants treated with the other chemicals. The data obtained in this study are not conclusive, but indicated certain trends that more glasshouse trials and field trials would resolve. Results presented in this thesis indicate that a major shift has occurred in the status of soilborne fungi associated with roots and crowns of grapevines in nurseries in the Western Cape since the 1970s when Phytophthora and Pythium were predominant. The prevalence and role of soilborne fungi need to be determined so that new appropriate disease management strategies can be developed to limit losses in grapevine nurseries and ensure the sustainable production of healthy plants for the grapevine industry.
AFRIKAANSE OPSOMMING: 'N ONDERSOEK NA GRONDGEDRAAGDE SWAMME GEASSOSIEER MET WORTELS EN KRONE VAN WINGERD IN KWEKERYE Grondgedraagde siektes van wingerd is 'n komplekse probleem waaroor min inligting, beide plaaslik en internasionaal, beskikbaar is. Vorige navorsing in Suid-Afrika het aangedui dat swamme van die genera Phytophthora en Pythium die mees algemene en vernietigende grondgedraagde patogene in kwekerye en wingerde in die Wes-Kaap provinsie is. Die plaaslike wingerdbedryf brei huidiglik uit; nuwe kultivars, metodes en landbouchemikalieë word gebruik wat 'n invloed kan hê op grondgedraagde patogene. Gevolglik het dit noodsaaklik geword om die status van grondgedraagde patogene in wingerdkwekerye weer te bepaal, aangesien inligting in hierdie verband noodsaaklik is vir die ontwikkeling van siekte bestuurspraktyke vir die ontwikkelende plaaslike wingerdbedryf. Grondgedraagde swamgenera geassosieer met wortels en krone van terugsterwende wingerd in kwekerye is bepaal in opnames wat by drie verskillende wingerdkwekerye in die Wes-Kaap provinsie uitgevoer is. Cylindrocarpon, Fusarium, Pythium, en Rhizoctonia spp. is konstant vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, Cylindrocladiella spp. en Phytophthora cinnamomi is ongereeld vanuit siek wortels, krone en grond geïsoleer, terwyl Pythium spp. algemeen in meeste gronde voorgekom het. Resultate dui daarop dat die status van grondgedraagde swampatogene in wingerdkwekerye in die Wes- Kaap provinsie oor die laaste 30 jaar verander het. Die DNA filogenie en patogenisiteit van die isolate van Cylindrocladiella is bepaal. Vier spesies van Cylindrocladiella kom voor op wingerd in Suid-Afrika, naamlik C. lageniformis, C. parva, C. peruviana, sowel as 'n nuwe spesie, wat in hierdie studie as C. viticola aangedui is en wat deel is van die C. infestans spesie kompleks. Patogenisiteits proewe was onvoldoende om die patogeniese status van die swam me te bepaal. Tien Fusarium spp. is vanuit wortels en krone van terugsterwende wingerdplante in kwekery geïsoleer, naamlik F. acuminatum, F. anthophilum, F. chlamydosporum, F. equiseti, F. nygamai, F. oxysporum, F. proliferatum, F. scirpi, F. semitectum en F. solani. Die dominante spesies was F. oxysporum, gevolg deur F. proliferatum en F. solani. In pathogenisteitsproewe het F. oxysporum en F. solani gelei tot 'n betekenisvolle laer wortelvolume, droë massa van wortels, lengte en droë massa van nuwe groei en aantal blare, maar het die persentasie chlorotiese blare en graad van wortelvrot verhoog. Fusarium proliferatum het ook gelei tot 'n betekenisvolle afname in lengte en massa van nuwe groei, aantal blare en 'n verhoogde graad van wortelvrot in vergelyking met die kontrole behandelings. Dit wil voorkom asof Fusarium solani meer virulent is as F. oxysporum, gevolg deur F. proliferatum. Hierdie is die eerste aanmelding van F. oxysporum, F. proliferatum en F. solani as patogene van wingerd in Suid-Afrika, en die eerste aanmelding van F. proliferatum as 'n patogeen van wingerd in die wêreld. Phytophthora cinnamomi is konstant teen lae frekwensies vanuit terugsterwende wingerd in kwekerye geïsoleer, alhoewel dit in risosfeer gronde teenwoordig was. Dit is moontlik dat die ekstensiewe gebruik van chemikalieë teen donsskimmel in wingerdkwekerye die wingerdplante kan beskerm teen infeksie deur P. cinnamomi. Die effek van chemikalieë wat gebruik word teen donsskimmel op Phytophthora wortelverrotting van wingerd in kwekerye, is 'n glashuis geëvalueer. Die chemikalieë wat gestoets is, het vir die gemete parameters, tot baie min onderskeibare effek gelei relatief tot die kontrole plante, en daar is afgelei dat die inokulasie tegniek verbetering benodig. Plante wat met fosforiensuur behandel is, het egter geneig om langer te wees met meer blare, 'n groter stamdeursnee en wortelvolume as kontrole plante of plante behandel met ander chemikalieë. Data verkry vanuit die hierdie studie was onvoldoende, maar sekere neigings is aangedui wat deur verdere glashuis- en veldproewe verklaar sal word. Resultate wat in hierdie tesis weergegee is, het aangedui dat 'n algehele verskuiwing in die status van grondgedraagde swamme geassosieer met wortels en krone van wingerd in kwekerye vanaf die 1970s, toe Phytophthora en Pythium die dominante genera was, plaasgevind het. Die voorkoms en rol van grondgedraagde swamme moet bepaal word, sodat nuwe voldoende siektebestuurspraktyke ontwikkel kan word om verliese in wingerdkwekerye te beperk en sodoende die volhoubare produksie van gesonde plante vir die wingerdbedryf te verseker.

Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: South Africa is ranked eighth in the world as far as international wine production is concerned and in terms of area under bearing vines South Africa is ranked 12th. In 2011 the wine industry contributed R4 204.4 million to the South African economy in state revenue from wine products. The importance of viticulture to the economy of South Africa forces the industry to limit the effect of all disease causing pathogens in order to keep their competitive edge. Aster yellows (AY) phytoplasma 16SrI-B subgroup was reported for the first time in grapevine (Vitis vinifera L. (Vitaceae)) in South Africa in 2006. Worldwide phytoplasma diseases of grapevine cause serious damage ranging from lower yields to the death of vines. The lack of knowledge about the epidemiology of AY disease makes it difficult to determine the impact of the disease on the South African wine industry. The aim of this study was to conduct surveys in disease-affected vineyards in the Vredendal region to determine the incidence and spatial distribution of the disease in a variety of cultivars. The field surveys based on visual symptoms of AY disease were confirmed by polymerase chain reaction (PCR). A survey was also conducted in and around AY-infected vineyards in search of possible alternative host plants of the phytoplasma. Spatial distribution of AY-affected vines were analysed using the PATCHY spatial analysis package. A rapid decline of AY-affected Chardonnay eventually leading to the death of vines was observed, confirming the sensitivity of Chardonnay towards grapevine yellows infections. Symptomless AY infections occurred and AY could not be detected in all symptomatic vines, which indicate uneven distribution of AY in individual vines. Molecular analyses using PCR-RFLP showed that all vines sampled in the Vredendal vicinity contained AY phytoplasma only. No phytoplasmas were present in any weeds or other possible host plants tested. Although the mean yearly disease incidences of Chardonnay (29.95%) and Chenin blanc (16.64%) were higher than Pinotage (5.80%) over the four-year survey period, there was no statistically significant difference between the disease incidences of these three cultivars. The mean yearly disease incidence showed a trend over time and the disease incidence of the first year was significantly lower than that of the other years. Chardonnay showed a cumulative disease incidence of 37.77% at the end of the 4-year study which means that Chardonnay vineyards can be 100% AY infected in ten years’ time. Spatial distribution patterns of AY-infected vines were mostly non-random with clustering of disease affected vines along and across vine rows. With the exception of one vineyard, aggregation of AY-affected vines mostly occurred on the edge of vineyards adjacent to infected vineyards. This epidemiological study gives an indication of the sensitivity of the different cultivars towards AY, the tempo of spreading and the future impact of the disease on the South African wine industry. It also contributes valuable information towards the development of a management strategy for grapevine yellows disease in South African vineyards.
AFRIKAANSE OPSOMMING: Suid- Afrika is op agtste op die wêreld ranglys wat internasionale produksie van wyn aan betref, en in terme van oppervlakte onder wingerd, is Suid-Afrika 12de. In 2011 het die wynbedryf R4 204.4 miljoen tot die Suid-Afrikaanse ekonomie bygedra in staats inkomste uit wyn produkte. Die belangrikheid van wingerd tot die ekonomie van Suid-Afrika dwing die bedryf om die effek van alle siekteveroorsakende patogene te beperk, om sodoende hul kompeterende voordeel te behou. Aster vergeling (AY) fitoplasma 16SrI-B subgroep is vir die eerste keer in 2006 in wingerd (Vitis vinifera L. (Vitaceae)) in Suid-Afrika waargeneem. Fitoplasma siektes van wingerd veroorsaak wêreldwyd ernstige skade wat wissel van laer opbrengste tot die afsterf van wingerdstokke. Die gebrek aan kennis oor die epidemiologie van astervergeling siekte maak dit moeilik om die impak van die siekte op die Suid-Afrikaanse wynbedryf te bepaal. Die doel van hierdie studie was om ‘n opname te maak in siekte geaffekteerde wingerde in die Vredendal omgewing om sodoende siekte voorkoms en verspreidingspatrone van die siekte in 'n verskeidenheid van kultivars te bepaal. Die veld opnames, gebaseer op visuele simptome van aster vergeling siekte, was bevestig deur polimerase kettingreaksie (PKR). ‘n Opname is ook in en om aster vergeling geaffekteerde wingerde uitgevoer, op soek na moontlike alternatiewe gasheer plante van die fitoplasma. Verspreidingspatrone van astervergeling geaffekteerde wingerde is ontleed met behulp van die PATCHY ruimtelike analise pakket. 'n Vinnige agteruitgang van AY geaffekteerde Chardonnay, wat uiteindelik gelei het tot die afsterf van wingerde, is waargeneem, wat die sensitiwiteit van Chardonnay teenoor wingerdvergeling infeksie bevestig. Simptoomlose astervergeling fitoplasma infeksies kom voor en astervergeling fitoplasma kon nie opgespoor word in alle simptomatiese wingerdstokke nie, wat op oneweredige verspreiding van AY fitoplasma in individuele wingerdstokke dui. Molekulêre ontledings met behulp van PKR-RFLP het getoon dat alle wingerdstokke, wat in die Vredendal omgewing getoets is, slegs astervergeling fitoplasma bevat. Geen fitoplasmas was teenwoordig in enige onkruide of ander moontlike gasheer plante. Hoewel die gemiddelde jaarlikse siekte voorkoms van Chardonnay (29,95%) en Chenin Blanc (16,64%) oor die vier-jaar opname periode hoër was as dié van Pinotage (5,80%), was daar geen statisties beduidende verskil tussen die siekte voorkoms van hierdie drie kultivars nie. Die gemiddelde jaarlikse siekte voorkoms het 'n tendens oor tyd getoon, en die siekte voorkoms van die eerste jaar was betekenisvol laer as dié van die ander jare. Chardonnay het ‘n kumulatiewe siekte voorkoms van 37.77% aan die einde van die 4-jaar studie getoon, wat beteken dat Chardonnay wingerde binne 10 jaar 100% besmet kan wees met AY. Verspreidingspatrone van AY geaffekteerde wingerdstokke was meestal nie-ewekansig met bondeling van geaffekteerde wingerdstokke in en oor wingerd rye. Bondeling van AY geaffekteerde wingerdstokke het, met die uitsondering van een wingerd, meestal op die kant van wingerde aanliggend aan besmette wingerde, voorgekom. Die epidemiologiese studie gee 'n aanduiding van die sensitiwiteit van die verskillende kultivars ten opsigte van AY, die tempo van die verspreiding en die toekomstige impak van die siekte op die Suid-Afrikaanse wynbedryf. Dit dra ook waardevolle inligting by tot die ontwikkeling van 'n strategie vir die bestuur van wingerdvergeling siekte in Suid-Afrikaanse wingerde.

Thesis (MSc)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: Paecilomyces Ii/acinus, ras 251 (geregistreer in terme van wet 36 van 1947 as Suid-Afrika se eerste natuurlike nematisiede en kommersieel beskikbaar as PI Plus) is as biologiese beheer agent getoets by aartappels en in geïntegreerde beheer programme by sitrus en wingerd teen respektiewelik Me/oidogyne species, Ty/enchu/us semipenetrans en verskeie ektoparasitiese nematodes. Die swam toon belofte vir die beheer van hierdie nematodes en het terselfdertyd nie 'n nadelige effek op nie-teiken, voordelige organismes in die grond nie. Veral in kombinasie met chemiese middels, as deel van geïntegreerde programme, kan dit lei tot verminderde gebruik van hoogs toksiese middels en dus meer omgewingsvriendelike landboupraktyke. Biological control of plant parasitic nematodes on potatoes, citrus and grapevine with the fungus, Paecilomyces liIacinus. Paecilomyces liIacinus, race 251 (registered in terms of act 36 of 1947 as South Africa's first natural nematicide, commercially available as PI Plus) was tested as a biological control agent on potatoes and in integrated control programs on citrus and grapevine against Me/oidogyne species, Ty/enchu/us semipenetrans and various ectoparasitic nematodes respectively. The fungus shows promise for the control of these nematodes, without having a harmful effect on non-target, beneficial organisms in the soil. Especially in combination with chemical products, as part of integrated programs, this can lead to less use of highly toxic compounds and thus to more environmentally friendly agricultural practices.
AFRIKAANSE OPSOMMING: Sedert die ontdekking van die swam, Paeci/omyces Ii/acinus (Thom.) Samson as 'n effektiewe eierparasiet van Meloidogyne incognita acrita en Globodera pal/ida (Jatala et al., 1979) het verdere veldproewe in Peru tot die effektiewe beheer van M. incognita en Tylenchulus semipenetrans gelei. Na verskeie suksesse in Peru is die swam onder verskillende klimaat- en grondkondisies in verskeie ander lande beproef. Die sukses behaal in die Filippyne het gelei tot die kommersiële produksie van die swam onder die handelsnaam Biocon. Anders as met chemiese middels vind die werking van biologiese agente stadig oor tyd plaas. Biologiese beheer sal nie chemiese beheer sonder meer kan vervang nie. Dit behoort egter deel te vorm van geïntegreerde nematode bestuur. Inkorporering van die natuurlike organismes, die oordeelkundige gebruik van chemiese nematisiedes, moontlik in kombinasie met die biobeheer agente, weerstand, en ander kulturele praktyke moet ernstig oorweeg word as ons hoop om die steeds groeiende wêreldbevolking te voed (Jatala, 1986). Paecilomyces liIacinus, ras 251, Suid-Afrika se eerste geregistreerde natuurlike nematisiede, kommersieel beskikbaar as PI Plus, is in die Olifantsrivier besproeiingsgebied geëvalueer vir die bestuur van ekonomies belangrike plantparasitiese nematodes by aartappels, sitrus en wingerd. Hierdie gewasse is belangrike bedryfstakke van die streek en is onderhewig aan skade deur nematodes wat die opbrengs nadelig beïnvloed. Chemiese beheer bied slegs 'n korttermyn oplossing vir nematode probleme en skadelike getalle word in 'n kort tyd weer opgebou. Boonop lei dié hoogs toksiese middels tot agteruitgang van die omgewing en sy waterbronne. Die toenemende besorgdheid hieroor en die groot potensiaal van biologiese beheer agente (Jatala, 1986) was die hoofrede vir die werk waaroor hier gerapporteer word.

Bibliography: leaves 111-120. This study investigated various aspects of genetic resistance in fava beans to Ascochta blight (A. fabae) with the objective to facilitate an efficient breeding strategy for long-term control. Pathogenic variability of A. fabae was found to be high, as was genetic variation between resistant fava bean accessions. A number of alternative resistance genes to that of Ascot cultivar were identified.

Thesis (MSc)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), the vine mealybug, is of economic importance to the wine and table grape (viticulture) industries, as it characteristically causes more damage than other mealybug species. Mealybug infestations contaminate grapes with their waxy secretions, egg-sacs and honeydew production, on which sooty mould grows, resulting in the fruit being unmarketable. Many export grapes are rejected, prior to shipment, as a result of infestations and phytosanitary concerns with regard to mealybug infestations. They are also vectors for various plant viruses. Up to date, the most common method of mealybug control in South Africa has been the use of chemical insecticides. Unfortunately, mealybugs are difficult to control chemically, due to their secretive/hidden lifestyle, where chemicals do not reach them. Of great concern is the ability of mealybugs to rapidly build up resistance to insecticides as well as the negative environmental effects associated with chemical pesticide use. Alternatively, entomopathogenic nematodes (EPNs), belonging to the families Heterorhabditidae and Steinernematidae, have been identified as lethal insect pathogens and their insecticidal action, towards a variety of insect pests, has proven them to be valuable and effective biocontrol agents. Laboratory bio-assays, to determine the ability of eight different EPN isolates to infect and kill P. ficus, were conducted. Six of the isolates were indigenous species and the other two, Heterorhabditis bacteriophora and Steinernema feltiae, were produced in Germany and are commercially available in South Africa. Planococcus ficus was highly susceptible to two indigenous species, Heterorhabditis zealandica and Steinernema yirgalemense; responsible for 96% ± 2% and 65% ± 10% mealybug mortalities, respectively. Biological studies illustrated that both H. zealandica and S. yirgalemense are able to complete their life cycles within adult female P. ficus. There was no significant difference in the pathogenicity of commercially produced H. bacteriophora, recycled through an insect host, and those from the formulated commercial product. However, commercially produced S. feltiae individuals, that were recycled through an insect host, were statistically more effective than those that were not. The LC50 and LC90 values for H. zealandica, in the current study, were 19 and 82 infective juveniles (IJs) respectively, which were similar to the LC50 and LC90 values for S. yirgalemense at 13 and 80, respectively. The LC50 and LC90, for commercially available H. bacteriophora, were greater than they were for both H. zealandica and S. yirgalemense, with values of 36 and 555, respectively. Such results indicate that there is a definite positive relationship which exists between the concentration of IJs of all three nematode species, used for inoculation, and the percentage mortality of P. ficus. Sand column tests resulted in S. yirgalemense outperforming H. zealandica significantly, with average mortalities of 95% ± 1.4% and 82% ± 4.1%, respectively. As a result S. yirgalemense was chosen for further studies in the field. IJs of commercially produced H. bacteriophora and S. feltiae were exposed to imidacloprid in laboratory bioassays to determine the effect on survival and infectivity. This study established the fact that these two EPN species can be applied, in combination with imidacloprid, in an integrated pest management scheme. Soil application field trials at Welgevallen and Nietvoorbij, using S. yirgalemense and mealybugs in Eppendorf tubes, buried 15 cm in the soil, resulted in 50% ± 10% and 52% ± 12% mealybug mortalities, respectively, when applying IJs at a concentration of 80 IJs/cm2. No significant difference was found between mealybug mortalities as a result of the three IJ concentrations applied (20, 40 and 80 IJs/cm2) for both vineyards. Persistence trials indicated that after four months post application, Cydia pomonella larval mortalities showed no significant reduction in infectivity on the Welgevallen vineyard, while on the Nietvoorbij vineyard there were no larval mortalities. Tests to establish whether or not S. yirgalemense and H. zealandica produced ant deterrent factors, showed no significant differences between the number of intact cadavers for both nematode species and for cadavers that were either four or six days old. There is, however, indication that deterrent factors may be in action in cadavers that were used six days after inoculation with 60% and 49% remaining intact for H. zealandica and S. yirgalemense infected cadavers respectively. All freeze killed cadavers were consumed by Linepithema humile (Mayr) (Argentine ant). The effects of low temperatures on EPN movement and infectivity were tested for H. zealandica and S. yirgalemense in the laboratory. The mortality of P. ficus at 14˚C, as opposed to 25˚C, for S. yirgalemense and H. zealandica were found to be 9.1% ± 2.6% and 2.5% ± 1.2% respectively. Vertical sand column tests were also conducted at 14˚C for S. yirgalemense and H. zealandica, which produced low mealybug mortalities of 3.5% ± 2.4% and 8.5% ± 1.4% respectively. This illustrates the low infectivity of the two local species at low temperatures. Laboratory persistence trials, conducted over a period of four months with S. yirgalemense, showed steady persistence of 100%, while H. zealandica had a statistically significant decrease of codling moth mortalities to 44% ± 5%. A three armed olfactometer was designed to establish if S. yirgalemense responds and moves towards chemical cues in the soil. A significant greater average number of IJs moved towards the grape vine roots (246 ± 0.124 IJs), than to the mealybugs (133 ± 0.168 IJs) and to the control (4 ± 1.02 IJs). This demonstrates that S. yirgalemense does actively seek out its hosts and that volatile cues produced by damaged grape vine roots, are more attractive to the EPN than cues produced by P. ficus. This study illustrates that S. yirgalemense has great potential as a biopesticide for controlling P. ficus in the soil of South African grape vineyards. Emphasis was placed on soil application of S. yirgalemense in the field, which produced good results, while laboratory tests indicate the potential for further aerial field application trials on grape vines. As the EPNs are not negatively affected by the agrochemical imidacloprid, the simultaneous use and combined action of both agents will potentially provide the farmer with excellent control against P. ficus. Further field- and aerial application studies will complement the current study and hopefully provide positive results for the efficient control of P. ficus found on grape vines.
AFRIKAANSE OPSOMMING: Planococcus ficus (Signoret) (Hemiptera: Pseudococcidae), die wingerd witluis, is van groot ekonomiese belang vir die wyn en tafeldruif industrieë, aangesien dit kenmerkend meer skade veroorsaak as enige ander witluis spesies. Witluis infestasies besmet druiwe met hulle wasagtige afskeidings, eierssakke en heuningdou produksie, waarop swamme groei, wat tot gevolg het dat die druiwe onbemarkbaar is. Baie besendings druiwe, bestem vir uitvoer, word afgekeur weens witluis besmettings en ook as gevolg van fitosanitêre oorwegings. Hulle tree ook op as vektore van verskeie plantvirusse. Die mees algemene manier waarmee witluis in Suid-Afrika beheer word, is chemiese behandeling. Ongelukkig is witluis baie moeilik om chemies te beheer vanweë hulle verskuilde lewenswyse wat dit moeilik maak vir chemikalieë om hulle te bereik. Die vermoë van witluis om vinnig weerstand op te bou teen insekdoders, asook die negatiewe effek van chemiese middels op die omgewing, is kommerwekkend. Alternatiewelik, kan entomopatogeniese nematodes (EPNs) van die families Heterorhabditidae en Steinernematidae gebruik word vir die beheer van witluis. Hierdie nematodes is geïdentifiseer is as dodelike insek patogene, vir ʼn groot verskeidenheid van pes insekte en daar is bewys dat hulle as waardevolle en effektiewe biologiese beheer agente kan optree. Laboratorium biotoetse is gedoen om die vermoë van agt EPN isolate te evalueer om P. ficus te beheer. Ses van die EPN isolate is inheems, terwyl die ander twee, Heterorhabditis bacteriophora en Steinernema feltiae, in Duitsland produseer is en kommersieel beskikbaar is in Suid-Afrika. Planococcus ficus is hoogs vatbaar vir die twee inheemse EPN spesies, naamlik Heterorhabditis zealandica en Steinernema yirgalemense en hulle is verantwoordelik vir 96% ± 2% en 65% ± 10% van witluis mortaliteit. Biologiese studies het aangetoon dat beide H. zealandica en S. yirgalemense in staat is om hul lewensiklus te voltooi in volwasse wyfies van P. ficus. Daar is geen beduidende verskil gevind in die patogenisiteit van die geformuleerde kommersiële produk H. bacteriophora en dié wat in vivo geproduseer is nie. Daar is egter in die geval van S. feltiae, gevind dat die nematodes, wat in insekte produseer is, statisties beduidend meer effektief was, as dié wat kommersieel beskikbaar was. Die LC50 en die LC90 waardes van H. zealandica, in die huidige studie, was 19 en 82 infektiewe larwes (IJs), wat baie naby die LC50 en LC90 waarders van S. yirgalemense van 13 en 80 was. Die LC50 en LC90 vir die kommersieel beskikbare H. bacteriophora was groter as vir beide H. zealandica en S. yirgalemense, met waardes van 36 en 555 onderskeidelik. Hierdie resultate dui daarop dat daar ʼn positiewe verwantskap bestaan tussen die konsentrasie van die IJs van drie EPN spesies en die persentasie mortaliteit van P. ficus. Sand kolomtoetse dui daarop dat S. yirgalemense baie beter vaar as H. zealandica met gemiddelde mortaliteite van 95% ± 1.4% en 82% ± 4.1% onderskeidelik. Op grond van hierdie resultate is S. yirgalemense gebruik vir verdere veld studies. IJs van kommersieel geproduseerde H. bacteriophora en S. feltiae is in laboratorium biotoetse blootgestel aan imidacloprid om die effek op die oorlewing en infektiewe vermoë vas te stel. Hierdie studie het aangetoon dat die twee EPN spesies aangewend kan word saam met imidacloprid in ʼn geïntegreerde plaagbestuur opset. Grond aanwendings is in veld proewe by Welgevallen en Nietvoorbij gedoen deur gebruik te maak van S. yirgalemense en P. ficus volwasse wyfies in Eppendorf buisies, 15 cm in die grond begrawe, het albei 50% ± 10% en 52% ± 10% witluis mortaliteit, respektiewelik, tot gevolg gehad, met die toediening van nematodes teen ʼn konsentrasie van 80 IJs/cm2. Geen beduidende verskille is gevind tussen die witluismortaliteit en die resultate van die verskillende EPN konsentrasies (20, 40 en 80 IJs/cm2) wat op beide wingerde toegedien is nie. Oorlewings toetse het aangedui dat, drie maande na toediening, met Cydia pomonella as indikator, geen beduidende verskille in die infeksie potensiaal van die Welgevallen wingerd to gevolg gehad het nie, terwyl daar op die Nietvoorbij wingerd geen verdere larvale mortaliteit gevind is was nie. Toetse om vas te stel of S. yirgalemense en H. zealandica afkrikmiddels vir miere in besmette insek kadawers produseer het aangetoon dat daar geen beduidende verskil is tussen die getal kadawers wat intakt is vir beide EPN spesies en kadawers wat vier of ses dae oud is nie. Daar is egter aangetoon dat die afskrikmiddels wel ses dae na infeksie deur insek kadawers afgeskei word; aangesien 60% en 49% van die oorblywende kadawers nog volledig was toe dit geïnfekteer was met H. zealandica en S. yirgalemense, onderskeidelik. Al die insek kadawers, wat deur bevriesing doodgemaak is, was deur Linepithema humile (Mayr) (Argentynse mier) verorber.

Thesis (MScAgric)--Stellenbosch University, 2004.
ENGLISH ABSTRACT: Colonies of Planococcus ficus (Signoret) were reared from three different areas, Hex River Valley, Robertson and Stellenbosch. An insectary colony and a table grape colony from Nietvoorbij experimental farm were also included in the study. A range of concentrations of chlorpyrifos was applied topically to individuals from the different colonies. The Stellenbosch population had the lowest LDso, although it was not significantly different from that of the insectary and Robertson colonies. The Hex River Valley and table grape colonies had a significantly higher LDso than the Robertson, Stellenbosch and insectary colonies, although the relative tolerance was 1.5, which would probably not result in significant control failure in the field. However, this does indicate that there is potential for the development of resistance to chlorpyrifos in the vine mealybug in South Africa.
AFRIKAANSE OPSOMMING: Kolonies van Planococcus ficus (Signoret), is versamel en geteel uit drie verskillende areas, Hex.riviervallei, Robertson en Stellenbosch. 'n Bestaande insektarium kolonie van die Lanbou Navorsings Raad en 'n tafeldruif kolonie vanaf Nietvoorbij proefplaas is ook ingesluit in die studie. 'n Reeks konsentrasies van chlorpyrifos is topikaal aangewend aan individue van die verskillende kolonies. Die Stellenbosch populasie het die laagste LDso getoon alhoewel dit nie betekenisvol verskil het van die LDso van die insektarium - en Robertson kolonies nie. Die Hexriviervallei en tafeldruif kolonies se LDso was betekenisvol hoër as die Robertson, Stellenbosch and insektarium kolonies. Alhoewel die relatiewe weerstand 1.5 was, sal dit waarskynlik nie tot 'n aansienlike beheermislukking in die veld lei nie. Nogtans dui dit op die potensiaal vir moontlike ontwikkeling van weerstand teen chlorpyrifos in die wingerdwitluis.

Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: Grapevine leafroll-associated virus 3 (GLRaV-3) is the type member of the genus Ampelovirus in the family Closteroviridae and is considered to be the main contributing agent of grapevine leafroll disease (GLD) worldwide. A metagenomic sequencing study of a grapevine leafroll-diseased vineyard led to the discovery of a new variant of GLRaV-3 in South Africa. This new variant was most related to a New Zealand isolate, NZ-1. In this study, we sequenced two isolates, GH11 and GH30, of the new variant group of GLRaV-3. These isolates have less than 70% nucleotide (nt) identity to other known GLRaV-3 variants, indicating that they should be considered variants of a different strain of GLRaV-3. We propose that the GLRaV-3-like virus identified in this study be grouped together with NZ-1 and some Napa Valley isolates as Group VI of GLRaV-3. This study also provided further evidence that next-generation sequencing is an invaluable approach to identify novel viruses and variants, in that the draft sequence generated with bioinformatic tools in this study was 98% identical to the GH11 sequence generated using Sanger sequencing. The study further confirmed that the industry standard ELISA is still an effective GLRaV-3 diagnostic method and that it is able to detect all known variant groups of GLRaV-3. However, this assay is not able to differentiate between GLRaV-3 variant groups. In the current study therefore, a real-time RT-PCR was designed that is able to detect GLRaV-3 variant groups I, II, III and VI, using a single primer pair targeting the Hsp70h gene of GLRaV-3. If high-resolution melting (HRM) curve analysis is added to the real-time RT-PCR, it is possible to differentiate between variant groups based on three melting point intervals. The RT-PCR HRM assay provides a more sensitive and rapid tool to detect and differentiate between different GLRaV-3 variant groups. Finally, a multiplex RT-PCR was designed to differentiate between the variant groups present in South Africa. This multiplex RT-PCR offers a validation method for the RT-PCR HRM and provides an end-point PCR alternative for variant identification. In order to investigate the spread and impact of different GLRaV-3 variants in vineyards, sensitive diagnostic techniques are a necessity. The abovementioned tools will contribute to the understanding of the pathogenesis of GLD and aid epidemiological studies to investigate how these different GLRaV-3 variant groups are spreading, the association of specific GLRaV-3 variants to disease symptoms and the mealybug vector transmission efficiency for each GLRaV-3 variant.
AFRIKAANSE OPSOMMING: Grapevine leafroll-associated virus 3 (GLRaV-3) is ’n lid van die genus Ampelovirus in die familie Closteroviridae en word beskou as die hoof bydraende faktor van wingerd-rolbladsiekte wêreldwyd. ’n Metagenomiese studie het bewys dat daar ’n nuwe variant van GLRaV-3 bestaan wat nog nie voorheen in Suid Afrika opgespoor kon word met die huidige opsporingsmetodes nie. Hierdie nuwe variant was naaste verwant aan ’n Nieu-Seelandse isolaat, NZ-1. In hierdie studie is die genoomvolgorde van twee isolate, GH11 en GH30, van hierdie nuwe GLRaV-3 variant groep bepaal. Hierdie twee isolate was minder as 70% identies aan ander GLRaV-3 variante, wat daarop dui dat hulle as variante van ’n nuwe virus-ras beskou behoort te word. Ons beveel aan dat hierdie GLRaV-3-verwante virus geklassifiseer word saam met die NZ-1 isolaat en ander isolate uit Kalifornië, as groep VI van GLRaV-3. Hierdie studie het ook verdere bewyse verskaf dat volgende-generasie volgordebepalingstegnologie ’n waardevolle benadering is om nuwe virusse en variante te identifiseer, deurdat die huidige studie gewys het dat die voorlopige volgorde, wat gegenereer is deur bioinformatika-instrumente, 98% identies was aan die GH11 volgorde wat met Sanger volgordebepaling verkry was. Hierdie studie het ook gevind dat die industrie-standaard ELISA, nog steeds ’n effektiewe GLRaV-3 diagnostiese metode is en wel infeksies, veroorsaak deur al die variant-groepe, sal kan identifiseer. Die ELISA toets is egter nie in staat om te onderskei tussen GLRaV-3 variant-groepe nie. In hierdie studie is ’n variant-identifiseerbare in-tyd tru-transkripsie polimerase ketting reaksie (PKR) ontwerp wat GLRaV-3 variant-groepe I, II, III en VI kan identifiseer deur middel van ’n enkele inleier-stel wat die GLRaV-3 Hsp70h-geen teiken. As hoë-resolusie smeltingskurwe-analise bygevoeg word by die in-tyd tru-transkripsie PKR, is dit moontlik om te onderskei tussen variant-groepe op grond van drie smeltingspunt intervalle. Die tru-transkripsie hoë-resolusie smeltingskurwe-toets verskaf meer sensitiewe en geoutomatiseerde metodes om GLRaV-3 variant-groepe te identifiseer en te onderskei. ’n Veelvuldige tru-transkripsie PKR is ook ontwerp om tussen variante wat tans in Suid-Afrika aangetref word, te onderskei en te dien as ’n valideringsmetode vir die in-tyd tru-transkripsie hoë-resolusie smeltingskurwe-toets. Sensitiewe en akkurate toetse, soos bogenoemde, is noodsaaklik vir die bestudering van die verspreiding en impak van die verskillende GLRaV-3 variante in wingerd. Hierdie metodes kan gebruik word om kennis ten opsigte van rolblad patogenese te verbreed en om by te dra tot epidemiologiese studies wat ondersoek hoe hierdie variant-groepe versprei, of daar ’n assosiasie bestaan tussen ’n spesifieke variant en siekte-simptome en of daar ’n verskil is in die witluisvektor oordragseffektiwitiet vir elke GLRaV-3 variant.

Thesis (MSc)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: Grapevine trunk diseases are caused by invasive pathogens that are responsible for the slow decline of vines. In particular, Eutypa dieback of grapevine has had a devastating impact on vineyards worldwide, reducing growth and yield, eventually killing the grapevine. The causal organism of Eutypa dieback was first described as Eutypa armeniacae Hansf. & Carter, the pathogen that causes dieback of apricots, but since 1987 this species has been considered a synonym of Eutypa lata (Pers.:Fr.) Tul & C. Tul (anamorph Libertella blepharis A. L. Smith). Recently, it was proposed that at least two species that are capable of infecting grapevines are responsible for Eutypa dieback. Consequently, the molecular identification and characterisation of Eutypa dieback was used to delineate the species occurring on infected grapevines in South Africa. This involved the molecular analyses of three molecular markers, namely, the internal transcribed spacer (ITS) and large subunit (LSU) regions of the ribosomal DNA operon, and the -tubulin gene. The results obtained revealed the presence of a second species, namely, Eutypa leptoplaca (Mont.) Rappaz, that occurred together with E. lata on infected grapevines. Also co-habiting with these pathogens were related fungi form the Diatrypaceae family, Cryptovalsa ampelina (Nitschke) Fuckel and Eutypella vitis (Schwein.) Ellis & Everhart. Pathogenicity tests conducted on isolates representing C. ampelina, E. lata, E. leptoplaca, and E. vitis revealed that all were pathogenic to grapevine. Several species of Botryosphaeriaceae that commonly invade the woody tissue of grapevines are also pathogenic to grapevine. The symptoms in grapevine commonly associated with Botryosphaeriaceae are easily confused with the symptoms produced by Eutypa dieback which prompted the need for the development of a detection method that can correctly identify the presence of multiple pathogens. A reverse dot blot hybridisation (RDBH) method was subsequently applied to provide a rapid, accurate and reliable means of detecting the Eutypa species involved in the Eutypa disease complex, as well as those species of Botryosphaeriaceae known to cause disease in grapevines. The method involved the use of multiplex PCR to simultaneously amplify and label the regions of DNA that are used as pathogen specific probes. Consequently, membrane immobilised species-specific oligonucleotides synthesised from the ITS, - tubulin and LSU molecular data were evaluated during the application of this diagnostic method to detect Eutypa species. It was found that the species-specific oligonucleotides, designed from ITS sequence data, could consistently detect E. lata and E. leptoplaca. The application of the RDBH method for the detection of these Eutypa species, based on -tubulin and LSU sequence data, however, proved to be unsuccessful. Subsequently, a RDBH method, utilising species-specific oligonucleotides designed from elongation factor-1α sequence data, was successfully applied for the detection of Botyrosphaeria dothidea (Moug.:Fr.) Ces. & De Not., Neofusicoccum luteum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers, A.J.L. Phillips and Neofusicoccum ribis (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips. The method, however, was unsuccessful for the detection of Diplodia seriata De Not. In addition to the above-mentioned shortcomings, the RDBH was not amenable to the detection of pathogens directly from field or environmental samples, but required preparation of DNA from pure cultures. The method, however, allows for the identification of multiple pathogens in a single assay. As DNA extraction methods are amended, improved and honed to obtain DNA from environmental samples, so would it increase the usefulness of RDBH.
AFRIKAANSE OPSOMMING: Wingerd stamsiektes word veroorsaak deur patogene wat die vermoë het om wingerdplante te infekteer en dan stadige agteruitgang van dié wingerde te veroorsaak. Veral Eutypa terugsterwing het ‘n vernietigende effek op wingerde wêreldwyd deurdat dit groeikrag en oesmassa verlaag, maar ook omdat dit uiteindelik wingerdstokke kan dood. Die veroorsakende organisme is aanvanklik as Eutypa armeniacae Hansf. & Carter beskryf, die patogeen wat terugsterf by appelkose veroorsaak, maar sedert 1987 word hierdie spesies beskou as ‘n sinoniem van Eutypa lata (Pers.:Fr.) Tul & C. Tul (anamorph Libertella blepharis A. L. Smith). Dit is egter onlangs voorgestel dat ten minste twee spesies die vermoë het om wingerd te infekteer om Eutypa terugsterwing te veroorsaak. Gevolglik is molekulêre identifikasie- en karakteriseringstudies geloods om te bepaal watter spesies Eutypa terugsterwing in Suid-Afrikaanse wingerde veroorsaak. Dit het die molekulêre analise van drie molekulêre merkers behels, naamlik die interne getranskribeerde spasiëerderarea (“ITS”), die groot ribosomale subeenheid (“LSU rDNA”) en β-tubilien geen. Resultate van die filogenetiese analise dui daarop dat ’n tweede spesies, naamlik Eutypa leptoplaca (Mont.) Rappaz, saam met E. lata in geïnfekteerde plante voorkom. Saam met bogenoemde twee spesies het daar ook verwante spesies van die Diatrypaceae familie voorgekom, naamlik Cryptovalsa ampelina (Nitschke) Fuckel en Eutypella vitis (Schwein.) Ellis & Everhart. Patogenisiteitstudies wat uitgevoer is met verteenwoordigende isolate van C. ampelina, E. lata, E. leptoplaca, en E. vitis dui daarop dat almal patogene van wingerd is. Verskeie Botryosphaeriaceae spesies wat gereeld in houtagtige wingerdweefsel aangetref word, is ook patogene van wingerd. Interne simptome wat algemeen met Botryosphaeriaceae infeksies geassosieer word, kan baie maklik met dié van Eutypa terugsterwing verwar word en dit het die nood laat ontstaan om ‘n opsporingsmetode te ontwikkel wat akkuraat genoeg is om tussen veelvoudige infeksies te onderskei. ’n Omgekeerde-stippelklad-hibridisasie (OSH) metode is gevolglik aangewend om Eutypa spesies betrokke in die Eutypa-siektekompleks op ‘n vinnige, akkurate en betroubare manier op te spoor, sowel as die Botryosphaeriaceae species wat bekend is as patogene van wingerd. Die metode behels ’n saamgestelde PKR vir die vermeerdering en merk van DNS areas wat gebruik word as patogeen spesifieke peilers. Spesies-spesifieke oligonukleotiede ontwikkel vanaf die ITS, -tubilien en LSU molekulêre data is op ‘n membraan vasgeheg en gebruik om ’n diagnostiese toets te ontwikkel vir Eutypa species. Merkers ontwikkel vanaf die ITS kon E. lata and E. leptoplaca konsekwent opspoor. Die opspoor van Eutypa spesies met merkers vanaf die -tubulien en LSU gene met OSH was onsuksesvol. Die OSH metode met merkers vanaf die verlengingsfaktor-1α kon susksesvol gebruik word om Botyrosphaeria dothidea (Moug.:Fr.) Ces. & De Not., Neofusicoccum luteum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers, A.J.L. Phillips and Neofusicoccum ribis (Slippers, Crous & M.J. Wingf.) Crous, Slippers & A.J.L. Phillips op te spoor. Dié metode kon egter nie Diplodia seriata De Not. opspoor nie. Bykomend tot bogenoemde tekortkominge, kon die omgekeerde-stippelklad-hibridisasie metode ook nie aangepas word om patogene direk vanuit plantmateriaal op te spoor nie en word DNS afkomstig vanaf suiwer kulture benodig. Dié metode laat egter identifikasie van verskeie patogene in ‘n enkele toets toe. Soos DNS ekstraksie metodes aangepas, verbeter en verfyn word om DNS vanuit plantmateriaal te verkry, sal die bruikbaarheid van die omgekeerde stippelklad hibridisasie metode ook verbeter.

Thesis (MScAgric)--University of Stellenbosch, 2002.
ENGLISH ABSTRACT: Botrytis bunch rot of grape is caused by Botrytis cinerea Pers. :Fr. Conidia of the pathogen, which is dispersed by wind, water droplets and by insects, can penetrate the intact grape berry cuticle, but disease expression occurs only under predisposing conditions. Since relatively high infection rates often occur in vineyards, predisposing factors must play a fundamental role in primary infection and subsequent disease occurrence. Insects can play a very important role in this regard by depositing inocula at wound sites during feeding and by providing fresh wounds during their oviposition and feeding activities. The aim of this study was (i) to determine the potential of the Mediterranean fruit fly to transfer B. cinerea and other bunch and fruit rot fungi in natura, (ii) to investigate the transport, deposition and subsequent disease expression on grape berries in vitro, and (iii) to investigate fruit fly activities and the nature of deposited conidia and mycelia of B. cinerea by aid of digital photography and epifluorescence microscopy, respectively. Two Sensus fruit fly traps containing the para-pheromone, Capilure, were installed in orchards and five neighboring vineyards on four farms in the Stellenbosch region. Ceratitis fruit flies were collected weekly, identified and counted to determine the fluctuations in fruit fly population. Following field collection, the fruit flies were plated on Kerssies' B. cinerea selective medium and the number of flies yielding the pathogen was recorded. Two fruit fly species, C. capitata and C. rosa, were captured during the study period. Ceratitis rosa numbers comprised only 1% of the total number of fruit flies captured. Ceratitis capitata numbers, and the percentage B. cinerea contaminated flies generally increased after harvest in the different orchards and vineyards. Following harvest, the percentage flies yielding B. cinerea was higher in vineyards compared to orchards. Furthermore, in each vineyard an increase in percentage B. cinerea contaminated fruit flies was preceded by a corresponding increase in its neighboring orchard. The levels of both Penicillium and Alternaria contaminated fruit flies stayed high throughout the investigation period, especially after harvest of the orchard cultivars. Low incidence of Aspergillus, Mucor and Rhizopus spp. were recorded on C. capitata. These findings suggest that the Mediterranean fruit fly may play an important role in the dispersal of inocula of fungi associated with postharvest decay from early-maturing stone fruit orchards to mid- and late-maturing wine grape vineyards, and in disease induction under conditions unfavourable for natural infection. Three experiments were conducted to determine the potential of fruit flies in provoking B. cinerea decay. In the first experiment, transport of conidia and disease expression were investigated on rachis segments bearing unwounded berries only. In the second experiment, the effect of wounding on disease expression was investigated. In the third experiment, the effect of inoculum type (mycelia and conidia) on transportation and disease expression was investigated on rachis segments bearing unwounded berries, and on segments with wounded berries. The table grape cultivar, Dauphine, and the wine grape cultivar, Shiraz, were used at véraison, two weeks before harvest and harvest, and the transport studies were conducted in ethanol-disinfected perspex cages. Disease expression was studied in dry (~56% RH), ethanol-disinfected perspex chambers incubated at 22°C. The isolations from berries revealed that the flies deposited, without preference, high amounts of B. cinerea at various positions on the grape berry's surface. The freezing studies showed that the deposited conidia germinated and penetrated the berry skin at various positions. However, B. cinerea developed more often at the pedicel end than on the cheek or style end, which indicated a peculiar interaction between B. cinerea, the fruit fly and host tissue at this part of the berry. This phenomenon was substantiated by the finding that B. cinerea also developed more often at the pedicel end of berries that were not frozen. Further evidence for this interaction was found on intact berries exposed to flies that carried mycelia after feeding on berries without sporulating colonies of the pathogen, but showing symptoms of slippery skin. Significantly more decay developed on wounded berries compared to the unwounded berries and more so at the wound site. In addition, female fruit flies were responsible for significantly more decay development than male fruit flies. The study thus proved that the Mediterranean fruit fly can promote B. cinerea disease development under conditions unfavorable to natural infection. The activities of the Mediterranean fruit fly, Ceratitis capitata, on grape berries were monitored by aid of digital photography. In addition, the deposition of conidia and mycelia of Botrytis cinerea at three sites (pedicel end, cheek and style end) on the grape berry, germination of the fungal structures after dry (±56% RH) and moist (±93% RH) incubation and wounds inflicted during ovipositioning were examined with an epifluorescence microscope. The observations revealed that the fruit fly's activities were generally restricted to the grape berry. They visited the grape berry cheek more often, but visitations to the pedicel end of berries increased substantially from véraison to harvest, indicating the possibility of nutrient leakages at this site. Microscopy revealed that the flies deposited conidia singular, in feeding packages and in faecal excrements on the berry surface. The conidia in feeding packages were ensheathed by salivical fluids and occurred in clusters of 10 to 50 conidia. An average of 60% of the conidia in feeding packages germinated under dry conditions (±56% RH). Conidia that passed through the intestinal tract of the fruit fly and that were deposited in faecal excrements were deformed and low in viability. These conidia did not occur in cluster format, but were proportionally spread with the faeces on the surface of the grape berry. Conidia that were deposited singular and in faecal excrements did not germinate unless incubated under moist conditions (± 93% RH). Wounds inflicted by female fruit flies during ovipositioning were most frequently observed on the cheek. This predisposition to B. cinerea infection of grape berries by the activities of fruit flies, suggested an important role for the flies in the initiation of Botrytis bunch rot epidemics in vineyards.
AFRIKAANSE OPSOMMING: DIE ROL VAN DIE MEDITERREENSE VRUGTEVLIEG, CERATITIS CAPITATA, IN BOTRYTIS CINEREA TROSVERROTTING VAN DRUIWE Botrytis-trosverrotting van druiwe word deur Botrytis cinerea Pers. :Fr. veroorsaak. Konidia van die patogeen wat deur wind, waterdruppels en insekte versprei word, kan die intakte druiweskil binnedring, maar siekte-uitdrukking vind slegs onder spesiale omstandighede plaas. Aangesien relatief hoë infeksie vlakke algemeen in wingerde voorkom, moet predisponerende faktore 'n fundamentele rol in die primêre infeksie, en die daaruit voortspruitende siektetoestand speel. Insekte kan 'n baie belangrike bydrae lewer deur inokuia tydens voeding by wonde te deponeer. Nuwe wonde kan ook tydens oviposisionering en voeding ontstaan. Die doel van hierdie studie was om (i) die potensiaal van die Mediterreense vrugtevlieg om B. cinerea en ander tros- en vrugverrottingswamme in natura oor te dra, te bepaal; om (ii) die verspreiding, deponering en daaropvolgende siekteuitdrukking op druiwekorrels in vitro te ondersoek; en om (iii) die aktiwiteite en aard van die gedeponeerde konidia en miselia met behulp van digitale fotografie sowel as epifluoressensiemikroskopie waar te neem. Twee Sensus-vrugtelokvalle met die paraferomoon, Capilure, IS In vrugteboorde en aangrensende wingerde in die Stellenbosch-omgewing aangebring. Ceratitis-vrugtevlieë is weekliks versamel, geïdentifiseer en getel om fluktuasies in die vrugtevliegpopulasie te bepaal. Na die veldversameling is die vrugtevlieë op Kerssies se B. cinerea-selektiewe medium uitgeplaat. Gedurende die studie is twee spesies vrugtevlieë, C. capitata en C. rosa, gevang. Na oesstyd het die aantal Ceratitis-vrugtevlieë en die persentasie vrugtevlieë, besmet met B. cinerea, in die verskillende boorde en wingerde toegeneem. Na oestyd was die persentasie vrugtevlieë wat B. cinerea gedra het, hoër in die wingerde as in die boorde. Elke toename in die persentasie B. cinerea-besmette vrugtevlieë in 'n wingerd is voorafgegaan deur 'n ooreenkomstige toename in die aangrensende vrugteboord. Die aantal vrugtevlieë besmet met Penicillium en Alternaria spp. het tydens die navorsingstydperk deurgaans hoog gebly, veral nadat die vrugteboord-kultivars geoes is. Die voorkoms van Aspergillus-, Mucor- en Rhizopus spp. op Ceratitis-vrugtevlieë was deurgaans laag. Hierdie bevinding wys daarop dat vrugtevlieë 'n belangrike rol speel in die verspreiding van swarninokula, wat met na-oes verrotting geassosieer word, van vroegrypwordende steenvrugteboorde na mid- en laatrypwordende wyndruifwingerde. Drie eksperimente is in vitro onderneem om vrugtevlieë se potensiaal om B. cinereaverrotting te veroorsaak te bepaal. In die eerste eksperiment is ragi met slegs ongewonde korrels gebruik om die oordrag van konidia en siekte-ontwikkeling te ondersoek. In die tweede eksperiment is die effek van verwonding op siekte-ontwikkeling ondersoek. In die derde eksperiment is die effek van inokulumtipe (miselia en konidia) op verspreiding en siekte-ontwikkeling ondersoek deur ragis-segmente met gewonde korrels sowel as ragissegmente met ongeskonde korrels te gebruik. Die tafeldruif-kultivar Dauphine en die wyndruif-kultivar Shiraz, by kleurbreuk, twee weke voor oes en by oestyd, is in die eksperimente gebruik. Die oordragstudies is in etanol-ontsmette perspex-hokke uitgevoer. Siekte-ontwikkeling is bestudeer in droeë (±56% RH), etanol-ontsmette perspex-kamers en geinkubeer by 22°C. By ondersoek is gevind dat vlieë, sonder voorkeur, groot hoeveelhede B. cinerea op verskeie dele op die druiwekorrel-oppervlak deponeer. Bevriesingstudies het aangetoon dat die gedeponeerde konidia op verskeie dele van die korrelontkiem en die skil binnedring. Botrytis cinerea het egter meer dikwels by die korrelsteelkant as by die stempelkant, of op die wang, ontwikkel. Hierdie bevinding het 'n eiesoortige interaksie tussen B. cinerea, die vrugtevlieg en gasheerweefsel by die korrelsteelkant van die korrel aangetoon. Die verskynsel is gestaaf deur die bevinding dat B. cinerea ook meer dikwels by die korrelsteelkant van die korrels wat nie gevries is nie, ontwikkel het. Verdere bewys van hierdie interaksie is gevind by ongeskonde korrels wat aan die vlieë wat miselia gedra het blootgestel is. Die siekte het beduidend meer dikwels op gewonde as ongewonde korrels en verder aansienlik meer dikwels op die wondoppervlakte ontwikkel. Dit was ook duidelik dat vroulike vrugtevlieë baie meer vir verrotting verantwoordelik was as manlike vrugtevlieë. Die studie bewys dus dat Mediterreense vrugtevlieë die ontwikkeling van B. cinerea kan bevorder in omstandighede wat ongunstig is vir natuurlike infeksie. Die aktiwiteite van die Mediterreense vrugtevlieg C. capitata op die druiwekorrels is met behulp van digitale fotografie waargeneem. Verder is die deponering van konidia en miselia van B. cinerea op die verskillende dele (korrelsteelkant, wang en stempelkant) van die korrel, ontkieming van die swamstrukture na droeë (±56% RH) en nat (±93% RH) inkubasie en wonde wat tydens oviposisionering veroorsaak is, met epifluoressensie-mikroskopie ondersoek. Die waarnemings het onthul dat die vrugtevlieg se aktiwiteite gewoonlik tot die druiwekorrel beperk is. Hulle het korrelwange meer dikwels besoek. Besoek aan die korrelsteelkant het aansienlik toegeneem van kleurbreuk tot oestyd, wat op die moontlikheid van voedingstof-lekkasie by die deel aandui. Mikroskoopstudies het aangedui dat vlieë konidia enkel, in voedingspakkies en in fekale uitskeidings op die korreloppervlakte deponeer. Die konidia in die voedingspakkies is deur speekselvloeistof omhul en het in groepe van 10 tot 50 konidia voorgekom. Gemiddeld 60% van die konidia in voedingspakkies het in droeë omstandighede (±56% RH) ontkiem. Konidia wat deur die spysverteringskanaal van die vrugtevlieg gegaan het en in die fekale ekskresie gedeponeer is, was misvorm en het lae lewensvatbaarheid gehad. Laasgenoemde konidia was nie in groepe gedeponeer nie, maar is proporsioneel met die feces op die oppervlak van die druiwekorrel versprei. Konidia wat enkel en in feces gedeponeer is, het nie ontkiem nie, tensy toestande vogtig (±56% RH) was. Wonde wat deur die vroulike vrugtevlieë tydens oviposisionering veroorsaak is, is meer dikwels op die wang van die korrelopgemerk. Hierdie predisposisie van druiwekorrels tot B. cinerea-infeksie, meegebring deur die aktiwiteit van die vrugtevlieg, dui daarop dat die rol wat die vrugtevlieg in die inisiëring van Botrytis trosverrottingepidemies in wingerde speel, van beduidende belang is.

Thesis (MScAgric (Plant Pathology))--Stellenbosch University, 2009.
ENGLISH ABSTRACT: Sufficient fungicide deposition on the target site is an essential requirement for effective chemical management of fruit- and foliar diseases such as grey mould of grapevines. Control failure is often attributed to insufficient quantitative deposition on susceptible grapevine tissue. However, in high disease pressure situations control failure might also be attributed to poor qualitative deposition. The primary objective of spray technology is to optimise deposition, of which the plant surface is a critical component in the spray application process, specifically in the retention of spray droplets. Adjuvant technology is reported to improve the wettability and spread of droplets by surface-acting-agents on the target surface and thereby improve deposition and retention of the fungicide active ingredient. However, this relatively new spray technology on viticulture and horticultural crops, and possible effects of adjuvants on epicuticular wax affecting plant disease development, needs to be investigated. Moreover, the development of useful prescriptions for adjuvants by determining water volumes and adjuvant dosages is required for different pesticide tank mixes. The aims of this study were, firstly to determine the effect of selected adjuvants on quantitative and qualitative spray deposition on grapevine leaves and subsequent biological efficacy of a fungicide, and secondly to evaluate selected adjuvants under field conditions and determine the effects of adjuvant dosage and spray volume on deposition. Leaves were sprayed under similar laboratory conditions to pre-run-off with 1 mL of a mixture of fenhexamid (Teldor® 500 SC, Bayer) at recommended dose, a fluorescent pigment (SARDI Fluorescent Pigment, 400 g/L EC; South Australian Research and Development Institute) at 0.2 L/100 L, as well as 15 selected commercial adjuvants to manipulate the deposition quality of a given quantity of deposited spray. Spray deposition on leaves was illuminated under black light (UV-A light in the 365 nm region) and visualised under a stereo microscope (Nikon SMZ800) at 10× magnification. Photos of sprayed leaf surfaces were taken with a digital camera (Nikon DMX 1200). Digital images were quantitatively and qualitatively analysed with Image-Pro Discovery version 6.2 for Windows (Media Cybernetics) software, to determine spray deposition. The sprayed leaves were inoculated with 5 mg dry airborne conidia of Botrytis cinerea in a spore settling tower and incubated for 24 h at high relative humidity (≥ 93%). Leaf discs were isolated onto Petri dishes with paraquat-amended water agar and rated 11 days later for development of B. cinerea from isolated leaf discs. B. cinerea incidence on the upper and lower surfaces of water sprayed leaves averaged 90.4% and 95.8%, respectively. Despite full spray cover of leaves, applications with fenhexamid alone did not completely prevent infection and resulted in 34.6% and 40.8% B. cinerea incidence on the upper and lower surfaces of leaves, respectively. Through the addition of certain adjuvants, B. cinerea incidences were significantly lower (2.9-17.1% and 10.0-30.8%, respectively), while some adjuvants did not differ from the fungicide-only treatment, even though they might have improved spray deposition. The effects of Hydrosilicote and Solitaire alone and in combination with fenhexamid on germinating Botrytis conidia on leaf surfaces were studied in a histopathology study using epifluorescence microscopy. Distinct differences were observed in conidium mortality, germination and germ tube lengths between adjuvants alone and in combination with the fungicide, which might be attributed to indirect effects of the adjuvant mode of action on B. cinerea. The laboratory study clearly demonstrated the potential of adjuvants to improve the bio-efficacy of a fungicide directly through improved deposition on grapevine leaf surfaces. For the vineyard evaluations, the same fluorometry, photomicrography and digital image analysis protocol were used to assess quantitative and qualitative spray deposits under varying adjuvant dosage and volume applications. The Furness visual droplet-rating technique was initially included to determine optimum spray volume with a STIHL SR400 motorised backpack mistblower by assessment of pigment deposition on Chardonnay leaves under illuminated black light. Both assessment protocols showed that quantitative spray deposition increased with increasing spray volume applications of 40 L/ha to 750 L/ha, but decreased at 900 L/ha, possibly due to run-off. The addition of selected adjuvants at recommended dosage and at 600 L/ha demonstrated the potential of adjuvants to increase quantitative and qualitative deposition significantly on upper and lower leaf surfaces. Agral 90, BB5, Nu-film-P, and Solitaire significantly improved deposition on upper and lower leaf surfaces compared with the fenhexamid only and water sprayed control. Break-thru S 240 and Villa 51 did not improve quantitative deposition, although remarkably better qualitative deposition was obtained. An adjuvant dosage effect (within the registered dosage range) was evident, especially those retained on the upper leaf surfaces. Agral 90 and Nu-film-P affected significant improvement of spray deposition at the higher, but not at the lower dosage tested. Solitaire improved deposition at the lower dosage tested, whereas reduced deposition at the higher dosage was attributed to excessive spray run-off. No significant improvement of spray deposition was observed for both dosages tested with Villa 51. Spray mixtures with adjuvants Agral 90 and Solitaire yielded similar deposition values at 600 L/ha compared with the fenhexamid only control at 900 L/ha, but reduced deposition at the higher spray volume, possibly due to spray run-off. This study clearly demonstrated the potential of adjuvants to improve quantitative and qualitative deposition, but highlights the necessity to match adjuvant dosages and application volumes on the spray target to achieve maximum spray deposition.
AFRIKAANSE OPSOMMING: Effektiewe beheer van vrug- en blaarsiektes soos vaalvrot op wingerde benodig voldoende deponering van die swamdoder op die teikenoppervlak. Verlies aan beheer word gewoonlik aan onvoldoende kwantitatiewe deponering op vatbare wingerddele toegeskryf. Onder ‟n hoë siektedruk kan mislukte beheer ook moontlik toegeskryf word aan swak kwalitatiewe deponering. Die primêre doelwit van spuittegnologie is om deponering te optimaliseer met die plantoppervlak as ‟n belangrike komponent in die spuittoedieningsproses, spesifiek in die retensie van spuitdruppels. Byvoemiddel tegnologie het bewys dat oppervlak-aktiewe-agente verbeterde benatting en verspreiding van druppels op die teiken oppervlakte tot gevolg kan hê, en verder ook die deponering en retensie van die aktiewe fungisied bestanddele kan verbeter. Hierdie relatiewe nuwe spuittegnologie op wingerd- en hortologiese verbouing, asook die moontlike effekte van byvoegmiddels op epikutikulêre waks om siekte ontwikkeling te beïnvloed, moet ondersoek word. Verder word nuttige aanbevelings benodig vir byvoegmiddel toedienings by verskillende spuitvolumes en dosisse van die betrokke spuitmengsel. Die doelwit van hierdie studie was, eerstens om die effek van sekere byvoegmiddels op kwantitatiewe en kwalitatiewe spuitbedekking van wingerdblare te bepaal en dan te vergelyk met die biologiese effektiwiteit van ‟n fungisied, en tweedens om van die byvoegmiddels onder veldtoestande te evalueer, asook die effek van byvoegmiddel dosisse en spuitvolumes te bepaal. Blare is onder dieselfde laboratorium toestande tot net voor-afloop met 1 mL van ‟n spuitmengsel, bestaande uit fenhexamied (Teldor® 500 SC, Bayer) teen die aanbevole dosis, ‟n fluoreserende pigment (400 g/L EC; Suid Australiese Navorsing en Ontwikkeling Instituut) teen 0.2 L/100 L, sowel as 15 geselekteerde kommersiële byvoegmiddels gespuit om die kwalitatiewe deponering, vir ‟n gegewe kwantiteit van spuitdeponering, te manipuleer. Die fluoreserende pigment is op die blaaroppervlak belig met ‟n swart lig (UV-A ligbron in die 365 nm golflengte) en deponering is onder ‟n stereo mikroskoop (Nikon SMZ800) teen 10× vergroting waargeneem. Die gespuite blaaroppervlaktes is op die manier met ‟n digitale kamera afgeneem (Nikon DMX 1200), waarna die digitale foto‟s kwantitatief en kwalitatief deur die gebruik van „Image-Pro Discovery version 6.2 for Windows (Media Cybernetics)‟ sagteware geanaliseer is om spuitbedekking te bepaal. Na elke blaarspuit is die blare met 5 mg droë konidia van B. cinerea in ‟n inokulasietoring geïnokuleer en daarna vir 24 h onder hoë relatiewe humiditeit (≥ 93%) geïnkubeer. ‟n Aantal skyfies vanuit elke blaar is op Petri bakkies met paraquat medium geïsoleer en 11 dae later is die persentasie van B. cinerea ontkieming bepaal. Die gemiddelde voorkoms van B. cinerea op die blare wat slegs met water gespuit is, was 90.4% op die boonste en 95.8% op die onderste blaaroppervlaktes. Spuitbehandelings met slegs fenhexamied, ongeag goeie blaarspuitbedekking, kon nie die B. cinerea infeksie ten volle voorkom nie, en infeksie van gemiddeld 34.6% en 40.8% is onderskeidelik op die boonste- en op die onderste blaaroppervlaktes waargeneem. Met die byvoeging van sekere byvoegmiddels het die voorkoms van B. cinerea betekenisvol verminder (2.9-17.1% en 10.0-30.8%, onderskeidelik), terwyl ander byvoegmiddels nie van die fenhexamied behandeling verskil het nie, hoewel hierdie middels meestal wel spuitdeponering verbeter het. Die effek van slegs Hydrosilicote en Solitaire, en in kombinasie met fenhexamied op ontkiemende Botrytis conidia, is bestudeer in ‟n histopatologiese studie deur middel van die gebruik van epifluoresensie mikroskopie op die blaaroppervlak. Duidelike verskille in die aantal dooie konidia, ontkiemingpersentasies en kiembuislengtes is tussen die byvoegmiddels en in kombinasie met fenhexamied waargeneem, waar sommige waarnemings moontlik aan die indirekte effek van die byvoegmiddel op B. cinerea toegeskryf kan word. Hierdie laboratoriumstudie wys duidelik dat byvoegmiddels oor goeie potensiaal beskik om die bio-effektiwiteit van die fungisied te verbeter deur die direkte verbetering van deponering op die wingerdblaaroppervlak. Dieselfde fluorometrie, fotomikrografie en digitale foto-analise protokol is in ‟n wingerd evaluasie om die kwantitatiewe en kwalitatiewe spuitdeponering van verskillende byvoegmidel dosisse and spuitvolumes te bepaal, gebruik. Die Furness visuele druppel meting tegniek is aanvanklik ingesluit om die optimale spuit volume met ‟n „STIHL SR400 motorised backpack mistblower‟ te bepaal deur visuele meetings van gedeponeerde pigment op Chardonnay blare onder ‟n swart ligbron. Beide protokolle wys dat kwantitatiewe spuitbedekking met ‟n toename in spuit volumes 40 L/ha tot 750 L/ha verbeter het, maar afgeneem het teen 900 L/ha, moontlik as gevolg van druppel-afloop. Die byvoeging van ‟n byvoegmiddel teen die aanbevole dosis en 600 L/ha wys uitstekende potensiaal om kwantitatiewe en kwalitatiewe deponering betekenisvol op boonste en onderste blaaroppervlaktes te verbeter. Agral 90, BB5, Nu-film-P, en Solitaire het deponering betekenisvol op boonste en onderste blare in vergelyking met die fenhexamied alleen en die water kontrole verbeter. Break-thru S 240 en Villa 51 het nie kwantitatiewe deponering verbeter nie, alhoewel verbeterde kwalitatiewe bedekking met hierdie produkte waargeneem is. ‟n Byvoegmiddel dosis effek (binne die registreerde dosis reeks) was duidelik waarneembaar, veral vir druppel retensie op die boonste oppervlak van blare. Agral 90 and Nu-film-P verbeter die spuit deponering betekenisvol met die hoër getoetste dosis, maar nie teen die lae dosis nie. Solitaire verbeter egter die deponering teen die laer dosis, maar minder deponering teen ‟n hoër dosis kan moontlik toegeskryf word aan oormatige druppel-afloop. In die geval van Villa 51 was geen betekenisvolle verbetering van spuitdeponering vir beide die behandelingsdosisse waargeneem nie. Spuitmengsels met byvoegmiddels, Agral 90 en Solitaire, het soortgelyke deponerings gelewer teen 600 L/ha in vergelyking met die fenhexamied kontrole teen 900 L/ha, maar deponering neem af teen hoër spuitvolumes met byvoegmiddels moontlik as gevolg van druppel-afloop. Hierdie studie wys duidelik die uitstekende potensiaal van Byvoegmiddels om kwantitatiewe en kwalitatiewe deponering te verbeter, maar beklemtoon die noodsaaklikheid van die korrekte gebruik van byvoegmiddel dosis en volume om die maksimum spuitdeponering op die teiken te verkry.

Thesis (MSc)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The latest strategies in the protection of crops against microbial pathogens are rooted in harnessing the natural, highly complex defense mechanisms of plants through genetic engineering to ultimately reduce the application of chemical pesticides. This approach relies on an in-depth understanding of plant-pathogen interactions to develop reasonable strategies for plant improvement. Among the highly specialized defense mechanisms in the plant’s arsenal against pathogen attack, is the de novo production of proteinaceous antimicrobial peptides (AMPs) as part of the plant’s innate immunity. These AMPs are small, cysteine-rich peptides such as plant defensins that are known for their broad-spectrum of antifungal activity. These plant defensin peptides have been found to be present in most, if not all plant species and the defensin encoding genes are over-represented in plant genomes. Most of these defensins are generally the products of single genes, allowing the plant to deliver these molecules relatively rapidly and with minimal energetic expense to the plant. These factors contribute to establishing AMPs as excellent candidates for genetic engineering strategies in the pursuit of alternative crop protection mechanisms. The first antimicrobial peptide identified and isolated from grapevine, Vv-AMP1, was found to be developmentally regulated and exclusively expressed in berries from the onset of ripening. Recombinantly produced Vv-AMP1 showed strong antifungal activity against a wide range of plant pathogenic fungi at remarkably low peptide concentrations in vitro, however, no in planta defense phenotype could thus far be linked to this peptide. In this study, the antifungal activity of Vv-AMP1 constitutively overexpressed in its native host (Vitis vinifera) was evaluated against grapevine-specific necrotrophic and biotrophic fungi. Firstly, a hardened-off genetically characterised transgenic V. vinifera (cv. Sultana) population overexpressing Vv-AMP1 was generated and morphologically characterized. In order to evaluate the in planta functionality of Vv-AMP1 overexpressed in grapevine, this confirmed transgenic population was subjected to antifungal assays with the necrotrophic fungus, B. cinerea and the biotrophic powdery mildew fungus, Erysiphe necator. For the purpose of infection assays with a biotrophic fungus, a method for the cultivation and infection with E. necator was optimized to generate a reproducible pathosystem for this fungus on grapevine. Detached leaf assays according to the optimized method with E. necator revealed programmed cell death (PCD) associated resistance linked to overexpression of Vv-AMP1 that can be compared to that of the highly resistant grapevine species, Muscadinia rotundifolia. Contrastingly, whole-plant infection assays with B. cinerea revealed that Vv-AMP1 overexpression does not confer V. vinifera with elevated resistance against this necrotrophic fungus. An in silico analysis of the transcription of defensin-like (DEFL) genes previously identified in grapevine was included in this study. This analysis revealed putative co-expression of these DEFL genes and other genes in the grapevine genome driven by either tissue- or cultivar specific regulation or the plant’s response to biotic and abiotic stress stimuli. In conclusion, this study contributed to our knowledge regarding Vv-AMP1 and revealed an in planta defense phenotype for this defensin in grapevine. In silico analysis of the DEFL genes in grapevine further revealed conditions driving expression of these genes allowing for inferences to be made regarding the possible biological functions of DEFL peptides in grapevine.
AFRIKAANSE OPSOMMING: Die nuutste strategieë wat deel vorm van die beskerming van plant gewasse teen mikrobiese patogene het hul oorsprong in die inspanning van die natuurlike, hoogs gekompliseerde verdedigingsmeganismes van die plant deur middel van genetiese enginieurswese ten einde die gebruik van chemiese plaagdoders te verlaag. Hierdie benadering maak staat op ‘n in-diepte begrip van plant-patogeen interaksies om verstandige strategieë vir plantverbetering te kan ontwikkel. Van hierdie hoogs-gespesialiseerde verdedigingsmeganismses in die plant se arsenaal teen patogeen aanvalle sluit die de novo produksie van proteinagtige antimikrobiese peptiede (AMPs) in as deel van die plant se ingebore immuunstelsel. Hierdie AMPs is klein, sisteïen-ryke peptiede soos die plant “defensins” en is bekend vir hul breë-spektrum antifungiese aktiwiteit. Hierdie plant defensinpeptiede word aangetref in meeste, indien nie alle plant spesies nie en die defensin koderende gene word oor-verteenwoordig in plant genome. Meeste van hierdie defensins is gewoonlik die produkte van enkele gene wat die plant in staat stel om hierdie molekules relatief spoedig en met minimale energie verbruik in die plant te vorm. Hierdie faktore dra by tot die vestiging van AMPs as uitstekende kandidate vir genetiese ingenieursstrategieë as deel van die strewe na alternatiewe gewasbeskermingsmeganismes. Die eerste antimikrobiese peptied wat geïdentifiseer en geïsoleer is uit wingerd, Vv-AMP1, word beheer deur die ontwikkelingsstadium en word eksklusief uitgedruk in korrels vanaf die aanvang van rypwording. Rekombinant-geproduseerde Vv-AMP1 het sterk antifungiese aktiwiteit getoon teen ‘n wye reeks plantpatogeniese swamme teen merkwaardige lae peptied konsentrasies in vitro, alhoewel geen in planta verdedigingsfenotipe tot dusver gekoppel kon word aan hierdie peptied nie. In hierdie studie was die antifungiese aktiwiteit van Vv-AMP1 wat ooruitgedruk is in sy natuurlike gasheerplant (Vitis vinifera) ge-evalueer teen wingerd-spesifieke nekrotrofiese- en biotrofiese swamme. Eerstens is ‘n afgeharde geneties-gekarakteriseerde transgeniese V. vinifera (cv. Sultana) populasie wat Vv-AMP1 ooruitdruk gegenereer en morfologies gekarakteriseer. Om die in planta funksionaliteit van Vv-AMP1 ooruitgedruk in wingerd te evalueer is hierdie bevestigde transgeniese populasie blootgestel aan antifungiese toetse met die nekrotrofiese swam, B. cinerea en die biotrofiese swam, Erysiphe necator. Vir die doel om infeksiestudies uit te voer met ‘n biotrofiese swam is ‘n metode geoptimiseer vir die kweek en infeksies met E. necator wat gelei het tot ‘n herhaalbare patosisteem vir hierdie swam op wingerd. Blaarstudies, volgens die pas-verbeterde metode vir E. necator infeksies het ‘n geprogrammeerde seldood-geassosieërde weerstand, gekoppel aan die ooruitdrukking van Vv-AMP1 onthul, wat vergelyk kan word met dié van die hoogs-weerstandige wingerdspesie, Muscadinia rotundifolia. Hierteenoor het heel-plant infeksie studies met B. cinerea onthul dat Vv-AMP1 ooruitdrukking geen verhoogde weerstand teen dié nekrotrofiese swam aan V. vinifera bied nie. ‘n In silico analise van die transkripsie van defensin-agtige (DEFL) gene wat vroeër in wingerd geïdentifiseer is, is by hierdie studie ingesluit. Hierdie analise het vermeende gesamentlike uitdrukking van hierdie DEFL gene en ander gene in die wingerd genoom onthul wat aangedryf word deur weefsel- of kultivar-spesifieke regulering of die plant se reaksie tot biotiese en abiotiese stress stimuli. Ten slotte, hierdie resultate het bygedra tot ons kennis in verband met Vv-AMP1 en het ‘n in planta verdedigingsfenotipe vir hierdie defensin in wingerd onthul. In silico analiese van die DEFL gene in wingerd het verder toestande onthul wat die uitdrukking van hierdie gene aandryf wat ons toelaat om aannames te maak ten opsigte van die moontlike biologiese funksies van DEFL peptiede in wingerd en ondersteun die opstel en toets van hipoteses vir die rol en megansimes van aksie van die wingerd defensin familie.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: The table grape industry employ a wide range of viticultural management practices in order to produce the high quality grapes demanded by the export market. A common contributor to degrading the quality of table grapes is the occurrence of berry split, which not only has an unattractive visual effect, but also increases the berries’ susceptibility to infection by spoilage organisms. A number of environmental conditions such as rainfall and humidity, and/or agricultural practices, such as irrigation, and high density canopies, can lead to higher plant cell water content. This in turn, can increase the potential of berry split to occur. To date, the main method of berry split prevention has been the management of plant water status by; (i) regulating irrigation withdrawal times, and (ii) covering of canopies if rainfall is predicted prior to harvest. The aim of this study was to determine the effect that irrigation frequency, as induced by irrigation withdrawals; as well as boron (B) and calcium (Ca) treatments, applied as bunch directed sprays, have on pre- and post-harvest berry split. To this end, a newly released late ripening, white seedless cultivar, SoutherngrapeOne was chosen as a model cultivar as it has a high susceptibility to berry split. SoutherngrapeOne vines were subsequently subjected to a range of irrigation frequencies based on typical irrigation scheduling used in the table grape industry, which comprised of a low, medium and high frequency. The low frequency was duplicated in order to demonstrate the effect that a heavy irrigation, just before harvest may have on berry split. These treatments were further subdivided to investigate the effect that B and Ca may have on berry split. For the B treatment, four Solubor1 bunch directed sprays were applied from 8mm berry size to véraison. The Ca treatment consisted of Stopit R 2 and Caltrac R 3 bunch directed sprays applied over the same period. In addition, a combination of the B and Ca treatment were applied to investigate any possible interaction. To account for the effect of water as solvent in the B and Ca treatments, and the spraying effect, pure water as treatment was also evaluated. Control vines received no sprays. The applied irrigation treatments resulted in different plant water status conditions. Separate applications of B and Ca treatments resulted in a decrease of B and Ca content in the flesh respectively. The control and combination treatment, of B and Ca resulted in the same of B and Ca content in the flesh. Furthermore, none of the applied treatments resulted in an increase of either B or Ca content in the berry skin. It was found that the medium frequency irrigation resulted in the best irrigation strategy to prevent pre-harvest berry split. Surprisingly, all the subtreatments: B, Ca, and combination of B and Ca, resulted in an increased incidence of pre-harvest berry split when compared to the control group for the 2006/07 season. However, in the 2007/08 season only the B treatment resulted in an increase of pre-harvest berry split. Concerning post-cold-storage physiological disorders, Ca treatments appear to have reduced berry drop, but increased decay. In the 2006/07 season, the B treatment resulted in reduced post-cold-storage berry split, whereas Btreatment in the 2007/08 season had no effect. Both B and Ca should be considered as having the potential to increase the appearance of hairline cracking. Calcium treatment also led to an increase in decay which may have been as a result of the splitting it contributed to. Low frequency irrigation recieving irrigation before harvest was found to result in browner stems. Low irrigation frequencies decreased the cell size of the berry skin. The Ca treatment gave rise to thicker (weaker) cell walls, this morphological change may be responsible for the physiological disorders it caused. From these findings, it can be deduced that poorly managed irrigation, together with unnecessary application of B and/or Ca may result in an increase of berry split and other physiological disorders, with subsequent financial losses for the producer.
AFRIKAANSE OPSOMMING; Die tafeldruifindustrie maak gebruik van ’n wye reeks wingerdkundige praktyke ten einde die hoë gehalte druiwe te produseer wat die uitvoermark vereis. Korrelbars is ’n algemene verskynsel wat afbreek maak tot die gehalte van tafeldruiwe. Behalwe dat voorkoms van die druiwe benaadeel word, verhoog dit ook in vatbaarheid vir infeksie deur verrottingsveroorsakende swamme. Hoë reënval en humiditeit, sowel as wingerdkundige praktyke soos besproeiing en hoë lowerdigtheid, wat kan lei tot verhoogde waterstatus in plante, kan lei tot ’n toename in korrelbars. Daar word hoofsaaklik van twee metodes gebruik gemaak om korrelbars te beheer, naamlik die bestuur van plantwaterstatus deur; (i) beheer van besproeiingsontrekkingstye en (ii) bedekking van lowers indien reën voorspel word voor oestyd. Die doel van hierdie studie was om vas te stel wat die invloed van besproeiings frekwensies sowel as trosgerigte boor (B) en kalsium (Ca), spuitbehandelings, op voor- en na-oes korrelbars het. Die onlangs vrygestelde laat rypwordende, wit, pitlose kultivar, SoutherngrapeOne is gebruik, aangesien dit hoogs gevoelig is vir korrelbars. Stokke is aan verskillende besproeiings intervalle, soos tipies gebruiklik in die tafeldruifindustrie, blootgestel. Hierdie intervalle bestaan uit n’ lae, medium en hoë besproeiings frekwensie. Die lae besproeiings frekwensie is herhaal ten einde die invloed van besproeiing net voor oestyd op korrelbars te ondersoek. Die invloed van B- en Ca-behandeling op korrelbars is ook ondersoek. Vir die B-behandeling is vier Solubor1 trosgerigte spuite aangewend vanaf 8mm korrelgrootte tot deurslaan. Vir die Ca-behandeling is Stopit R 2 en Caltrac R 3 as trosgerigte spuite oor dieselfde tyd toegedien. Kombinasiebehandelings is ook aangewend om enige interaksie tussen B en Ca te ondersoek. Waterbehandelings is ook toegedien om die invloed van water as oplosmiddel van B- en Ca-behandelings sowel as die spuit-effek te ondersoek. Kontrole stokke is ook ingesluit en het geen spuitebehandeling ontvang nie. Die besproeiingsbehandelings het verskillende plantwater toestande tot gevolg gehad, B- en Ca-behandelings het gelei tot ’n afname in B- en Cainhoud in die vleis onderskeidelik. Die kombinasie en kontrole behandelings het eenderse hoeveelhede B en Ca in die vleis tot gevolg gehad. Geen van die aangewende behandelings gelei tot ’n toename in B- en Ca-inhoud in die dop nie. Die resultate toon dat medium besproeiings frekwensie die beste besproeiingsstrategie is om voor-oes korrelbars te voorkom. In vergelyking met die kontrole-behandeling in 2006/07, het B, Ca en die kombinasie van B en Ca, ’n toename in voor-oes korrelbars tot gevolg gehad. In die 2007/08 seisoen het slegs die B-toediening egter tot ’n toename in voor-oes korrelbars gelei. Kalsium behandelings het ’n afname in los-korrels, maar ’n verhoging in korrelbars tot gevolg gehad. In 2006/07, het B-toediening tot ’n afname in korrelbars na koelopberging gelei, maar in die 2007/08 seisoen het dit geen effek gehad nie. Beide B- en Ca-toediening het die potensiaal om haarlyn barste te veroorsaak. Kalsium toediening het bederf verhoog wat moontlik aan die hoër bars wat dit induseer toegeskryf kan word. Lae besproeiings frekwensie, het bruiner stingels veroorsaak, en ook gelei tot ’n afname van selgrootte in die dop. Die Ca-toediening het aanleiding gegee tot dikker selwande in die dop. Hierdie anatomiese veranderinge kan moontlik die rede wees vir die verhoging in fisiologise afwykings. Van hierdie bevindinge kan ons aflei dat swak bestuur van besproeiing, sowel as die onnodige aanwending van B en/of Ca, kan aanleiding gee tot ’n toename in korrelbars en ander fisiologiese afwykings, en dus finansiële verliese vir die produsent inhou.

Thesis (MSc)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Plant-parasitic nematodes, consisting of a wide range of species, can cause severe economic losses in most agricultural food crops. Meloidogyne spp. (root-knot nematodes), Criconemoides xenoplax (ring nematode), Xiphinema index (dagger nematode) and Pratylenchus spp. (lesion nematodes) are some of the economically important plant-parasitic nematodes that pose a threat to viticulture and other perennial crops in South Africa. Worldwide there is ever-increasing pressure on pre-plant synthetic soil fumigants and post-plant nematicides. For sustainable nematode management, it is important to have a holistic approach; taking into consideration cultural, biological and chemical options as part of an integrated management approach. Biofumigation has the potential to fit into such an integrated management system and previous research indicates the positive response on soil-borne diseases, nematodes and weeds. Biofumigation occurs where certain plant species, containing glucosinolates (GSL) in the vacuole of the plant cells, come into contact (after cell maceration), with the enzyme myrosinase (MYR) situated in the cytoplasm of the cell, to form active compounds such as isothiocyanate (ITC). When this green manure is applied to infested soil, the ITC has the potential to have a direct suppressive effect on the soil-borne pathogens and there is also an indirect effect that can be expected after green manure soil amendment, because microbial activity is enhanced in the soil. Brassicas are known to possess GSL and MYR in their cells and thus have the potential to be utilized as biofumigation crops. There are, however, differences in the potential within the Brassicaceae family, based on different types and concentrations of GSL present in the different species. To ensure effective biofumigation it is important to use the correct brassica species and have a good understanding of the factors that have a positive impact on the biofumigation action. Laboratory bioassays were done to determine the potential of different cover crops to suppress Meloidogyne javanica and C. xenoplax, when applied as a green manure. The cover crops used for the bioassays included Oats (Avena sativa cv. Pallinup), White mustard (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) and Nemat (Eruca sativa cv. Nemat). The plant material was cut into small pieces and mixed with sterilised soil inoculated with either M. javanica or C. xenoplax. Results from the bioassays showed a significant suppression of M. javanica by the three biofumigation species: White mustard, Caliente 199 and Nemat. These results supported previous research, indicating the nematode suppressing effect due to the biofumigation action of certain brassica crops. Canola did not have the same suppressing impact on the M. javanica and gave comparable results to the control, indicating that Canola is not a good biofumigation crop for M. javanica suppression. In terms of biofumigation effect oats did not differ significantly from the control or the three brassicas: White mustard, Caliente 199 and Nemat. In the bioassays done for C. xenoplax no significant differences were found between the green manure treatments and the control. These results indicate that the different crops tested, including the three well known biofumigation crops, did not suppress the C. xenoplax at the applied biomass concentrations used in the bioassay. Crops can also be classified according to their host status for certain plant parasitic nematodes. Crop host trials were conducted to determine the crop host status of the five different cover crops, to M. javanica and C. xenoplax. The crops were planted in sterilised soil, inoculated with the latter plant-parasitic nematodes and left for 60 days, after which, a root gall index analysis was done for M. javanica and for 85 or 92 days after which C. xenoplax was extracted from the soil. All the crops evaluated had a significantly lower root gall index for M. javanica than the control. Nemat and Oats was classified as poor hosts for M. javanica. A visual inspection of the root systems of all the crops was performed to determine whether M. javanica managed to complete its lifecycle in the different root systems. On all root systems, M. javanica managed to form root galls and produce egg masses, from which (J2) juveniles emerged. This indicates that M. javanica did complete its lifecycle in the different root systems of the crops evaluated and that all the cover crops acted as hosts. The expression of the gall symptoms were, however, less severe on Nemat and Oats, compared to the others. In the C. xenoplax crop host trials, all except the Nemat treatment showed a significant difference, compared to the Tomato treatment, with lower C. xenoplax numbers being present in the other crops. The nematode numbers in the different crops, compared well with the control (only inoculated soil), indicating that the crops did not stimulate the reproduction of C. xenoplax. Canola had the lowest numbers of C. xenoplax present after the growing cycle and Caliente 199 also showed a declining trend. In South Africa, the use of annual cover crops in vineyards is an established soil cultivation practice. In a field study, Oats, White mustard, Canola, Caliente 199 and Nemat were established in a vineyard as cover crops for three growing seasons (2009/10, 2010/11, 2011/12), and evaluated for their biofumigation impact, as well as their host impact on the suppression of certain economically important plant-parasitic nematodes. Two cover crop management practices, namely mechanical incorporation (MC) into the top soil and chemical removal of the cover crop (CC) were applied to the different cover crops. Nematode samples were taken in the work row and in the vine row at different times to determine the nematode status. These periods were April/May, before planting the cover crops, as well as 0, 15, 30 and 60 days after the management practices were performed. The crop biomass, measured as dry matter production (DMP) in tons/ha, differed significantly between the different crops, but also showed substantial increases during the three cover crop growing seasons for most crops. During the three consecutive seasons, Canola (CC) and Caliente 199 (CC) showed a constant reduction in the C. xenoplax population in the vine row based on the 60 day analysis. This trend was also observed for the total plant-parasitic nematode population in the vine row for the three seasons, based on 60 day analysis. The same trend took place during the three-year trial period for all the different sampling periods (0, 15, 30 and 60 days). The results can be attributed to the host status of these crops and not primarily because of the biofumigation effect. Both the Canola (CC) and the Caliente (CC) had a substantial increase in DMP during the three growing seasons that might have played a role in this trend. White mustard (CC and MC) showed a significant increase in the C. xenoplax population in the vine row, over the three year period, based on the 60 day analysis. The same trend was found Nemat (CC) and weeds and nematicide (CC) measured at the same period. A positive result from the Meloidogyne sp. analysis was that there was no significant increase in the Meloidogyne sp. in the vine row during the three growing seasons based on the 60 day analysis. This trend was seen in all the different treatments. The results from this study opens the possibility to apply these cover crops as part of a crop rotation programme without expecting an increase in the Meloidogyne sp. population to occur in the vine row through time.
AFRIKAANSE OPSOMMING: Plantparasitiese nematodes, wat bestaan uit 'n wye verskeidenheid van spesies, kan lei tot ernstige ekonomiese verliese in die meeste landbou gewasse. Meloidogyne spp. (knopwortel nematode), Criconemoides xenoplax (ring nematode), Xiphinema index (dolk nematode) en Pratylenchus spp. (letsel nematode) is van dié belangrikste plantparasitiese nematodes wat 'n bedreiging inhou vir wingerd en ander meerjarige gewasse in Suid-Afrika. Wêreldwyd is daar tans toenemende druk op die uitfasering van voor-plant chemiese grondberoking middels en so ook op nauitplant nematisiede. Vir volhoubare nematode bestuur, is dit belangrik om 'n holistiese benadering te volg, in ag genome kulturele, biologiese en chemiese maatreëls as deel van 'n geïntegreerde benadering. Bioberoking het die potensiaal om deel uit te maak van so 'n geïntegreerde benadering en baie vorige navorsing bevestig hierdie positiewe reaksie, in terme van onderdrukking, wat bioberoking op grond-gedraagde siektes, nematodes en onkruid kan hê. Bioberoking kan beskryf word as die reaksie, wat plaasvind wanneer glukosinolaat (GSL), wat teenwoordig is in die vakuool van die plantselle, in kontak kom met die ensiem mirosinase (MYR), nadat selbreking plaasgevind het en die aktiewe verbinding isothiosianaat (ITC) en ander sekondêre metaboliete gevorm word. Wanneer hierdie groen plantmateriaal in die grond ingewerk word, kan ʼn direkte onderdrukkings effek, as gevolg van die ITC, asook ʼn indirekte onderdrukkings effek as gevolg van die stimulasie van mikrobe aktiwiteit, verwag word. Brassica gewasse is bekend daarvoor dat daar GSL en MYR in die plantselle teenwoordig is en hulle besit dus die potensiaal om ITC te vorm. Daar is egter verskille in hierdie potensiaal binne die Brassicaceae familie, wat gebaseer is op verskillende tipes en konsentrasies GSL. Die keuse van ʼn brassica spesie is dus belangrik, tesame met ʼn verskeidenheid van ander faktore, om optimale bioberoking te verseker. Laboratorium biotoetse is gedoen om die bioberokings effek van verskillende dekgewasse op Meloidogyne javanica en C. xenoplax, wanneer dit aangewend word as groenbemesting, te bevestig. Die dekgewasse wat gebruik is sluit in: Hawer (Avena sativa cv. Pallinup), Wit mosterd (Sinapis alba cv. Braco), Canola (Brassica napus cv. AV Jade), Caliente 199 (Brassica juncea cv. Caliente 199) en Nemat (Eruca sativa cv. Nemat). Die plantmateriaal is fyn opgesny en ingewerk in gesteriliseerde grond wat met onderskeidelik M. javanica en C. xenoplax geïnokuleer is. Resultate van die biotoetse vir M. javanica toon dat die drie gewasse; Wit mosterd, Caliente 199 en Nemat, wat alombekend is vir hul bioberoking potensiaal, ʼn betekenisvolle onderdrukkings op M. javanica tot gevolg gehad het. Hierdie biotoetse ondersteun vorige navorsing, waar effektiewe onderdrukking van sekere Meloidogyne spesies as gevolg van bioberoking verkry is. Die resultate dui ook aan dat Canola nie ʼn goeie opsie is vir effektiewe bioberoking om M. javanica onderdrukking te verkry nie. Die Hawer behandeling het nie betekenisvol van die kontrole of van die ander bioberokings gewasse verskil nie. Daar is geen betekenisvolle verskille verkry tussen die kontrole en die ander gewasse tydens die C. xenoplax biotoetse nie. Die resultate dui aan dat die dekgewasse, insluitende die drie bekende bioberokings gewasse, nie C. xenoplax onderdruk teen die toegediende biomassa konsentrasies nie. Gewasse kan ook geklassifiseer word op grond van hul gasheer status vir sekere nematode. Gasheer toetse is gedoen om die gasheer status van die verskillende dekgewasse vir M. javanica en C. xenoplax te bepaal. Dieselfde vyf verskillende dekgewasse is geplant in grond, wat vooraf onderskeidelik met M. javanica en C. xenoplax geïnokuleer is. Plante is gelos om vir `n spesifieke periode te groei waarna ʼn galindeks evaluasie is gedoen om die gasheer status vir M. javanica te bepaal en ʼn nematode ontleding gedoen is om die gasheer status vir C. xenoplax te bepaal. In die M. javanica gasheer toetse was die galindeks van al die gewasse betekenisvol laer as die kontrole. Nemat kan geklassifiseer word as ʼn swak gasheer vir M. javanica en het betekenisvol minder galle as al die ander gewasse, behalwe die Hawer, waarvan dit nie betekenisvol verskil het nie. Nemat pas dus goed in ʼn dekgewas program waar die doel is om die M. javanica populasie te onderdruk tydens die groei van die gewas. ʼn Visuele inspeksie van die wortelstelsels is ook gedoen ten einde te bepaal of die lewensiklus van M. javanica voltooi is. Wortelgalle en eiersakkies was teenwoordig in die wortels van al die verskillende gewasse en larwes het uit die eiers uitgebroei. Dit dui aan dat M. javanica daarin geslaag het om sy lewenssiklus op al die dekgewasse suksesvol te voltooi. Daar was aansienlik minder eiersakke by Nemat en Hawer; wat hul swak gasheer status bevestig. In die biotoetse vir die gasheerstatus van C. xenoplax het al die gewasse, behalwe Nemat, betekenisvol laer C. xenoplax getalle, in vergelyking met die Tamatie behandeling, tot gevolg gehad. Die nematode getalle was soortgelyk aan die kontrole (slegs geïnokuleerde grond), waar geen gewas in medium geplant is nie, en dui dus aan dat die getalle op die verskillende gewasse nie vermeerder het nie. Die Canola behandeling het die laagste C. xenoplax getalle gehad, gevolg deur Caliente 199. Hierdie gewasse toon dus die meeste potensiaal om aangewend te word in 'n rotasie stelsel of dekgewas program, waar die doel is om die C. xenoplax populasie te onderdruk. In Suid-Afrika is die aanwending van spesifieke eenjarige gewasse, as dekgewasse in wingerde, reeds ʼn standaard praktyk met verskeie voordele. In veldproewe oor ʼn tydperk van drie jaar (2009/10, 2010/11, 2011/12) is Hawer, Wit mosterd, Canola, Caliente 199 en Nemat aangeplant as dekgewasse in ʼn wingerd proefperseel. Die doel van die veldproewe was om die effek van dekgewasse op die plantparasitiese nematodes, wanneer dit aangewend word as bioberokings gewasse, te bepaal. Die gasheer status van die gewasse is ook ondersoek om te bepaal wat die effek sal wees op die nematode getalle. Twee dekgewas bestuurspraktyke is toegepas; meganiese inwerk van die dekgewasse in die bogrond (MC) en chemiese beheer van die dekgewasse (CC) en nematode monsters is op verskillende tye in die werksry en in die wingerdry geneem. Hierdie periodes sluit in April/Mei, voor die vestiging van die dekgewasse en 0, 15, 30 en 60 dae nadat die bestuurspraktyk toegepas is. Die dekgewas se biomassa produksie is, op grond van die droë massa produksie (DMP), in ton/ha gemeet, wat betekenisvol verskil het vir die verskillende dekgewas. Daar het ook `n duidelike toename in DMP plaasgevind oor die drie seisoene vir meeste gewasse. Gedurende die drie jaar periode het die Canola (CC) en Caliente 199 behandelings, gemeet 60 dae na die bestuurspraktyk, ʼn konstante afname getoon in die C. xenoplax in die wingerd ry. Dieselfde tendens het ook voorgekom gedurende hierdie periode in die totale plantparasitiese nematodes teenwoordig in die wingerd ry. Daar is ook ʼn geleidelike afnemende tendens in die C. xenoplax in die wingerd ry, oor die verskillende periodes 0, 15, 30 en 60 dae vir die drie opeenvolgende seisoene, waargeneem. Hierdie resultate kan primêr toegeskryf word aan die gasheer status van die dekgewasse, wat in die gasheer proewe as swak gashere vir C. xenoplax aangetoon is. Nog ʼn faktor wat hier ʼn rol speel is die feit dat beide die Canola (CC) en die Caliente 199 (CC) ʼn toename in DMP van meer as 2 ton, gedurende die drie jaar periode, gehad het; wat op sigself ook ʼn bydraende rol kon speel. Wit mosterd (CC en MC) het oor die drie seisoene ʼn betekenisvolle verhoging in die C. xenoplax populasie tot gevolg gehad, gebaseer op die 60 dae ontleding. Dieselfde tendens is ook opgemerk vir die ander behandelings, onder andere Nemat (CC) en die onkruid en aalwurmdoder (CC) behandeling. ʼn Baie positiewe resultaat na afloop van die drie seisoene is die feit dat daar nie ʼn betekenisvolle verhoging in die Meloidogyne sp. populasie in die wingerdry, op grond van die 60 dae onledings, plaasgevind het nie. Dit was ook die geval vir al die ander behandelings. Hierdie resultate ondersteun die moontlikheid om hierdie bioberokings gewasse deel te maak van ʼn geïntegreerde dekgewas benadering, sonder om in die proses die Meloidogyne sp. in die wingerd ry te verhoog.