Dissertations / Theses on the topic 'Grapes'

Thesis (M.S. in horticulture)--Washington State University, May 2010.
Title from PDF title page (viewed on July 7, 2010). "Department of Horticulture and Landscape Architecture." Includes bibliographical references (p. 113-119).

Copies of author's previously published articles inserted. Bibliography: leaves 143-167. Temperature may affect fruit-set in grapevines through its effect on the development of the flowers up to flower opening and on pollination, be it on the germination of the pollen and the growth of the pollen tube, or on the post-fertilisation growth of the ovule.

Good grapes are required to make good wine. Quality wines start in quality vineyards. Vineyard design, installation, and operation, including site location, trellis options, vine selection, and canopy management, along with when to harvest are discussed. While winemaking is the final phase in the pursuit of the winemaker's passion, it is but a simple formula. The beginning of a good wine is in a good vineyard. This study includes a financial projection for a 10-acre vineyard as well as for starting an onsite, complementary sized winery. Even though many small-to-medium vineyards-to-wineries have started over the last decade, the reason to enter into this type of business is not profit, but passion. Profits are relatively small for the time and labor investment, but the unique wine creations that result are amazing, for the winemaker and the one who enjoys the result.

At first glance, the Sonoran table grape industry may seem to fit the profile of a typical non-traditional agro-export system; and thus it might be expected that most of the generally accepted distinguishing characteristics of such systems would also be found here. However, a closer look at each link of this particular global commodity chain, and a greater appreciation of the historical precedents of the production region, reveals that individuals, rather than transnational corporations, are able to exert fairly high levels of control over the system, and reap a fair share of the benefits. Global commodity chain analysis, coupled with a political economy perspective, reveals that important changes further up the chain, at the retailing link, may in the future determine more of how table grapes are grown and distributed, and how the benefits of this production system are distributed. The analysis of changing agro-food systems is important because of their central role in determining the course of a nation and the well being of its people; in essence, as the food system goes, so goes the country. In diverse locations around the globe, food is increasingly being produced, distributed and marketed under the dictates of transnational corporations, which changes the role that nations, communities and individuals play in the global food system. Thus in recent years social scientists have been adding to the corpus of studies that constitute the political economy of the global agro-food system; this study intends to contribute to our knowledge of this important and rapidly evolving field.

Partial rootzone drying (PRD) is an irrigation management technique designed to reduce water use in grapevines without a decline in yield, thereby increasing water–use efficiency (measured as t/ML) (WUE). The principle of PRD is to keep part of the root system at a constant drying rate to produce soil-derived signals to above–ground plant organs to induce a physiological response. Major PRD effects include a reduced canopy size and greatly increased WUE with possible improvements in fruit quality. Although we have a good understanding of the hormonal physiology of PRD, little is known on the effect of PRD on partitioning of C, N and inorganic ions such as K. This thesis broadens our knowledge on the effects of PRD on grapevine field performance, growth and dry matter accumulation as well as its effects on physiology and biochemistry. In field experiments over 3 seasons, PRD reduced water use in grapevines without a significant decline in yield. PRD effects included reduced shoot growth and greatly increased WUE. Field–grown Cabernet Sauvignon, where the PRD grapevines were irrigated at half the control rate, and Shiraz where the PRD grapevines were irrigated at same rate as controls, confirmed that PRD is not simply an irrigation strategy that applies less water, rather it alters the way in which the plant responds to its environment, e.g. PRD alters the sensitivity of the stomatal response to atmospheric conditions and significantly influence enzymes that regulate nutrient accumulation and partitioning. PRD did not change the total amount of carbon and nitrogen on a whole plant basis. However, it caused a significant partitioning of carbon and nitrogen towards trunk, roots and fruit at the expense of shoot growth. This change in partitioning occurred as a result of altered activity of the enzymes controlling the assimilation of carbon and nitrogen. PRD significantly reduced nitrate reductase (NR) activity in grapevine leaves, which catalyses the first step in the assimilation of nitrate irrespective of the amount of water applied. The reduction in NR activity is correlated with the development of the PRD cycle and the associated reduction in stomatal conductance. PRD also significantly altered grapevine sucrolytic enzyme activity that regulate source:sink relationships. PRD showed transient increases in leaf sucrose phosphate synthase (SPS) activity (formation of sucrose) compared to control, but significantly reduced leaf neutral invertase (sucrose cleavage) and leaf starch content in both field and potted experiments. This may indicate an increased photosynthetic capacity and a reduction in its sink strength for sucrose in favor of organs such as fruit and roots. This hypothesis was reinforced by the fact that berries showed significantly higher levels in glucose and fructose early in the season. Berry sugar content and Brix at harvest however was unaffected. Although PRD had no significant effect on berry characteristics at harvest such as Brix and pH, it occasionally reduced per berry K+ content and increased total amino acid concentration that may lead to positive outcomes for wine quality. PRD–treated grapevine roots on the 'wet'– and 'drying'–sides differed greatly in enzyme activity and osmolality. PRD significantly increased osmolality in both wet and drying roots by increasing total osmolyte concentration that may facilitate the movement of water from wet to dry roots. The increases in osmolality were also associated with increased free polyamine production (spermidine and spermine) in PRD roots that may be related to increased root growth and density.
Thesis (Ph.D.)--School of Agriculture and Wine, 2005.

Thesis (MScAgric)--Stellenbosch University, 2003.
ENGLISH ABSTRACT: The table grape industry uses rapid cooling and packaging to protect grapes from desiccation and decay. Numerous packaging methods and combinations are used in the industry with each having their own advantages and disadvantages. Inferior postharvest grape quality can usually be ascribed to either deficient or excessive moisture in the carton. Berry split, decay and S02 damage are all disorders that are either caused or aggravated by wet berries in conjunction with elevated temperature. On the other hand, grapes that are exposed to desiccating conditions will develop brown stems and cause ineffective control by S02 gas generators. Moisture management is governed by perforated or non-perforated liners and/or by placing moisture absorbing materials inside the liners. To find the optimum liner perforation or moisture sheet combination, 'Thompson Seedless' and 'Red Globe' (Vitis vinifera Linnaeus) table grape quality was evaluated in various trials. The investigation of non-perforated liners compared to liners with different degrees of perforation concluded the following: Perforated liners benefit grape quality by decreasing S02 damage and berry split due to less moisture in the carton. These benefits, however, also lead to loss in quality due to increased stem desiccation and a lower S02 concentration in the packaging. The lower moisture content in the carton compensates for the lower S02 concentration, creating an environment less favourable for decay development. S02 damage and berry split decreased with an increase in degree of liner perforation, irrespective of the cultivars sensitivity to the disorder. Optimum level of perforation depends on the specific sensitivity of a cultivar to certain quality disorders and the characteristics of the quality disorders associated with a cultivar. Additionally, packing conditions such as product temperature and humidity should be considered. The specific costs associated with the advantages and disadvantages influenced by the degree of liner perforation will be the deciding factor in liner selection. The investigation of a clay-containing, moisture absorbing sheet emphasized the benefits and risks of absorbing large amounts of water within the packaging. Irrespective of using a perforated or non-perforated liner the influence of the desiccant sheet was evident throughout the trials. It benefited grape quality by lowering the incidence of berry split and S02 damage. However, decay control was impaired by the desiccant sheet, and stem desiccation was aggravated. The comparison of non-perforated liners with liners of various degrees of perforation showed the benefit of faster cooling rates of perforated liners. The various perforated liners showed little variation in airflow and cooling times. Morphological studies of various cultivars could not ascribe differences in stem condition to anatomical dissimilarities between various cultivars. It was found that 'Red Globe' had a much larger berry volume to stem weight ratio contributing to a high rate of water loss and stem dehydration. Stem visibility is high in 'Red Globe' due to the straggly, loose nature of the bunches. This heightens the perception of dry, brown stems and overemphasizes the actual severity of the disorder.
AFRIKAANSE OPSOMMING: Die tafeldruifbedryf gebruik versnelde verkoeling en verpakking om druiwe te beskerm teen uitdroging en bederf. Verskeie verpakkingsmetodes word gebruik in die industrie waarvan elkeen sy eie voor- en nadele het. Ondergeskikte na-oes kwaliteit kan gewoonlik toegeskryf word aan óf te min óf te veel vog in die karton. Korrelbars, S02 skade en bederf is almal kwaliteitsdefekte wat óf veroorsaak word, óf vererger word deur nat korrels, saam met 'n verhoging in temperatuur. In teenstelling hiermee sal druiwe wat blootgestel word aan droë toestande, bruin stingels ontwikkel en S02 beheer salook ondoeltreffend wees. Vog in verpakking word beheer deur geperforeerde of nie-geperforeerde binnesakke en/of deur vogabsorberende materiaal binne die binnesak te plaas. Om die optimum binnesak perforasie of vogabsorberende vel kombinasie te vind is 'Thompson Seedless' en 'Red Globe' (Vitis vinifera Linnaeus) tafeldruif kwaliteit ge-evalueer in verskeie proewe. Die bestudering van nie-geperforeerde binnesakke teenoor binnesakke met verskillende grade van perforasies het die volgende resultate gelewer: Geperforeerde binnesakke bevoordeel druif kwaliteit deur die vermindering van S02 skade en korrelbars weens minder vog in die karton. Hierdie voordele sal egter lei tot verlies in kwaliteit weens die vinniger uitdroging van stingels en die verlaging van S02 konsentrasie in die verpakking. Die laer vog inhoud in die karton vergoed vir die vermindering van S02 konsentrasie, omdat minder gunstige toestande vir die ontwikkeling van bederf geskep word. S02 skade en korrelbars het verminder met 'n vermeerdering van perforasies, ongeag die kultivar se sensitiwiteit vir die defekte. Optimum vlakke van perforasie is afhanklik van die spesifieke sensititiwiteit van 'n kultivar tot sekere kwaliteitsdefekte, en eienskappe van die kwaliteitsdefekte wat geassosieer word met die kultivar. Boonop moet verpakkingsomstandighede soos produktemperatuur en humiditeit ook in gedagte gehou word. Die spesifieke koste verbonde aan die voor- en nadele wat beïnvloed word deur die graad van perforasie sal die bepalende faktor wees wanneer 'n binnesak gekies word. Die bestudering van 'n klei-bevattende, vogabsorberende vel het bewys dat dit voordele en risiko's inhou om groot hoeveelhede vog te absorbeer. Ongeag die gebruik van 'n geperforeerde of nie-geperforeerde binnesak, was die invloed van die desikkante vel duidelik in al die proewe. Dit was voordelig vir druif kwaliteit deurdat dit korrelbars en S02 skade verminder het. Bederfbeheer is egter verswak deur die desikkante vel, en stingel uitdroging IS vererger. Die vergelyking van nie-geperforeerde binnesakke met verskillende grade van geperforeerde binnesakke het die voordeel bewys van vinniger verkoelinstempo's van die geperforeerde binnesak. Verskille in die graad van perforasie het 'n klein invloed gehad op die lugvloei en verkoelingstempo 's. Bestudering van verskeie kultivars kon geen morfologiese verskille uitwys wat variasie in stingelkwaliteit tussen kultivars kan verklaar nie. Dit is bevind dat 'Red Globe' 'n baie groter korrelvolume tot stingelgewig verhouding het. Stingels is meer sigbaar by 'Red Globe' weens die yl, los aard van die trosse. Dit verhoog die persepsie van droë, bruin stingels en dit oorbeklemtoon die voorkoms van die defek.

Thesis (PhD(Agric))--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Postharvest quality of fresh table grapes is usually preserved through cooling using cold air. However, cooling efficiencies are affected by the multi-scale packaging that is commercially used for handling grapes after harvest. There is usually spatial temperature variability of grapes that often results in undesirable quality variations during postharvest handling and marketing. This heterogeneity of grape berry temperature inside multi-packages is largely due to uneven cold airflow patterns that are caused by airflow resistance through multi-package components. The aims of this study were therefore to conduct an in-depth experimental investigation of the contribution of grape multi-packaging components to total airflow resistance, cooling rates and patterns of grapes inside the different commercially used multi-packages, and to assess the effects of these multi-packages on table grape postharvest quality attributes. A comprehensive study of moisture loss from grapes during postharvest storage and handling, as well as a preliminary investigation of the applicability of computational fluid dynamics (CFD) modeling in predicting the transport phenomena of heat and mass transfer of grapes during cooling and cold storage in multi-packages were included in this study. Total pressure drop through different table grapes packages were measured and the percentage contribution of each package component and the fruit bulk were determined. The liner films contributed significantly to total pressure drop for all the package combinations studied, ranging from 40.33±1.15% for micro-perforated liner film to 83.34±2.13 % for non-perforated liner film. The total pressure drop through the grape bulk (1.40±0.01 % to 9.41±1.23 %) was the least compared to the different packaging combinations with different levels of liner perforation. The cooling rates of grapes in the 4.5 kg multi-packaging were significantly (P<0.05) slower than that of grapes in 5 kg punnet multi-packaging, where the 4.5 kg box resulted in a seven-eighths cooling time of 30.30-46.14% and 12.69-25.00% more than that of open-top and clamshell punnet multi-packages, respectively. After 35 days in cold storage at -0.5°C, grape bunches in the 5 kg punnet box combination (open-top and clamshell) had weight loss of 2.01 – 3.12%, while the bunches in the 4.5 kg box combination had only 1.08% weight loss. During the investigation of the effect of different carton liners on the cooling rate and quality attributes of ‘Regal seedless’ table grapes in cold storage, the non-perforated liner films maintained relative humidity (RH) close to 100 %. This high humidity inside non-perforated liner films resulted in delayed loss of stem quality but significantly (P ≤ 0.05) increased the incidence of SO2 injury and berry drop during storage compared to perforated liners. The perforated liners improved fruit cooling rates but significantly (P ≤ 0.05) reduced RH. The low RH in perforated liners also resulted in an increase in stem dehydration and browning compared to non-perforated liners. The moisture loss rate from grapes packed in non-perforated liner films was significantly (P<0.05) lower compared to the moisture loss rate from grapes packed in perforated liner films (120 x 2 mm and 36 x 4 mm). The effective moisture diffusivity values for stem parts packed in non-perforated liner films were lower than the values obtained for stem parts stored without packaging liners, and varied from 5.06x10-14 to 1.05x10-13 m2s-1. The dehydration rate of stem parts was inversely proportional to the size (diameter) of the stem parts. Dehydration rate of stems exposed (without liners) to circulating cold air was significantly (P<0.05) higher than the dehydration rates of stems packed in non-perforated liner film. Empirical models were successfully applied to describe the dehydration kinetics of the different parts of the stem. The potential of cold storage humidification in reducing grape stem dehydration was investigated. Humidification delayed and reduced the rate of stem dehydration and browning; however, it increased SO2 injury incidence on table grape bunches and caused wetting of the packages. The flow phenomenon during cooling and handling of packed table grapes was also studied using a computational fluid dynamic (CFD) model and validated using experimental results. There was good agreement between measured and predicted results. The result demonstrated clearly the applicability of CFD models to determine optimum table grape packaging and cooling procedures.
AFRIKAANSE OPSOMMING: Naoes kwaliteit van vars tafeldruiwe word gewoonlik behou deur middel van verkoeling van die produk met koue lug. Ongelukkig word die effektiwiteit van dié verkoeling beïnvloed deur die multivlakverpakking wat kommersieel gebruik word vir die naoes hantering van druiwe. Daar is gewoonlik ruimtelike variasie in die temperatuur van die druiwe wat ongewenste variasie in die kwaliteit van die druiwe veroorsaak tydens naoes hantering en bemarking. Die heterogene druiwetemperature binne die multivlakverpakkings word grootliks veroorsaak deur onegalige lugvloeipatrone van die koue lug as gevolg van die weerstand wat die verskillende komponente van die multivlakverpakkings teen lugvloei bied. Die doel van hierdie studie was dus om ‘n indiepte eksperimentele ondersoek te doen om die bydrae van multivlakverpakking op totale lugvloeiweerstand, verkoelingstempo’s en –patrone van druiwe binne kommersieël gebruikte multivlakverpakkings te ondersoek, asook die effek van die multivalkverpakking op die naoes kwaliteit van druiwe te bepaal. ‘n Omvattende studie van vogverlies van druiwe tydens naoes opberging en hantering, asook ‘n voorlopige ondersoek na die bruikbaarheid van ‘n berekende vloei dinamika (BVD) model om die bewegingsfenomeen van hitte en massa oordrag van druiwe tydens verkoeling en koelopberging in multivlakverpakkings te voorspel, was ook by die studie ingesluit. Die totale drukverskil deur verskillende tafeldruif verpakkingssisteme is gemeet en die persentasie wat deur elke verpakkingskomponent en die vruglading bygedra is, is bereken. Van al die verpakkingskombinasies wat gemeet is, het die voeringfilms betekenisvol tot die totale drukverskil bygedra, en het gewissel van 40.33±1.15% vir die mikro geperforeerde voeringfilm tot 83.34±2.13 % vir die nie-geperforeerde voeringfilm. Die totale drukverskil oor die druiflading (1.40±0.01 % to 9.41±1.23 %) was die minste in vergelyking met die verskillende verpakkingskombinasies met die verskillende vlakke van voeringperforasies. Die verkoelingstempos van die druiwe in die 4.5 kg multiverpakking was betekenisvol (P<0.05) stadiger as vir die druiwe in die 5 kg handmandjie (‘punnet’) multiverpakking. Die 4.5 kg karton het ‘n seweagstes verkoelingstyd van 30.30-46.14% en 12.69-25.00% langer, respektiewelik, as oop-vertoon en toeslaan-‘punnet’ multiverpakkings gehad. Na 35 dae van koelopberging by -0.5°C het druiwetrosse in die 5 kg ‘punnet’-kartonkombinasies (oop-vertoon en toeslaan-’punnet’) ‘n massaverlies van 2.01 – 3.12% gehad, terwyl die trosse in die 4.5 kg kartonkombinasie slegs ‘n 1.08% massaverlies gehad het. In die ondersoek na die effek van verskillende kartonvoerings op die verkoelingstempo en kwaliteitseienskappe van ‘Regal seedless’ tafeldruiwe tydens koelopbering, het die nie-geperforeerde kartonvoerings ‘n relatiewe humiditeit (RH) van byna 100 % gehandhaaf. Hierdie hoë humiditeit in die nie-geperforeerde voeringfilms het ‘n verlies in stingelkwaliteit vertraag, maar het die voorkoms van SO2-skade en loskorrels betekenisvol (P < 0.05) verhoog in vergelyking met geperforeerde voerings. Die geperforeerde voerings het vrugverkoelingstempos verbeter, maar het die RH betekenisvol (P ≤ 0.05) verlaag. Die lae RH in die geperforeerde voerings het gelei tot ‘n verhoging in stingeluitdroging en –verbruining in vergelyking met die nie-geperforeerde voerings. Die vogverliestempo uit druiwe verpak in nie-geperforeerde voeringfilms was betekenisvol (P<0.05) stadiger in vergelyking met druiwe verpak in geperforeerde voeringfilms (120 x 2 mm and 36 x 4 mm). Die effektiewe vogdiffusiewaardes vir stingelgedeeltes verpak in nie-geperforeerde voeringfilms was stadiger as vir stingelgedeeltes wat verpak is sonder verpakkingsvoerings, en het gevarieer van 5.06x10-14 – 1.05x10-13 m2s-1. Die uitdrogingstempo van stingelgedeeltes was omgekeerd eweredig aan die grootte (deursnit) van die stingelgedeeltes. Die uitdrogingstempo van stingels wat blootgestel was (sonder voerings) aan sirkulerende koue lug was betekenisvol (P<0.05) hoër as die uitdrogingstempos van stingels wat verpak was in nie-geperforeerde voeringfilms. Empiriese modelle is gebruik om die uitdrogingskinetika van die verskillende stingelgedeeltes te beskryf. Die potensiaal van koelkamer humidifisering in die vermindering van die uitdroging van druifstingels is ondersoek. Humidifisering het stingeluitdroging vertraag en het die tempo van stingeluitdroging en -verbruining verminder, maar dit het die voorkoms van SO2-skade op die tafeldruiftrosse verhoog en het die verpakkings laat nat word. Die bewegingsfenomeen tydens verkoeling en hantering van verpakte tafeldruiwe is ook ondersoek deur gebruik te maak van ‘n BVD model en is bevestig met eksperimentele resultate. Daar was goeie ooreenstemming tussen gemete en voorspelde resultate. Die resultaat demonstreer duidelik die toepaslikheid van BVD-modelle om die optimum tafeldruifverpakkings- en verkoelingsprosedures te bepaal.
PPECB and Postharvest Innovation Programme (PHI-2) for their financial support

Thesis (MScAgric)--Stellenbosch University, 2008.
ENGLISH ABSTRACT: Fruit quality is the most important factor that determines prices for the fruit in the international markets. Although different consumers perceive quality differently there are quality variables that are always associated with poor quality by all consumers. In table grapes (Vitis vinifera L.) these variables may include overall appearance, stem condition, SO2 damage, decay, berry browning and shatter. The presence of these quality defects negatively affects prices and most often results in quality claims. Cooling is the most widely used method to reduce the postharvest loss of fruit quality. In South Africa, most deciduous fruits including table grapes are forced air cooled to a statutory pulp temperature of –0.5°C prior to shipping in an effort to preserve quality, thus ensuring good market prices for the fruits. Despite these efforts, there are still quality claims from the markets and this reduces the returns to the growers. The objectives of this research were to: (i) see if cooling time can be reduced by cooling to higher pulp temperatures of 1.5°C and 3°C without causing quality losses, thus improving the throughput of the cold rooms; (ii) see if the problem of berry browning can be alleviated by cooling grapes to higher pulp temperature, and (iii) see whether pallet positioning in the cooling tunnels and reefer container affect quality. The trends showed better quality when ‘Victoria’ and ‘Regal Seedless’ were forced air cooled (FAC) to pulp temperatures of 1.5 °C and 3 °C as opposed to –0.5 °C. There were no economic losses associated with pre-cooling grapes to pulp temperatures of 1.5 °C and 3 °C. There were no significant differences in berry browning related to pre-cooling treatments. However, cooling time was reduced significantly. In most of the cooling tunnels and reefer containers used in this trial, grape quality results showed no significant differences between the positions in the stack and in reefer containers. However, in cases where there were significant differences, the middle and the rear positions showed better grape quality in terms of stem condition (dry and brown stems) than the front position (near fan) in both the pre-cooling stack and reefer containers. The trends showed that the front is cooler than the back of the pre-cooling stack. The pulp temperature differences between the front and rear positions in the reefer container were as high as 1.23 °C. The trends also showed that the bottom layers of the pallets were cooler than the top layers in the reefer container. FAC to 3°C resulted in a constant reduction in percentage electrolyte leakage after 4 weeks of storage at –0.5°C, while FAC to 1.5°C, -0.5°C and static room cooling (control) in some cases showed an initially low electrolyte leakage followed by an increase in leakage after 4 weeks of storage. FAC grapes to higher pulp temperatures of 3°C and 1.5°C could reduce the cooling time, thereby improving the throughput of cold rooms. There was no clear evidence to suggest that browning was due to pre-cooling practices. Both preharvest and postharvest conditions need to be further investigated to better understand the problems of browning in white table grapes.
AFRIKAANSE OPSOMMING: Vrugkwaliteit is ʼn kritiese faktor in die bepaling van pryse op die internasionale markte. Alhoewel daar variasie voorkom tussen verbruikers in wat vrugkwaliteit is, bly sekere aspekte altyd onveranderd. Ononderhandelbare kwaliteit aspekte in tafeldruiwe (Vitis vinifera L.) sluit die algemene voorkoms, toestand van die trosstingels, SO2 skade, bederf, korrel verbruining en los-korrels in. Indien enige van die kwaliteit-defekte voorkom het dit ʼn negatiewe impak op die prys en lei gewoonlik tot gehalte eise. Verkoeling word algemeen gebruik om die verlies van na-oes kwaliteit te verminder. Die meeste sagtevrugte geproduseer in Suid Afrika (insluitend tafeldruiwe) ondergaan geforseerde verkoeling tot ʼn statutêre pulptemperatuur van -0.5°C, voor verskeping. Ondanks hierdie maatreëls om hoë pryse te verseker, is daar steeds kwaliteiteise in die mark wat lei tot ‘n laer inkomste vir produsente. Die navorsing het dus ten doel gehad om : (i) te bepaal of die tyd van verkoeling verminder kan word, indien na hoër pulptemperature van 1.5°C en 3°C verkoel kan word, sonder ‘n verlies in kwaliteit en sodoende die deurvloeitempo van die koelkamers verhoog; (ii) om te bepaal of die voorkoms van korrelverbruining verlaag kan word indien tot hoër pulp-temperature verkoel word, en (iii) laastens om te bepaal of posisie van die palet in die verkoelingstonnel en verskepingshouer ʼn invloed het op vrugkwaliteit. Tendense toon dat ‘Victoria’ en ‘Regal Seedless’ kwaliteit beter was indien verkoel tot pulptemperature van 1.5°C en 3°C in vergelyking met -0.5°C. Daar was geen ekonomiese verliese waargeneem indien die hoër verkoelingstemperature gebruik is nie. Alhoewel daar geen betekenisvolle verskille in korrelverbruining voorgekom het tussen temperatuur behandelings nie is die verkoelingsperiode verkort. In die meeste van die verskepingshouers, asook in posisies tydens geforseerde verkoeling is daar geen betekenisvolle verskille waargeneem nie. In die gevalle waar daar egter wel betekenisvolle verskille voorgekom het, het die middel en agter posisies beter vrugkwaliteit gehad as die voorste posisie tydens verkoeling asook houerverskeping. Die palette aan die voorkant (naby die waaier) het as ʼn algemene tendens laer temperature as in die agterkant van die verkoelingstonnel. Verskille in pulptemperature tussen palette in die voor en agterkant van verskepingshouers was so hoog as 1.23°C. Die temperatuurdata het uitgewys dat die onderste laag kartonne neig om by ‘n laer temperatuur te wees as die boonste lae kartonne tydens houerverskeping. Geforseerde verkoeling teen 3°C het gelei tot ‘n afname in persentasie elektrolietlekkasie na 4 weke van verkoeling teen -0.5°C. Terselfdertyd het geforseerde verkoeling tot 1.5°C en -0.5°C asook statiese verkoeling (kontrole) in sekere gevalle gelei tot ‘n laer aanvanklike uitlek van elektrolietlekkasie, gevolg deur ʼn verhoging na 4 weke opberging. Geforseerde verkoeling van tafeldruiwe tot pulptemperature van 1.5°C en 3°C verkort die verkoelingstyd en verhoog dus die deurvloeitempo in die verkoelingskamers. Daar was gedurende die studie geen duidelike bewyse gevind dat korrelverbruining voorkom as gevolg van verkoelingspraktyke nie. Beide voor en na-oes praktyke sal verder ondersoek moet word om die invloed daarvan te bepaal op die verbruining van wit tafeldruiwe.

The potential of dielectric heating with microwaves at 2450 MHz for drying grapes into raisins was studied. Feasibility studies in a conventional microwave oven were successful. A new microwave drying system equipped with specialized instrumentation and data acquisition components and permitting full control of microwave power levels and duration of application was then developed and used for detailed experimental work.
It was found that when the grapes were dipped in surfactants, as is common practice in the raisin industry, microwave drying was not only faster than convective drying but also had a much lower specific energy requirement. However, it was also possible to obtain raisins of adequate quality without dippings. Good quality light coloured raisins were obtained without sulphur dioxide fumigation. Thus, microwave drying has potential in reducing both the quantity of chemicals entering at this point in the food chain and the energy consumed for food preservation.
The shrinkage and density of grapes were found to be linearly related to moisture content; initial size and method of drying had no influence. (Abstract shortened by UMI.)

Smoke derived taint in grapes and wine is an issue of increasing significance and severity for the wine industry internationally. On commencement of this research, insufficient knowledge existed as to the effects of smoke on grapevines and the development of smoke taint in wine, with no substantial published information. This research was undertaken to investigate the effect of smoke exposure to grapevines on the development of smoke aromas, flavours and compounds in final wines. As such, this study pioneers the purposeful application of smoke to grape bunches and field-grown grapevines to establish the direct link between smoke exposure and the development of smoke taint in wine.This research identified key periods of grapevine sensitivity to smoke uptake as: (1) from shoots 10 cm in length to full-bloom (low levels of smoke taint); (2) from berries pea size to the onset of veraison (variable levels of smoke taint); and (3) from 7 days post veraison to harvest (high levels of smoke taint). A novel smoke application methodology consisting of a smoke generator and greenhouse-grade tent was developed to facilitate the accurate application of smoke treatments to field-grown grapevines. Smoke treatments were applied to grapevines at key stages during the seasonal growth cycle, on repeated occasions and at a range of densities and durations.Elevated concentrations of guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-ethylphenol, eugenol and furfural were detected, by gas chromatography-mass spectrometry analysis, in wines made from fruit exposed to smoke; whereas these compounds were either not detected or detected in trace concentrations in wines produced from unsmoked (control) fruit. Wine sensory analysis established a difference between smoked and unsmoked wines, with smoked wines exhibiting ‘smoky’, ‘dirty’, ‘earthy’, ‘burnt’ and ‘smoked meat’ aromas. The density and duration of smoke exposure to grapevines was found to affect the chemical composition and sensory properties of wine and repeated smoke applications demonstrated a cumulative effect.

Bibliography: p. 261-273. The general hypothesis tested in this study was that: 'partial drying of the root system of grapevines will result in reduced vegetative growth with beneficial effects for fruit yield, fruit composition and water-use efficiency'. Previously published work has suggested that partial drying of the root system may give rise to non-dydraulic root-derived signals capable of changing leaf development and transpiration.

Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Grapevine is worldwide an agronomically important crop. Traditionally selective breeding has been used to improve existing cultivars. In the last ten years, however, the advent of biotechnology has shortened these breeding programmes by producing transgenic grapevine. Because this new technology is aimed at the possible genetic manipulation of the ripening process in grape berries, it is important to elucidate all the mechanisms that may be involved in ripening. The aim of the present study was the identification of genes that play an important role during the ripening process in grape berries. This was achieved by investigation of putative differentially expressed genes in ripening Chardonnay berries isolated through subtractive hybridisation. Two subtraction libraries, representing early and late ripening stages were constructed. Four of the ten genes analysed exhibited expression during berry ripening. One of the four genes was expressed in a tissue and stage specific manner. Further characterisation of eight of the DNA and protein sequences revealed that the putative translation products of these clones had homologues that are involved in amongst others cell wall structure in other species. These included UDP-glucose dehydrogenase, which is involved in the synthesis of hemicellulose precursors. The remaining seven clones encoded putative stress response proteins. These included two heat shock proteins, a vacuolar pyrophosphatase and a protein involved in cell division. It is suggested that specific grape mRNAs accumulate in response to stresses such as the storage of high concentrations of sugars and rapid cell expansion. These processes occur rapidly during the ripening of berries. Accumulation of specific mRNAs can be attributed to part of the normal ripening developmental programme.
AFRIKAANSE OPSOMMING: Druiwe is wêreldwyd 'n belangrike landbougewas en kultivars word tradisioneel deur middel van tydsame selektiewe teling verbeter. Die tyd wat hieraan bestee word, kan verkort word deur die implementering van biotegnologie en die produksie van transgeniese duiwe. Omdat hierdie nuwe tegnologie op die moontlike genetiese manipulering van die rypwordingsproses in druiwe gemik is, is dit belangrik dat alle meganismes betrokke by rypwording ondersoek en verstaan word. Die doel van hierdie studie was om gene wat moontlik tydens die rypwordingsproses in druiwe 'n rol kan speel, te identifiseer. Hierdie doel is bereik deurdat differensieel uitgedrukte gene uit die kultivar Chardonnay geïsoleer is met behulp van verrykingsbiblioteke vanuit jong en volwasse druiwekorrels. Vier van die tien gene wat geanaliseer is, word uitgedruk tydens die rypwordingsproses. Verder het een van die vier gene weefsel- en rypwordingstadium- spesifisiteit getoon. Volledige karakterisering van agt van die DNA- en proteïenvolgordes het aangedui dat die proteïenprodukte van hierdie gene homoloog is aan volgordes wat onder andere by selwandstruktuur betrokke is. Dit sluit UDP-glukose dehidrogenase in, wat betrokke is by die sintese van hemi-sellulose boustene. Die ander sewe gene kodeer vir moontlike spanningsproteïene. Twee hitteskokproteïene, 'n vakuolêre pirofosfatase en 'n proteïen wat betrokke is by selverdeling is geïdentifiseer. Daar word voorgestel dat druiwe mRNA versamel in reaksie op spanningsituasies soos die berging van hoë konsentrasies suikers en selvergroting. Hierdie prosesse vind baie vinnig plaas tydens rypwording. Versameling van spesifieke mRNAs kan toegeskryf word as 'n normale deel van die rypwordingsproses.

Growth, productivity and fruit quality of grapevines are closely linked to soil water availability. Withholding of water for any length of time results in slowed growth. If drought continues yield may be lost. Vines can be manipulated to stimulate early defence mechanisms by decreasing soil water availability. By using an irrigation technique, which allows for separate zones with different soil moisture status, it is possible to stimulate response mechanisms of the root system which are normally related to water stress. The difficulty of separating 'wet' and 'dry' zones was initially overcome by using split-root plants with root systems divided between two containers. Such experiments on split-root model plants resulted in the development of an irrigation technique termed partial rootzone drying (PRD). Results from irrigation experiments using PRD have shown that changes in stomatal conductance and shoot growth are some of the major components affected (Dry et al., 1996). The idea of using irrigation as a tool to manipulate stress responses in this way had its origin in the concept that root- derived abscisic acid (ABA) was important in determining stomatal conductance (Loveys, 1984). Later experiments on split-root plants have demonstrated that many effects of water stress can be explained in terms of transport of chemical signals from roots to shoots without changes in plant water status (Gowing et al., 1990). The necessary chemical signals are provided by the dry roots, and the wet roots prevent the development of deleterious water deficits. The general hypothesis tested during this study was that partial drying of the root system gives rise to a change in the supply of root-derived chemical signals which determine changes in grapevine physiology, thereby affecting fruit quality. Experiments were conducted on split-root vines (Vitis vinifera L. cvs. Cabernet Sauvignon and Chardonnay) grown in pots of different sizes, on field-grown vines which had either their root system divided by a plastic membrane (Vitis vinifera L. cv. Cabernet Sauvignon on own roots or grafted on Ramsey rootstocks) or conventional vines with a non-divided root system (Vitis vinifera L. cv. Cabernet Sauvignon, Shiraz and Riesling) with a commercial PRD irrigation design. The irrigation treatments were vines receiving water on both sides (control) and PRD-treated vines, which only received water on one side at any time. The frequency of alternation of 'wet' and 'dry' sides was determined according to soil moisture and other influences such as rainfall and temperature. In most of the experiments the irrigation was alternated from one side to the other every 10 to 15 days. Chemical signals from roots: the role of ABA and cytokinins Studies on chemical signals have concentrated on ABA and cytokinins (CK). An improved stable isotope dilution protocol, which enables analysis of ABA and CK from the same tissue sample, was developed. Analysis of cytokinins focused on zeatin (Z), zeatin riboside (ZR), zeatin glucoside (ZG) and iso pentenyl adenine (iP). Roots are relatively inaccessible, particularly in field situations. To enable easier access to roots of field-grown vines, split-root vines were planted in a trench which was refilled with a sandy soil. This created a homogenous soil substrate and did not restrict root growth while still allowing access to roots under field conditions. Analyses of root samples of field-grown vines have shown that cytokinins and ABA may originate in roots and their concentrations can be substantially altered during an irrigation cycle. Alternating soil water conditions showed that [ABA] in roots on the 'dry' side was significantly higher compared with the 'wet' side. Due to a reduction in CK on the 'dry' side of PRD-treated vines, the ratio between ABA and CK was substantially changed during an irrigation cycle. The ABA levels in root tissue and in petiole xylem sap were negatively related to stomatal conductance. This further suggests that ABA, mostly synthesized on the 'dry' side of the root system, might be responsible for a decline in stomatal conductance. Furthermore, a higher pH of petiole xylem sap was observed in PRD-treated vines which may also contribute to the regulation of stomatal conductance. Studies on stomatal patchiness showed that non-uniform stomatal aperture occurred in field-grown vines under natural environmental conditions and was more abundant under PRD conditions. The degree of stomatal opening, determined by using a water infiltration technique, correlated with measurement of stomatal conductance. Exogenous application of a synthetic cytokinin (benzyl adenine) can override the possible ABA-mediated stomatal closure resulting from PRD treatment, providing further evidence for the in vivo role of these growth regulators in the control of stomatal conductance. The effect of benzyl adenine was transient, however, requiring repeated applications to sustain the reversal. In addition, CKs may also be important in influencing grapevine growth. Following several weeks of repeated spray applications with benzyl adenine, it was found that the development of lateral shoots in PRD-treated vines was enhanced compared to PRD-treated vines sprayed with water only. This supports the idea that the reduction in lateral shoot development seen in PRD-treated vines is due to a reduced production of CKs (Dry et al., 2000a). By measuring shoot growth rate it was found that one common feature of PRD-treated vines, which were not sprayed with CK, was a reduction of lateral shoot growth. It can therefore be speculated that the reduction in lateral growth is related to a reduced delivery of cytokinins from the roots. Zeatin and zeatin riboside concentration in shoot tips and prompt buds/young lateral shoots were reduced by the PRD treatment providing further evidence in support of this hypothesis. Water movement from 'wet' to 'dry' roots Roots, being a primary sensor of soil drying, play an important role in long- and short-term responses to PRD. Using stable isotopes of water and heat-pulse sap flow sensors water movement was traced from wet to dry roots in response to PRD. The redistribution of water from roots grown in a soil of high water potential to roots growing in a soil of low water potential may be of significance with regard to the movement of chemical signals and the control of water balance of roots. Measurements of the relative water content (RWC) have shown a slower decline of RWC of the 'dry' roots of PRD vines relative to roots of vines which received no water, despite similar water content in soil surrounding those roots. The redistribution of water may help to sustain the response to PRD for longer periods possibly releasing chemical signals and to support the activity of fine roots in drying soil. Field vines, irrigated with PRD over several growing seasons, altered their root distribution relative to the control vines. PRD caused a greater concentration of fine roots to grow in deeper soil layers and this may contribute to a better water stress avoidance. The effect on root growth may be augmented by the water movement and by the large difference in ABA to cytokinin ratio, which are also known to alter root growth. PRD makes more efficient use of available water In experiments where both control and PRD-treated vines received the same amount of water many differences between the vines were demonstrated. Under conditions where water supply was adequate for both treatments, the stomatal conductance and growth of the PRD-treated vines was restricted as has been observed in many previous experiments. As total water input was reduced, however, the stomatal conductance of PRD-treated vines became greater than control vines, suggesting that the latter were experiencing a degree of water stress, whereas the PRD-treated vines were not. This may have been due to the greater depth of water penetration in the case of the PRD-treated vines, where water was applied to a smaller soil surface area. This distinction between PRD-treated and control vines, at very low water application rates, was also reflected in pruning weights and crop yields which were actually greater in PRD-treated vines. It was concluded that at low water application rates, the PRD-treated vines were more tolerant of water stress and made more efficient use of available water. Reduction in vigor opens the canopy. The initial aim of the research which led to the development of PRD was to achieve better control of undesirable, excessive shoot and foliage growth which, from a viticultural point of view, has many disadvantages. Grapevine shoot growth rate responds very sensitively to drying soil conditions. The irrigation strategy used in the PRD experiments maintained a reduction of both main shoot and lateral shoot growth. In response to PRD a decrease in shoot growth rate and leaf area was observed. Much of the reduction in canopy biomass was due to a reduced leaf area associated with lateral shoots, thus influencing the canopy structure. This was one major factor improving the light penetration inside the canopy. Control of vegetative vigour results in a better exposure of the bunch zone to light and, as a consequence, in improved grape quality. It is likely that changes in canopy density, as a result of PRD, is causing changes in fruit quality components. Anthocyanin pigments such as derivatives of delphinidin, cyanidin, petunidin and peonidin were more abundant in berries from PRD vines; by comparison the concentration of the major anthocyanin, malvidin, was reduced. When leaves were deliberately removed from more vigorous control vines, which improved bunch exposure, the differences in fruit composition were much reduced. This further supports the idea that a more open canopy, in response to PRD, improves fruit quality by affecting the canopy structure. Fruit quality consequently determines the quality, style and value of the finished wine. Wines from this study have been produced and data on wine quality from commercial wineries are also available. Sensory evaluations have demonstrated that high wine quality from PRD-treated vineyards can be achieved without any yield-depressing effects. This study has provided evidence to support the original hypothesis. The major findings were: a) Chemical signals, altered under PRD and mostly originating from roots, play an important role in the root to shoot communication in grapevines. b) The movement of water from 'wet' to 'dry' soil layers may help to sustain chemical signals as a response of grapevines to PRD and to support the activity of fine roots in drying soil. c) A reduction in vegetative growth, in particular of lateral shoots, was sustained using PRD and affected the canopy structure which in turn, due to a better light penetration into the canopy, improved the fruit quality. d) The reduction in irrigation water applied did not have a detrimental effect on grape yield and thus the efficiency of water use was improved. e) Application of relatively low irrigation rates showed that PRD-treated vines were more tolerant of water stress and made more efficient use of available water.
Thesis (Ph.D.)--Department of Horticulture, Viticulture and Oenology, 2000.

Two experiments were conducted to detect differences in growth and cold hardiness during establishment of northern grown wine grapevines. One experiment tested the use of four grow tube treatments and two pruning levels on vine establishment in the upper Midwest. The variables included leaf area, stem height, root growth, phenology, and hardiness. Overall, few significant differences occurred among treatments where grow tubes were utilized. In the second season, vines without grow tubes had superior measurements in nearly all leaf area categories. For this reason, it is recommended that growers refrain from grow tube use during establishment in northern growing regions. Vines pruned to three buds after transplanting varied little from those without pruning. For this reason, it is recommended that growers utilize the most efficient early pruning strategy for their particular situation. Another experiment was conducted to determine the effectiveness of different weed control measures. This experiment compared three kinds of mulches and an herbicide treatment on the growth and establishment of four wine grape varieties. Annual weed control, plant growth, phenology, soil water content and temperature, and vine hardiness were measured. Overall, vines receiving mulch had more consistent annual weed control and reduced early season growth when compared to chemically treated vines. For this reason, mulch is recommended in the vineyard for annual weed control during establishment in situations where vigor is not unacceptably low.

Thesis (MScAgric)--University of Stellenbosch, 2001.
ENGLISH ABSTRACT: This study is an integral part of a multidisciplinary research project concerning the effects of soil and climate on wine quality. The motive, which led to the setting up of this project, was that producers could not determine beforehand whether a specific location would yield wines of high or low quality. If a specific cultivar were to be planted at the wrong location, then it was likely that wine of table quality would result, rather than the export quality wine that was intended. The long term objectives of this multidisciplinary project were the compilation of guidelines by means of which different sites may be classified according to their potential for the production of high quality wines, and the identification of the most important climatic and soil factors responsible for differences in wine quality and character. In this multidisciplinary project, measurements (soil water, leaf water potential, cane mass and yield) were made under dry land conditions in Sauvignon blanc vineyards at six different localities: five in the Stellenbosch district (Simonsberg, Kuils River, Helshoogte, Papegaaiberg and Devon Valley) and one in Durbanville. Each vineyard was owned by a private commercial producer. The vines were approximately 10 years old in all cases, and were trained on a hedge system. Measurements were made in plots, each of which contained 20 vines. Two different soil types were identified at each locality. Vine growth and wine quality differed markedly on these contrasting soils, even though they were located in close physical proximity. The measurements that were made at high and low production plots at each locality during this study were obtained from points which were not more than 60 m metres apart. An automatic weather station was erected halfway between the two, contrasting, experimental plots. Within the overall scope of the multidisciplinary project, the study which forms the subject of this thesis, concentrated on the effects of soil parent material as a soil forming parameter and as a possible predetermining character with regard to vine growth and wine character. From literature it was clear at the outset of this work that the geology of the coastal wine region is very complex and varies over short distances. The geological history indicates different types of rock formation and rock forming process (sedimentary, igneous as well as metamorphic), plate tectonic activity, mountain building, erosion and weathering, over a period of approximately 1 000 million years. The present landscape includes a coastal plane, hills, and eroding mountains. Statistical analyses indicated that the soils from the different localities could mainly be characterised in terms of differences in their sand size fractions. Soils from Durbanville are dominated by fine sand and correlates with the underlying phyllitic shales. Soils from Kuils River contain significantly more coarse sand when compared with the other sites. This appears to be a reflection of the underlying coarse granitic material, and implies that in situ weathering played an important role in soil development. .The data did not, however, prove that the Kuils River soils formed solely from underlying rocks. The gravel and stone fraction for the Kuils River soils were nevertheless correlated with those of the underlying parent material. Soils from Helshoogte and Simonsberg (both of which are underlain by granites), Papegaaiberg and Devon Valley (both underlain by hornfels) were not significantly dominated by any particular sand fraction. Soils from these localities therefore did not only reflect the underlying material as a source of soil parent material. This implied mixing of parent material and/or the incursion of eolian sand at Helshoogte, Simonsberg and Devon Valley. A marine incursion may have affected the soil parent material at Papegaaiberg. In order to obtain more information concerning the origins and possible mixing of parent materials prior to and during soil formation, samples from the different soil horizons in each profile were subjected to a chemical analysis. Particular emphasis was placed on potassium, which is an extremely important nutrient mineral element, from the viewpoints of vine growth and wine quality. Because the soils used in this study were all located in production vineyards, the probability that fertiliser residues would have contaminated the soils was high. The lower soil horizons were considered to be least affected by this contamination and therefore most likely to be indicative of the natural soil chemical composition. However, the lower horizon K content of the soils in this study could not be reliably correlated with any known or predicted characteristic that might link the soil parent material with local rock types. At Durbanville, both soils contained small quantities of K in the lower horizons, reflecting the underlying phyllitic shales, but at Devon Valley and Papegaaiberg, the lower horizons contained more K than expected. The soils at these localities are situated on hornfels, containing low quantities of K. The large quantities of K in the soils may have indicated that these soils are situated close to a granite/Malmesbury contact zone. Soils from Kuils River, Simonsberg and Helshoogte are situated on K-rich porhyritic granites and it was expected that these soils would contain relatively large quantities of K in the lower horizons. This, however, was not the case. It was therefore concluded that dilution with K-poor material had taken place. Such material could have been derived from higher-lying sandstones, or from eolian processes during the Cenozoic. Alternatively, the K content of the soil might have been depleted by long continued leaching. A semi-quantitative analysis of the minerals in the soil clay fractions was also carried out. The objective was to identify the clay minerals that were present in the different soil horizons and to relate the minerals to weathering conditions. Evidence linking the minerals in the clay fractions of the soil samples with the mineralogical composition of the soil parent materials was sought. The clay fraction mineralogy data indicated that all soils in the study area are in an advanced stage of weathering and are dominated by kaolinite, and in certain soils quartz. It was difficult to relate these minerals directly with soil parent material because the primary minerals originating from the soil parent materials have been extensively broken down. The simultaneous presence of quartz and gibbsite in the clay fraction of both soils at Simonsberg, Helshoogte and Durbanville as well as one soil form from bath Kuils River and Simonsberg, indicated non-uniform distribution of clay fraction minerals, indicating that different stages of weathering were present during soil formation. This could have been a result of mixing of parent materials, but may also reflect different periods of weathering of the same material. Both soils at Papegaaiberg, both soils at Devon Valley and other soils at Simonsberg and Kuils River indicated uniform clay fraction mineralogy distribution, mainly because the absence of gibbsite is related to the presence of quartz in the clay fraction. The soil characteristics, as determined in this study, were also compared with vine growth, wine quality and wine character, as obtained in the broader multidisciplinary research project. For most soils in this study, an increase in clay fraction kaolinite was associated with a reduction in vegetative growth, overall wine quality, and fresh vegetative character. An increase in clay fraction quartz was associated with higher overall wine quality. Increased shoot growth also affected fresh vegetative character positively. Better growth occurred on higher altitudes and this resulted, for Sauvignon blanc, in higher wine quality. Wines produced from vines situated on both phyllitic shales and porhyritic granites showed high quality (Durbanville and Helshoogte), but both were related to low clay fraction kaolinite content and high altitude. It was not possible to relate parent material directly with vine growth, wine quality and/or wine character. The lowest quality wines, however, were produced from vines situated on hornfels (Papegaaiberg and Devon Valley), both containing high quantities of clay fraction kaolinite and situated on low altitudes. High levels of K in soils containing high levels of clay fraction kaolinite may have been partly responsible for low wine quality obtained on such soils.
AFRIKAANSE OPSOMMING: Hierdie studie vorm 'n integrale deel van 'n multi-dissiplinêre navorsingsprojek oor die effek van grond en klimaat op wynkwaliteit. Die motivering wat gelei het tot die beplanning van hierdie projek, was dat produsente nie vooraf kon bepaal of 'n spesifieke lokaliteit wyne kan produseer van hoë of lae kwaliteit nie. Indien 'n spesifieke kultivar op die verkeerde lokaliteit geplant word, sou dit waarskynlik tot In gewone tafelwyn lei, instede van 'n wyn van uitvoergehalte. Die langtermyn doelwitte van die multi-dissiplinêre projek was om riglyne te ontwikkel om verskillende lokaliteite te klassifiseer na aanleiding van·hul potensiaal om hoë kwaliteit wyne te produseer, asook om die belangrikste klimaats- en grondfaktore verantwoordelik vir die produksie van hoê kwalitiet wyne te identifiseer. In hierdie multidissiplinêre projek was metings (plant beskikbare water, blaarwater potensiaal, lootmassa en oes) onder droêland toestande bepaal in Sauvignon blanc wingerde by ses verskillende lokaliteite: vyf in die Stellenbosch distrik (Simonsberg, Kuilsrivier, Helshoogte, Papegaaiberg and Devon Valley) en een in Durbanville. Elke wingerd is besit deur 'n kommersiêle privaatprodusent. Die stokke was ongeveer 10 jaar oud in alle gevalle en opgelei op 'n heining sisteem. Metings was in eksperimentele blokke van 20 stokke elk uitgevoer. Twee verskillende grondtipes is by elke lokaliteit identifiseer. Lootgroei en wynkwaliteit het merkbaar verskilop die kontrasterende gronde, selfs waar gronde nabyaanmekaar was. Die metings is Liitgevoer op hoë- en lae produksie eksperimentele blokke waar gronde by spesifieke lokaliteite nie verder as 60 meter was nie. 'n Outomatiese weerstasie was halfpad tussen die twee kontrasterende grondtipes by elk van die ses lokaliteite opgerig. Binne die algemene omvang van die multi-clissiplinêre projek, het die studie wat die onderwerp van hierdie tesis is, gekonsentreer op die effek van moedermateriaal as grondvormende parameter asook as moontlike voorspeller van wingerdgroei en wynkarakter. Dit was duidelik uit die literatuur dat die geologie van die Wynkusstreek baie kompleks is en oor kort afstande varieer. Die geologiese geskiedenis dui daarop dat verskillende tipes gesteentes en verskillende prosesse van gesteente-vorming (sedimentêr, stollings- en metamorfe), plaattektoniese aktiwiteit, orogenese, erosie en verwering, oor 'n periode van ongeveer 1 000 miljoen jaar plaasgevind het. Die huidige landskap sluit kusvlaktes, heuwels en geêrodeerde berge in. Statistiese analises het aangetoon dat die gronde van die verskillende lokaliteite hoofsaaklik in terme van verskille in sandgrootte fraksies onderskei kon word. Gronde van Durbanville is gedomineer deur fyn sand en korreleer met onderliggende fillietiese skalies. Gronde van Kuilsrivier bevat betekenisvol meer growwe sand wanneer dit vergelyk word met die ander lokaliteite. Dit is waarskynlik afkomstig vanaf die onderliggende growwe granitiese materiaal en impliseer dat in situ verwering 'n belangrike rol gespeel het in grondontwikkeling. Die data het egter nie bewys dat die gronde van Kuilsrivier slegs uit die onderliggende graniete gevorm het nie. Die gruisfraksies in die gronde by Kuilsrivier was tog vergelykbaar met die onderliggende materiaal. Gronde vanaf Helshoogte and Simonsberg (beide onderlê deur graniete), Papegaaiberg and Devon Valley (beide onderlê deur hornfels) was nie betekenisvol gedomineer deur 'n spesifieke sandfraksie nie. Gronde vanaf hierdie lokaliteite het dus nie slegs die onderliggende gesteentes verteenwoordig nie. Dit dui op vermenging van moedermateriaal en/of eoliese prosesse by Helshoogte, Simonsberg and Devon Valley. 'n Styging in seevlak kon die moedermateriaal by Papegaaiberg beïnvloed het. Om meer inligting omtrent die oorsprong en moontlike vermening van moedermateriaal voor grondvorming te verkry, is die verskillende grondmonsters chemies ontleed. Kalium is In uiters belangrike voedingselement wat lootgroei en wynkwaliteit kan beïnvloed. Aangesien die gronde in hierdie studie in bestaande produksieblokke voorkom, was daar 'n goeie kans dat bemestingstowwe die chemiese samestelling kon beïnvloed. Die C horisonte van die verskillende gronde was beskou as dié wat die minste deur bemesting beYnvloedsou word en die naaste aanduiding van natuurlike grondchemiese samestelling. Die C horison K-inhoude van die gronde in die studie het egter nie gekorreleer met enige eienskap wat die moedermateriaal van die gronde met die lokale gesteentetipe kon verbind nie. By Durbanville, het beide gronde klein hoeveelhede K in die C horisonte bevat, wat die onderliggende fillietiese skalies reflekteer, maar by Devon Valley en Papegaaiberg, het die C horisonte meer K bevat as wat verwag is. Die gronde by hierdie lokaliteite word onderlê deur hornfels, wat lae hoeveelhede K bevat. Die groot hoeveelhede K in hierdie gronde dui moontlik op 'n kontaksone tussen graniet en Malmesbury gesteentes in die area. Gronde vanaf Kuilsrivier, Simonsberg en Helshoogte word onderlê deur K-ryke porfiritiese graniete wat groot hoeveelhede K in die ondergronde sou bevat. Dit was egter nie die geval nie en dit was aanvaar dat verdunning van K-arme materiaal plaasgevind het. Die oorsprong van Karme materiaal was waarskynlik vanaf hoêr-liggende sandstene, of vanaf eoliese prosesse gedurende die Cenozoikum. Alternatiewelik is K inhoude van die gronde verlaag deur lang en aanhoudende loging. 'n Semi-kwantitatiewe analise van minerale in die kleifraksie was uitgevoer om te bepaal watter minerale in die kleifraksie van die verskillende gronde teenwoordig is en om die minerale met stadia van verwering te vergelyk. Dan kon die mineralogiese samestelling in verband met moedermateriaal gebring word. Resultate het aangetoon dat al die gronde in die studie in 'n gevorderde stadium van verwering is en gedomineer word deur kaoliniet, en in sekere gronde, klei fraksie kwarts. Aangesien die primêre minerale in 'n groot mate afgebreek is, was dit moeilik om die minerale in die kleifraksie direk in verband met moedermateriaal te bring. Die voorkoms van kwarts en gibbsiet in die kleifraksie in beide gronde van Simonsberg, Helshoogte en Durbanville asook een grondvorm vanaf beide Kuilsrivier en Simonsberg, het aangetoon dat verskillende stadia van verwering gedurende grondvorming in hierdie gronde voorgekom het. Dit kan die gevolg wees van vermenging van verskillende moedermateriaal, maar kan ook verskillende periodes van verwering van dieselfde materiaal aandui. Beide gronde by Papegaaiberg, beide gronde van Devon Valley die ander gronde by Simonsberg en Kuilsrivier het slegs een fase van verwering tydens grondvorming aangedui, hoofsaaklik as gevolg van die afwesigheid van gibbsiet wanneer kwarts voorkom. Grondeienskappe, soos bepaal in hierdie studie, was ook vergelyk met lootgroei, wynkwaliteit en wynkarakter, soos verkry uit die resultate van die multi-dissiplinêre projek. Vir die meeste gronde in die studie was 'n toename in kleifraksie kaoliniet geassosieer met afname in vegetatiewe groei, algemene wynkwaliteit, asook vars vegetatiewe wynkarakter. 'n Toename in kleifraksie kwarts was geassosieer met hoër algehele wynkwaliteit. 'n Toeneme in vegetatiewe groei het ook die vars vegetatiewe karakter van die wyn positief beïnvloed. Beter vegetatiewe groei het op hoër hoogtes voorgekom en dit het gelei tot hoër wynkwaliteit vir Sauvignon blanc. Wyne afkomstig van wingerde op beide fillietiese skalies en porfiritiese graniete, was van hoër kwaliteit (Durbanville and Helshoogte), maar beide was geassosieer met lae kleifraksie kaoliniet en hoë ligging. Dit was nie moontlik om moedermateriaal direk met vegetatiewe groei, wynkwaliteit en/of wynkarakter te vergelyk nie. Wyne met die laagste kwaliteit kom egter voor op hornfels (Papegaaiberg and Devon Valley), wat beide groot hoeveelhede kleifraksie kaoliniet bevat en geleê is op lae hoogtes. Hoê vlakke van K in gronde wat groot hoeveelhede kleifraksie kaoliniet bevat kan gedeeltelik verantwoordelik wees vir lae kwaliteit wyne op sulke gronde.

Bibliography: leaves 127-152. The aim of this work is to study viroids in grapevines, particularly their vertical transmission via seeds, during meristem culture and micropropagation. There was also an attempt to produce viroid-free vines by shoot apical meristem culture (SAMC).

In this thesis, I intend to present an original costume design for John Steinbeck's The Grapes of Wrath. This production is the first full collaboration of its kind between Virginia Commonwealth University’s Theatre Department and Barksdale Theatre. This thesis will be a complete account of my entire design process from the design concept to the finished, realized production. I will be examining my design choices and finished production photos, including color photographs of my original renderings, fabric swatches and research. Throughout my thesis, I will be researching ways to accurately represent the millions of exploited itinerant farm laborers who survived the severe drought and economic depression of the early 1930s.

This thesis presents a systematic investigation of bacterial species associated with wine grapes cultivated in Australian vineyards during 2001-2004. Grapes, sampled throughout cultivation, were analysed for bacterial species using a combination of cultural and molecular methods. Red (Shiraz, Cabernet Sauvignon, Merlot) and white (Chardonnay, Semillon, Sauvignon Blanc) grape varieties were examined. Factors affecting the bacterial ecology of grapes were considered. The bacterial populations of mature undamaged grapes at harvest were consistently low at 102-103 CFU/g. Higher populations (103-106 CFU/g) were found on grapes at earlier stages of maturity and correlated with application of Bacillus thuringiensis as a biological pesticide. B. thuringiensis was the most prevalent bacterial species on wine grapes throughout cultivation, as determined by plate culture, enrichment culture and PCR-DGGE. B. thuringiensis carried over into wine processing but did not grow in juice or wine and did not adversely affect the growth of Saccharomyces cerevisiae or Oenococcus oeni in liquid culture. B. thuringiensis inhibited the growth of several spoilage and mycotoxigenic fungi found on grapes. Curtobacterium flaccumfaciens was the second most prevalent species detected on wine grapes. Its populations rarely exceeded 103-104 CFU/g. Other bacteria (Arthrobacter, Bacillus, Microbacterium, Pantoea, Pseudomonas, Sphingomonas) were sporadically found on grapes. Lactic acid bacteria and acetic acid bacteria were rarely detected on undamaged grapes by culture and PCR-DGGE methods. A greater incidence of lactic acid bacteria was detected by specific enrichment procedures, especially on damaged grape berries. Species found were Lactobacillus plantarum, Lactobacillus mali, Lactobacillus lindneri and Lactobacillus kunkeei. The malolactic organism, O. oeni, was never isolated from any grape sample, raising questions about its enological origin. Enrichment cultures also revealed the presence of other bacteria (e.g. Sporolactobacillus inulinus, Asaia siamensis) not previously found on wine grapes. Atypical, hot and dry conditions during cultivation may account for the low populations of bacteria found on wine grapes. This factor combined with the overwhelming presence of B. thuringiensis prevented meaningful comparisons of data to determine influences of vineyard location, grape variety, grape maturity, climate and viticultural practices on the bacterial ecology of grapes. More systematic and controlled studies of these variables are required.

Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: The cultivation of table grapes in the warmer areas of South Africa, indeed worldwide, is complicated by rest breaking problems in spring due to delayed budbreak. In order to overcome these problems rest breaking agents, mainly hydrogen cyanamide, are applied. However, instead of alleviating the problem, additional problems such as uneven budbreak and reduced production are often induced. This study was initiated to further understand the physiological processes occurring during budbreak and how the application of hydrogen cyanamide influences these processes. The following aspects were investigated in this study: a. The effect of hydrogen cyanamide on tissue cytokinin (specifically zeatin riboside) levels of Sultanina table grape vines after application at different times before natural budbreak was studied over two seasons. In 1997, hydrogen cyanamide was applied at three weeks before induced budbreak and in 1998 at six weeks before induced budbreak. One year-old canes were sampled weekly after hydrogen cyanamide application, divided into distal and proximal sections, then further divided into buds, bark and wood tissues and the zeatin riboside (ZR) levels determined. A relatively high amount of chilling coupled to late hydrogen cyanamide application in 1997 led to a large effect on ZR release, but did not lead to significant shifting of the budbreak pattern. Zeatin riboside peaks were observed in buds, internode wood and bark of treated vines compared to control vines. The peaks were higher in distal portions compared to proximal portions in all tissues. The relatively lower chilling and earlier application of hydrogen cyanamide in 1998 had a larger effect on the budbreak pattern while the bud ZR peak was shifted earlier. The distal portion bud ZR . peak was again higher than the proximal portion bud ZR peak. In 1997, as sampling was not initiated early enough, bud ZR peaks were only observed after budbreak, while in 1998 bud ZR peaks were observed before and after budbreak. The effect of these ZR increases on the development of inflorescence primordia, subsequent bunch development and ultimately production, are discussed. b. Free xylem sap was sampled at cane and spur pruned lengths from unpruned canes of Sultanina from budswell until after budbreak in 1999 and from three table grape cultivars, i.e Sultanina, Alphonse Lavalleé and Sunred Seedless, in 2001 and ZR levels determined. The ZR levels in the buds of these three table grape cultivars, pruned to different cane lengths were also determined. One year old canes of these cultivars, were each pruned to long canes (14 buds) and short spurs (2 buds). The ZR content in buds of these canes at distal and proximal positions were determined weekly from budswell until after budbreak in 1999. Xylary ZR peaks occurred before 50% budbreak. Spur xylary ZR levels of all three cultivars followed a similar pattern, although at lower ZR levels than that of the canes. This is similar to previous studies on xylary ZR levels of apple shoots. The high levels of free ZR found in xylem sap at the distal portions of canes support the hypothesis of a cumulative ZR build-up effect as cane length increases. Spur pruning resulted in earlier budbreak and a higher final budbreak than cane pruning. The proximal portions of shoots, whether spur pruned or the proximal portions of canes, showed elevated ZR levels in all cultivars. This difference in ZR levels in bud tissue of different portions of the cane would suggest a difference in ZR consumption or turnover. The results of this study have important management implications for the cultivation of vines in warmer areas in which hydrogen cyanamide is used to alleviate budbreak problems.
AFRIKAANSE OPSOMMING: Die verbouing van tafeldruiwe in die warmer gebiede van Suid-Afrika, soos straks wêreldwyd, word bemoeilik deur rusbreekprobleme in die lente weens vertraagde bot. Rusbreekmiddels, meestal waterstofsiaanamied, word gevolglik toegedien om hierdie probleme te probeer oorkom. In plaas van opheffing van die probleem, veroorsaak hierdie toedienings somtyds addisionele probleme soos ongelyke bot en verlaagde produksie. Hierdie studie is aangepak om die fisiologiese prosesse wat tydens bot plaasvind, beter te verstaan, asook hoe die toediening van waterstofsiaanamied hierdie prosesse beïnvloed. Die volgende is in hierdie studie ondersoek: a. Die invloed van waterstofsiaanamied op lootweefsel sitokinien (naamlik zeatin ribosied, ZR) vlakke van 'n Sultanina tafeldruif wingerd is oor twee seisoene ondersoek na toediening op verskillende tye voor bot. Waterstofsiaanamied is in 1997 drie weke en in 1998 ses weke voor geïnduseerde bot toegedien. Een jaar oue lote is weekliks gemonster na waterstofsiaanamied toediening, verdeel in apikale en basale gedeeltes en verder verdeel in ogies, bas en houtweefsel en die ZR vlakke bepaal. Relatief hoër vlakke koue, gekoppel met later watersiaanamied toediening het in 1997 tot 'n groot effek op ZR vlakke gelei, maar het nie die botpatroon wesentlik verskuif nie. Zeatin ribosied pieke is waargeneem in ogies, internode hout en bas van behandelde wingerd in vergelyking met kontrole wingerd. Die pieke was hoër in apikale gedeeltes in vergelyking met basale gedeeltes in alle weefsels. Die relatief laer koue en vroeër toediening van waterstofsiaanamied in 1998 het 'n groter effek op die botpatroon gehad, terwyl die ogie ZR piek vroeër geskuif is. Die apikale gedeelte se ogie ZR piek was weereens hoër as die basale gedeelte se ogie ZR piek. Monstering was nie vroeg genoeg begin in 1997 nie, aangesien ogie ZR pieke slegs na bot waargeneem is, terwylogie ZR pieke in 1998 voor en na bot waargeneem is. Die effek van hierdie verhoging in ZR vlakke op die ontwikkeling van blom primordia, daaropvolgende tros ontwikkeling en uiteindelik produksie, is bespreek. b. Vry xileemsap is gemonster van langdraer en kortdraer gedeeltes van ongesnoeide lote van Sultanina vanaf ogieswel tot na bot in 1999 en vanaf drie tafeldruif kultivars, naamlik Sultanina, Alphonse lavalleé en Sunred Seedless, in 2001 en die ZR vlakke bepaal. Die ZR vlakke van ogies van hierdie drie kultivars, gesnoei tot verskillende lootlengtes is ook bepaal. Eenjarige lote van hierdie kultivars is gesnoei tot langdraers (14 ogies) en kortdraers (2 ogies). Die ZR vlakke in ogies geleë op apikale en basale gedeeltes van hierdie lote is weekliks in 1999 bepaal vanaf ogieswel tot na bot Xileemsap ZR pieke is waargeneem voor 50% bot. Kortdraer xileemsap ZR vlakke het 'n soortgelyke patroon as die langdraers gevolg vir al drie kultivars, alhoewel teen laer ZR vlakke as die langdraers. Hierdie waarneming is soortgelyk aan vorige studies op xileemsap ZR vlakke van appel lote. Die hoë ZR vlakke gevind in die xileemsap van die apikale gedeeltes van lote ondersteun die hipotese van 'n kumulatiewe opbou van ZR soos die lengte van die loot toeneem. Die snoei van lote as kortdraers het gelei tot vroeër bot en 'n hoër finale bot persentasie as die snoei van langdraers. Die basale gedeeltes van lote het verhoogde ZR vlakke in al drie kultivars getoon, onafhanklik van die feit dat dit vanaf die kortdraer of die basale gedeelte van 'n langdraer was. Hierdie verskil in ZR vlakke in ogie weefsel van verskillende gedeeltes van die loot impliseer 'n verskil in ZR verbruik of omset. The resultate van hierdie studie het belangrike bestuursimplikasies vir die verbouing van wingerd in warmer gebiede, waar waterstofsiaanamied gebruik word om botprobleme te oorkom.

Thesis (MScAgric) -- University of Stellenbosch, 2000.
ENGLISH ABSTRACT: Postharvest berry split and abscission are prevailing physiological disorders that negatively impact on the quality of table grapes exported from South Africa. Inferior grape quality due to these disorders results in a considerable decline in consumer confidence in the branded product, which leads to a drop in demand, and consequently, lower prices. Since information concerning postharvest factors influencing postharvest berry split and abscission is limited, the search for reliable methods to adequately control these problems remains elusive. In an attempt to obtain the required information, the influence of harvest temperature, harvest maturity, perforated liners, field heat removal prior to packing, delay periods before and after packing, storage duration and the elevation of storage temperature on the development of berry split and abscission in 'Thompson Seedless' (Vitis vinifera Linnaeus) table grapes was investigated. Changes in abscission related factors during berry development, and the influence of pre-and postharvest ethylene inhibitors on the development of berry abscission in 'Waltham Cross' table grapes, was also studied. Berry split was aggravated by packing 'Thompson Seedless' grapes at high pulp temperatures of approximately 30°C, especially if the grapes were packed in non-perforated bags. The incidence of berry split could be reduced by between 80 and 90% by packing grapes in perforated instead of non-perforated liners. Perforated bags also reduced levels of S02 damage. However, due to significantly more moisture loss from grapes in perforated bags, compared to non-perforated bags, the risk of higher fruit and stem desiccation and softer berries existed. Optimum size and density of perforations needs to be determined to reduce berry split without excessive loss of moisture from the grapes, and S02gas from the air space surrounding the product. The influence of harvest temperature and liner type on berry abscission was not conclusive. Advanced maturity increased grape resistance to berry split. However, grapes harvested too mature were prone to stem desiccation and the development of Botrytis decay. The occurrence of berry abscission also appeared to increase with advanced harvest maturity. Consequently, to ensure optimal post-storage quality, 'Thompson Seedless' grapes should be harvested as soon as horticultural maturity has been reached, which appears to be at approximately 18°Brix. Field heat removal for 1.5 hours at 19°C prior to packing had no beneficial or adverse effect on berry split and abscission. Delay periods prior to packing aggravated berry abscission, but did not influence berry split significantly. Grapes delayed for 12 hours showed a significant increase in berry abscission and Botrytis decay, compared to grapes delayed for only 3 or 8 hours. Considering that the absence of fungal decay is the most important quality prerequisite in table grapes, it is of vital importance to pack grapes with as short a delay period as possible. Grapes packed in non-perforated liners and delayed for different durations after packing, before the onset of forced-air cooling (FAC), showed significant differences regarding the incidence of berry split. Grapes delayed for 18 hours had significantly higher levels of berry split directly after the delay period, compared to grapes delayed for 6 or 12 hours. No significant difference in berry abscission occurred between grapes delayed for different periods. To minimise the amount of berry split, FAC should be applied as rapidly as possible after the packing of grapes in non-perforated liners. Two storage related factors significantly influenced the incidence of berry split in 'Thompson Seedless' grapes during cold storage significantly, viz. the duration of storage at -O.soC,and the increase in temperature after low temperature storage. Berry split increased almost linearly with prolonged storage at -O.soC. An elevation of storage temperature from -O.soC to 10°C any time during the cold storage period, further aggravated the split problem. Consequently, the reduction of berry split in 'Thompson Seedless' table grapes during cold storage requires (a) the shortest possible cold storage period, and (b) good temperature management throughout distribution, from initiation of cooling until the final point of sale. The grape berry abscission potential, as quantitatively indexed by the measurement of the fruit removal force (FRF), showed significant changes during berry development of 'Waltham Cross' table grapes, from 27 to 111 days after full bloom (OAFB). This showed that at certain stages of fruit growth, 'Waltham Cross' grapes are more prone to berry abscission. At 27 OAFB, when the berries had an average diameter of 6.6mm, the grape bunches showed a significantly higher potential for berry abscission, compared to grapes sampled at a later stage. 'Waltham Cross' has inherently straggly bunches with bare shoulders. Therefore, any abscission during berry development will aggravate the problem. Consequently, it is of vital importance that any adverse factors such as moisture stress be avoided, especially during the period when 'Waltham Cross' grapes appear to be very susceptible to berry abscission. Of all parameters measured, moisture loss showed the best correlation with abscission. Grapes harvested with total soluble solids (TSS) of 12.3°Brix, 83 OAFB, had a significantly higher abscission potential than grapes harvested more mature. Therefore, by harvesting 'Waltham Cross' grapes at optimum maturity, at a TSS of approximately 16.4°Brix, berry abscission can be reduced to a great extent. It was evident that at veraison, the metabolism of grape berries changes drastically, and additional to the rapid increase in sugars and the rapid decrease in acidity, a decrease in FRF occurs. Preharvest sprays of ReTain™ (a derivative of aminoethoxyvinylglycine), which inhibits ethylene synthesis, showed no promise as a means to reduce postharvest berry abscission. A postharvest treatment with EthylBloc® (1-methylcyclopropene), which inhibits ethylene action, only reduced berry abscission during one season.
AFRIKAANSE OPSOMMING: Die fisiologiese defekte korrelbars en los korrels wat algemeen voorkom tydens opberging van sekere tafeldruif-kultivars, het 'n negatiewe invloed op tafeldruiwe wat uitgevoer word vanaf Suid-Afrika. Minderwaardige kwaliteit as gevolg van hierdie defekte het 'n aansienlike afname in verbruikers-vertroue tot gevolg wat aanleiding gee tot 'n ooreenkomstige afname in aanvraag en prys van die produk. Inligting rakende na-oes faktore wat die voorkoms van korrelbars en los korrels beïnvloed is beperk, en geen gewaarborgde metode bestaan om hierdie twee defekte volkome te beheer nie. In 'n poging om dié gewenste inligting te bekom, is ondersoek ingestel na die effek van oes-temperatuur, oes-rypheid, geperforeerde sakke, veldhitte verwydering voor verpakking, vertragingsperiodes voor en na verpakking, tydsduur van opberging, en die verhoging van die opbergingstemperatuur, op die voorkoms van korrelbars en los korrels by 'Thompson Seedless' (Vitis vinifera Linnaeus) druiwe. Daar is ook ondersoek ingestel na veranderings in afsnoering verwante faktore tydens korrel-ontwikkeling, en die invloed van vooren na-oes toedienings van etileen inhibeerders op die ontwikkeling van los korrels by 'Waltham Cross'tafeldruiwe. Korrelbars is vererger deur 'Thompson Seedless' met hoë pulptemperature van ongeveer 29.5°C te verpak, veral indien dit in 'n riie-geperforeerde sak verpak is. Die voorkoms van korrelbars kon tussen 80 en 90% verminder word deur 'Thompson Seedless' druiwe in geperforeerde sakke te verpak, in plaas van nie-geperforeerde sakke. Geperforeerde sakke het ook S02 skade op die druiwe verminder. Tog, as gevolg van betekenisvol meer vogverlies vanaf druiwe in geperforeerde sakke as vanaf druiwe in nie-geperforeerde sakke, bestaan die risiko van meer stingel-uitdroging en minder ferm korrels indien druiwe in geperforeerde sakke verpak word. Optimale grootte en digtheid van perforasies moet bepaal word om korrelbars te verminder, maar sonder oormatige vogverlies vanaf die druiwe en oormatige verlies aan S02. Die invloed van oes-temperatuur en sak-tipe op los korrels was nie oortuigend nie. Gevorderde oes-rypheid het die druif se weerstand teen korrelbars verhoog. Daarteenoor was druiwe wat té ryp geoes is, meer gevoelig vir stingel-uitdroging en Botrytis bederf. Dit wilook voorkom of die voorkoms van los korrels toeneem met gevorderde rypheid. Dus, om optimum kwaliteit na opberging te verseker, moet 'Thompson Seedless' geoes word sodra hortologiese rypheid bereik word, wat blyk om by 'n totale opgeloste vaste stof-inhoud (TOVS) van ongeveer 18°Brix te wees. Veldhitte verwydering voor verpakking, vir 1.5 uur by 19°C, het geen effek gehad op die voorkoms van korrelbars en los korrels nie. 'n Vertragingsperiode voor verpakking het die los korrel-probleem vererger, alhoewel dit geen betekenisvolle invloed op die voorkoms van korrelbars gehad het nie. Druiwe wat vir 12 uur voor verpakking vertraag is, het betekenisvol meer los korrels en Botrytis bederf getoon, in vergelyking met druiwe wat slegs 'n vertragingsperiode van 3 of 8 uur ondergaan het. Aangesien die afwesigheid van bederf die belangrikste kwaliteits-vereiste vir tafeldruiwe is, is dit van kardinale belang om druiwe so gou as moontlik na oes te verpak. Druiwe, verpak in nie-geperforeerde sakke, wat vir verskillende periodes vertraag is voor geforseerde-lug verkoeling, het betekenisvolle verskille getoon betreffende die voorkoms van korrelbars. Druiwe vertraag vir 18 ure voor verkoeling, het betekenisvol meer korrelbars getoon, soos gemeet onmiddellik na die vertragingsperiode, in vergelyking met druiwe wat slegs vir 6 of 12 ure vertraag was. Geen betekenisvolle verskille in los korrels het voorgekom tussen druiwe wat verskillende vertragingsperiodes ondergaan het nie. Om korrelbars te verminder, moet geforseerde-lug verkoeling so gou as moontlik na verpakking van druiwe in nie-geperforeerde sakke toegepas word. Twee opbergings-verwante faktore beïnvloed die voorkoms van korrelbars by 'Thompson Seedless' druiwe tydens koelopberging, naamlik die tydsduur van opberging by -O.soC,asook 'n styging in temperatuur vanaf -O.soC tot 1DoC. Korrelbars het feitlik liniêr toegeneem met verlengde opberging by -O.soC. 'n Styging in temperatuur vanaf -O.SoCtot 1DoCop enige tydstip gedurende die koelopbergingsperiode, het korrelbars verder vererger. Dus, om korrelbars by 'Thompson Seedless' tydens opberging tot die minimum te beperk, moet die tydsduur van opberging so kort as moontlik wees, en moet die koue ketting regdeur die distribusie-proses gehandhaaf word, vanaf inisiëring van verkoeling tot en met die uiteindelike verkoop van die produk. Die afsnoerings-potensiaal van druiwe, soos kwantitatief geïndekseer is deur meting van die vrug-verwyderings-vermoë (VVV), het betekenisvol verander gedurende korrel-ontwikkeling van 'Waltham Cross' tafeldruiwe, vanaf 27 tot 111 dae na volblom (DNVB). Dit het getoon dat 'Waltham Cross' druiwe by sekere stadiums van vrug-groei meer gevoelig is vir korrel afsnoering. By 27 DNVB, wanneer die korrels 'n gemiddelde deursnee van 6.6mm gehad het, het die druiwe 'n betekenisvolle hoër potensiaal vir afsnoering getoon, in vergelyking met druiwe wat op 'n latere stadium getoets is. 'Waltham Cross' is inherent geneig tot yl trosse met kaal skouers, gevolglik sal enige afsnoering tydens korrel-ontwikkeling die probleem vererger. Dus is dit van kardinale belang dat enige nadelige faktor, soos byvoorbeeld vogstres, vermy moet word, veral gedurende periodes wanneer dit wil voorkom of 'Waltham Cross' baie vatbaar is vir korrel afsnoering. Van al die parameters wat gemeet is, het vogverlies die beste korrelasie met korrel afsnoering getoon. Druiwe wat 83 DNVB, by 'n TOVS van 12.3°Brix geoes is, het 'n betekenisvol hoër potensiaal vir korrel afsnoering getoon, in vergelyking met druiwe wat ryper geoes is. Dus, deur 'Waltham Cross' druiwe by optimum rypheid te oes, by 'n TOVS van ongeveer 16.4°Brix, kan korrelbars in 'n groot mate verminder word. Tydens verelson, wanneer die metabolisme van die druiwe drasties verander, was daar gepaardgaande met die drastiese toename in TOVS en die drastiese afname in totale titreerbare sure (TSS), ook 'n afname in Voor-oes bespuitings met ReTain™, wat etileen sintese inhibeer, het geen potensiaal getoon om los korrels by 'Waltham Cross' te verminder nie. 'n Na-oes behandeling met EthyIBloc®, wat etileen werking inhibeer, het slegs korrel afsnoering in een van die seisoene effens verminder.

Doutoramento em Engenharia Alimentar - Instituto Superior de Agronomia
The grape berry microbiota is deeply influenced by the sanitary status of grapes. In sound grapes the most frequent yeast species were basidiomycetes, Aureobasidium pullulans, Candida zemplinina and Hanseniaspora uvarum. Sour rotten grapes were mostly colonised by C. zemplinina, H. uvarum, Issatchenkia spp. and Zygoascus hellenicus. The presence of minoritary populations of Zygosaccharomyces bailii was only found in damaged grapes. The acetic acid bacteria Gluconobacter spp. and Gluconoacetobacter spp. were isolated from healthy and injured grapes, while Acetobacter spp. was only associated with sour rot. Sour rot induced an increase of the sugar content, volatile acidity, colour and total phenols of grape juices. Wines with sour rot up to 30% showed equal overall quality after one year of bottle storage. However, wines made with sour rotten grapes showed a distinctive chemical and honey-like aroma. Phenylacetic acid and ethyl phenylacetate, both exhibiting honey-sweet like aromas, emerged as key-aroma compounds of sour rotten wines. The causal agents of sour rot were acetic acid bacteria disseminated by the insect Drosophila spp.. In the absence of these flies, putative plant defense mechanisms, probably mediated by the accumulation of phenylacetic acid, led to skin healing, preventing sour rot spreading

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.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011.
ENGLISH ABSTRACT: The removal of grape berries from the stems is an important step in the wine making process. Various problems are experienced using the destemming machines currently available, where the berries are mechanically removed and separated from the stems by a rotating beater shaft and drum. Not all berries are removed from the stems and broken stems can end up with the removed berries which can result in unwanted characters and flavours in the wine. The development of these machines is currently limited to experimental tests. In this study, the destemming process was investigated experimentally. The ability of the Discrete Element Method (DEM) to simulate this process was also investigated. A range of experiments was designed to obtain the material properties of the grapes. These experiments included the measurement of the stem stiffness and break strength, the berry stiffness, and the force needed to remove a berry from the stem. Experiments were conducted to gain further insight into the destemming process. Firstly, a simplified destemming machine with only a beater shaft and a single grape bunch was built. The influence of the bunch size and the speed of the beater shaft on the number of berries removed from the stems were investigated. Secondly, field tests on a commercial destemming machine were conducted and the performance of the machine was measured. A DEM model of both the simplified and the commercial destemming machine were built. Commercial DEM software was used with linear contact and bond models. The stems were built from spherical particles bonded together and a single spherical particle was used to represent each berry. The measured stiffnesses and break strengths were used to set the particle and bond properties. Modelling the simplified destemming machine, it was found that the DEM model could accurately predict the effect of the bunch size and the speed of the beater shaft on the number of berries removed from the stems. The model of the commercial destemming machine could accurately predict the machine’s performance in terms of the number of berries removed as well as the number of broken stems.
AFRIKAANSE OPSOMMING: Die verwydering van druiwekorrels vanaf die stingels is ʼn belangrike stap tydens die wynmaak proses. Verskeie probleme word ondervind met huidige beskikbare ontstingelaars, waar die korrels meganies verwyder en skei word vanaf die stingels deur middel van ʼn roterende klop-as en drom. Nie alle korrels word vanaf die stingels verwyder nie en gebreekte stingels kan saam met die verwyderde korrels beland, wat ongewensde karakters en geure in die wyn kan veroorsaak. Die ontwikkeling van ontstingelaars is tans beperk tot eksperimentele toetse. In hierdie studie is die ontstingel proses eksperimenteel ondersoek Die vermoë van die Diskrete Element Metode (DEM) om hierdie proses te simuleer is ook ondersoek. ʼn Reeks eksperimente is ontwikkel om die materiaal eienskappe van die druiwe te bepaal. Hierdie eksperimente sluit in die meet van die styfheid en breeksterkte van die stingel, die korrel styfheid, en die krag benodig om ʼn korrel vanaf die stingel te verwyder. Eksperimente is gedoen om verdere insig oor die ontstingel proses te bekom. Eerstens is ʼn vereenvoudigde ontstingelaar gebou, met slegs ʼn klop-as en een tros. Die invloed van die trosgrootte en die klop-as spoed op die aantal korrels wat verwyder is, is ondersoek. Tweedens is ʼn toets in die veld gedoen met ʼn kommersiële ontstingelaar om die werkverrigting van die masjien te bepaal. ʼn DEM model van beide die vereenvoudigde en kommersiële ontstingelaar is gebou. Kommersiële DEM sagteware is gebruik met lineêre kontak- en bindingsmodelle. Die stingels is gebou deur sferiese partikels aan mekaar te bind en ʼn enkele sferiese partikel is gebruik om ʼn druiwe korrel voor te stel. Die gemete styfhede en breeksterktes is gebruik om die partikel- en bindingseienskappe te spesifiseer. Die modellering van die vereenvoudigde ontstingelaar het getoon dat die DEM model akkuraat kan voorspel wat die invloed is van die trosgrootte en die klop-as spoed op die aantal korrels wat verwyder is. Die model van die kommersiële ontstingelaar kon die werkverrigting van die masjien akkuraat voorspel in terme van die aantal korrels wat verwyder is asook die aantal gebreekte stingels.

Word processed copy.|Bibliography: leaves 64-66.
This thesis acts as a series of 'snapshots' into the meaning of 'wine tourism'. Each chapter of my main body of work looks at a different segment of wine tourism in the Western Cape: a fast growing industry that inherits attributes from both the wine and tourism industries. Themes of landscape and the tourist experience track through these separate snapshots, linking them together. A passion for wine and the drinking of wine would seem to have been an enjoyable pastime passed down from epochs of wine lovers and producers that stood before us in the 'winescapes' of time. While this conception of the wine drinking tradition may be presented to us today, it should be remembered that this might not have been the case in times gone by. Looking back to South Africa and the wine industry in the 1950s where 'wine consciousness' was a real concern for the marketers and makers of wine, we find no such traditions in place. Obstacles to the integration of wine into everyday living came in the form of an avid temperance movement concerned with drunkenness and alcoholism. Over time these obstacles heeded to the power of the wine industry so that increasing emphasis was placed on the role of publicity and marketing of wine. It was perhaps a natural development that wine tourism came to hold particular potential and interest for South African wine producers. The history of wine tourism of the Western Cape is inherently connected to the establishment of our first wine route in Stellenbosch. With a concern for the superiority of the European wine making tradition and landscape, it was only in 1970 that we saw a change in interest to the wine regions and heritage landscapes of our own country. The SteHenbosch wine route was a concept inspired by European example but grounded in local landscape. The significance of the mapping out of this landscape of space into place was a real concern for the wine makers of the regions whose freedom to market and export their wine overseas was severely restricted by legal prohibitions established by the KWV in the 1960s. With the defining of distinct wine regions, came the emphasis of difference of place within the winelands of the Western Cape. Each region has a formula for difference based on some combination of breathtaking scenery, quality wines, first class cuisine, and with increasing frequency the heritage of European roots. The construction of place and landscape identities gives us a sense of the perspective of the marketer and promoter of the wine region. I found it important to explore how this construction of identity of place came to be experienced by and presented to tourists in the present day.