Dissertationen: „Fusarium pathogens“

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Vágány, Viktória. „Characterisation of fusarium pathogens in the UK“. Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/56393/.

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The primary aim of this project was to identify and characterise Fusarium species associated with the basal rot of Allium species and internal fruit rot of sweet peppers in the UK. The secondary objective was to develop quick molecular markers to identify Fusarium oxysporum f. sp. cepae (FOC) causing onion basal rot. Isolates representing diverse Fusarium species taken from onions, garlic, shallot and leeks obtained from different production and processing sites in the UK were collected. F. proliferatum was found for the first time to be a causal agent of onion basal rot in the UK, but F. oxysporum was by far the most common species and F. oxysporum isolates belonged to at least two different genotypes based on a sequence comparison of several “housekeeping” genes, and overall, appeared to be polyphyletic. None of the housekeeping genes studied correlate with pathogenicity. Secreted in xylem (SIX) genes offer more promise for the specific identification of F. oxysporum formae speciales (Lievens et al., 2009a) and a homologue of the SIX7 gene was found only in a few FOC isolates suggesting that SIX7 is not absolutely necessary for pathogenicity. Whole genome sequencing of a FOC isolate was carried out in order to understand pathogenicity and identify novel effector genes. This work revealed the presence of further homologues of published SIX genes, namely SIX3, SIX5 and SIX9. The presence of SIX3 and SIX5 has only been reported from F. oxysporum f. sp. lycopersici previously. Additionally, screening of eleven new candidate effector genes suggested that FOC isolates have different gene sets which correspond to the continuous variation of aggressiveness found within the FOC population. Fusarium lactis, F. proliferatum and F. solani were identified in association with internal fruit rot of sweet pepper obtained from three different production sites in the UK.

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Almiman, Bandar F. „Molecular genetic and genomic characterization of an emerging mycotoxigenic pathogen Fusarium proliferatum“. Thesis, University of Bedfordshire, 2018. http://hdl.handle.net/10547/622835.

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This aim of this research was to elucidate the genotypic diversity of the mycotoxigenic species Fusarium proliferatum associated with diverse hosts and distributed in wide geographic locations to gain new insights into the biology of this emerging pathogen. This study developed a novel molecular genetic marker FG1056. Multilocus typing of F. proliferatum isolates (52) using F. verticillioides (2) and F. oxysporum (3) as references was carried out with FG1056 and a set of known genetic markers (ITS, TEF1, CAL and FUM1). This distinguished up to 10 genetic groups, 2 clusters and 23 haplotypes among the F. proliferatum isolates. FG1056 marker showed the highest number of SNPs (169), informative sites (89) and haplotypes (23) relative to other markers used and was comparable to the multi locus typing. Varying patterns of relationships were observed between isolates represented in the genetic groups and their host and geographic origin. Considerable biological variability was recorded among the F. proliferatum isolates in morphology, growth, sporulation and most notably fumonisin production (up to 140-fold differences) with reference to variable temperature, water activity and duration. De novo genome assemblies with the size ranging from 43.96 - 50 Mb have been developed for four diverse F. proliferatum isolates. In silico analysis led to the identification of 12,980 genes common to all isolates and up to 134 genes potentially unique to an isolate. Using these resources, FUM gene cluster (~45.3 Kb) was identified for the first time in F. proliferatum. Order and orientation of the 16 FUM genes and the complete flanking genes (MSF1 and ZCB1 at 5’; ANK1 and GAT1 at 3’) have been determined. This study has provided new insights into the genetic and biological diversity of F. proliferatum and also developed new genetic and genomic resources, which will serve as a solid platform for further research particularly to understand the regulation of fumonisins production in the laboratory and in the field.

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Amoah, Bernasko Kwasi. „Pathogenicity and genetic studies of Fusarium moniliforme Sheldon“. Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337831.

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4

Lees, Alison Kathryn. „Diagnosis and control of foot rot pathogens of wheat“. Thesis, Open University, 1995. http://oro.open.ac.uk/57549/.

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Foot rot disease of wheat is caused by the pathogens Fusarium cuImorum, F.avenaceum and Microdochium nivale. Symptoms of foot rot are a general browning of the stem base and leaf sheath. There is a discrepancy between the ability of fungicides to control these pathogens in vivo and in vitro, and no relationship between disease symptom severity and yield loss has been established in wheat. The identification of the causal agents of foot rot disease is not possible from examination of disease symptoms alone. This work showed that the azole fungicides flusilazole and prochloraz inhibited the germination of conidia and mycelial growth of F. culmonon, F. avenaceum and M. nivale in vitro to a varying extent. However, no consistent control of these pathogens in wheat was observed in the field using the same fungicides. Further studies employing a semicontrolled outdoor experiment showed a relationship between density and timing of inoculum application, disease symptom severity and yield loss in wheat artificially inoculated with F. culmorum and M. nivale. Molecular marker systems were used to address the problem of pathogen detection and identification. A Random Amplified Polymorphic DNA (RAPD) assay was developed to differentiate F.culmorum, F.avenaceum and two types of M.nivale (M.nivale var.nivale and M. nivale var .majus) in vitro. Selected RAPD products were cloned and sequenced and species specific primers constructed from this sequence infonnation. These primers were used in the polymerase chain reaction (peR) and were shown to detect the pathogens in host tissue. This technique was adapted by addition of a competitor fragment to the peR reaction resulting in a quantifiable competitive peR assay. Using this method the fungal biomass of each pathogen present in the host tissue could be estimated. The development of these techniques for the identification, detection and quantification of F. cuimorum, F.avenaceum, M.nivale var.nivale and M.nivale var.majus in plant tissue will allow more extensive studies of the epidemiology of these species, the competition between species and the effect of fungicides on these pathogens can be carried out.

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Odom, Jennifer Lorraine. „Evaluation of Field Pea Varieties for Resistance to Fusarium Root Rot Pathogens“. Thesis, North Dakota State University, 2017. https://hdl.handle.net/10365/28500.

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Fusarium root rot is one of the most important diseases of pulse crops, with numerous Fusarium spp. comprising the disease complex. Fusarium solani and F. avenaceum have been reported to be major pathogens in the pea root rot complex, and all commonly grown varieties are susceptible. Greenhouse methods to evaluate peas for resistance to Fusarium root rot resulted in inconsistent disease severity across varieties. In 2015, F. avenaceum infested field plots were more heavily damaged based on emergence and yield than F. solani infested plots, and opposite trends were observed in 2016. Differences in root rot severity between years could be due to F. solani infestation causing more damage under warmer temperatures, while plots infested with F. avenaceum caused more damage under cooler temperatures. These results highlight the difficulties observed when screening for soil-borne pathogens, and the increased difficulties when a pathogen complex and changing environmental conditions are involved.

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Keyser, Zanephyn. „Parameters affecting the production of fumonisin B1 by fusarium verticillioides in culture“. Thesis, University of the Western Cape, 2001. http://hdl.handle.net/11394/4591.

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>Magister Scientiae - MSc
Fi1sarium verticillioides is a very important mycotoxin-produeing fungus associated with maize. Fverticillioides produces a group of mycotoxins known as fumonisins under suitable environmental conditions. A series of studies was designed to provide information regarding some of the factors associated with the production offumonisin B1 (FB1) in maize patties and MYRO liquid medium. Our investigation together with previous studies have detailed the important influence of several factors on the production of fumonisins by F verticillioides strains. To understand why these strains are able to produce these toxins, an investigation into the complex interaction that occurs between biotic and abiotic parameters and their impact on fumonisin production was necessary. The results reflect the interacting factors and the intraspecific differences between strains, which may also be present in field conditions. The parameters that were varied under a predetermined set of culture conditions, included initial moisture content of maize patty cultures, temperature, initial pH and the addition of the fumonisin precursors, L-alanine and L-methionineto the cultures. Investigations into the three-way interactions of initial maize patty moisture content (30 ml water to 30g of maize), L-methionine (0.3 %) and temperature (25°C), resulted in the highest yield ofFB1 (5777.26 μgig) produced by MRC 4316. In contrast, MRC 826 was negatively affected, producing lower levels ofFB1 (3492.24 μg/g), compared to MRC 4316 at an initial moisture content (20 ml water to 30 g maize), L-methionine (0.3 %) and 25 °C. An American strain of F verticillioides MRC 7424 (= NRRL 13616), produced the highest levels of FB, (116 μg/ml), while the South African isolates, MRC 4316 and MRC 826, produced lower FB1 levels (93 and 62 μg/ml, respectively) in MYRO liquid medium. In general, FB1 production in maize patty cultures far exceeded levels obtained in liquid shake cultures. It appears that not only the ability of a particular strain of F. verticillioides, but the interaction of a variety of physiological and nutritional factors and the culture medium, are important in the production of FB,. Thus, variation of a single factor such as temperature under field conditions due to seasonal change, may therefore have a major effect on fomonisin production. A chain reaction may occur when changes in moisture, pH, etc. take place, which may influence fumonisin production further. Lyophilisation of fungal cultures proves to be an excellent method to preserve a wide range of fungi over long periods of time. It is, however, necessary to determine the viability of conidia stored in lyophilised vials at 4 ° Con a regular basis. At present, plate count methods remain the most valid technique for the detection of the viability of lyophilised conidia. Membrane-permeant nucleic acid-binding dyes (FUN-I) are viability stains that are relatively new flourescent probes for assessing the viability of metabolically active yeast cells. The purpose of this study was to microscopically determine the viability oflyophilised conidia of Fusarium and A lternaria species, using the yeast, Saccharomyces cerevisiae, as a control. FUN-1 viability stain was compared to two other staining methods, i.e. ethidium bromide (EB) and methylene blue (MB) and the viability of the conidia was compared to colony-forming units (CFU) on solid media as a control. For the purpose of determining or screening for percentage viability in a specific inoculum, results indicate that EB can be used in the case of lyophilised conidia, and MB in the case of freshly harvested conidia. Although FUN-I are recommended as a good way to determine the cell viability of a fungus, it needs relatively complicated procedures and has a time limit in which the stain can be used. The result of this study emphasize that the use of dyes to determine viability of lyophilised conidia require a critical definition of protocols for a specific fungal species, and that a good correlation with CFU needs to be demonstrated. The findings of this study could find useful applications in various studies on living and dead conidial populations. The diverse toxicological effects of fumonisins m animals and plants raised the possibility that fumonisins may also inhibit the growth of filamentous fungi. This study investigated the antifungal activity of FB1 to some h1sariu111 and other fungal species. The sensitivity of these fungi was tested by an agar-diffusion method on PDA plates. FB1 inhibited the myceliaJ growth of five of the nine fungi tested. The FB1-producing Fusarium species isolated from maize, i.e. F verticil/ioides, F glohosum and F proliferatum were resistant to FB1 even though a small inhibition zone at the highest FB1 concentration of 40mM was noted in the case of F. proliferatum. However, amongst two non-producing Fusarium spp. also isolated from maize, one (F subglutinans) was resistant and one (F graminearum) was sensitive. The most sensitive fungi tested were non-producing species not isolated from maize, i.e. A lternaria alternata, Botrytis cinerea and Penicillium expansum. The minimum inhibitory concentration ofFB1 ranged between 0.25-0.SmM for A. alternata, 1-SmM for P. expansum and B. cinerea and 5-1 OmM for F. graminearum, while the other fungi tested showed no sensitivity to FB1. This is the first report on the antifungal activity ofFB1 to filamentous fungi. Another study investigated the effect of FB1 on the germination of freshly harvested conidia of Fusarium and some other fungal species. The FB1 -producing F'usarium species isolated from maize, i. e. F vertici llioides, F. globosum and F. prolifer alum showed a decrease in germ tube length with an increase in FB1 concentrations. This indicated that these fungi can tolerate their own toxic metabolite to a ce11ain extent. However, amongst the two non-fumonisin producing Fi1sarium spp. examined, i.e. F. subglutinans and F. graminearum, isolated from maize, F. subglutinans was induced to genninate faster in the presence ofFB1 but soon developed stunted germ tubes, while F graminearum developed shorter germ tubes compared to the control cultures. The most sensitive fungi tested were species not isolated from maize, i.e. A. alternata, B. cinerea and P. expansum, which did not germinate at higher FB1 concentrations at all. Statistical analyses showed that the inhibiting effect of FB1 was highly significant (P <0.001). The conidial germination bioassay was more sensitive in the detection of the antifungal activity ofFB1 than the petri dish bioassay. The minimum inhibitory concentrations of FB1 for visible mycelial growth were closely comparable to those obtained from conidial germination. Results of these studies provide considerable information on the parameters affecting the production of FB1 and will be of great benefit in further studies focussing on fumonisin prodnction.

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Matheron, Michael E., Barry R. Tickes, Martin Porchas, Charles A. Sanchez, Louis G. Didier und Kevin P. Ford. „Evaluation of Lettuce Cultivars for Resistance to Fusarium Wilt in 2003“. College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2003. http://hdl.handle.net/10150/214947.

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In the 2001-2002 production season, Fusarium wilt was observed for the first time in six different lettuce fields in the Gila and Dome Valley production areas of Yuma County, Arizona. The disease was found in 11 additional sites during 2002-2003. Fusarium wilt presents a serious threat to the health of the lettuce industry in Arizona. The only effective means of controlling Fusarium wilt of lettuce at this time is to avoid infested fields. On the other hand, Fusarium wilt in other crops, such as tomatoes and melons, is controlled effectively by planting cultivars resistant to the pathogen. The relative resistance of lettuce cultivars grown in the Arizona desert production region is unknown; therefore, a cultivar evaluation trial was established in a field known to contain the wilt pathogen, Fusarium oxysporum f.sp. lactucae. Tested cultivars were grouped into three different planting dates: Sep 7, Oct 17 and Dec 6, 2002. A majority of the cultivars within each planting date were those that would be planted in the desert at that time. Fusarium wilt was severe in the early planting of lettuce (Sep 7), moderate in the second planting (Oct 17) and very mild in the third planting (Dec 6). Disease severity was low in some lettuce cultivars in the second planting and most cultivars in the third planting. Among the types of lettuce tested, head lettuce was usually least resistant whereas romaine was most resistant. The data presented in this report are preliminary findings, subject to confirmation in another study planned for the next lettuce production season.

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Higuita, Didier Mauricio Chavarriaga. „Biological control of Fusarium spp. and other soil-borne pathogens on tree seedlings“. Thesis, University of Aberdeen, 2003. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU602315.

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Soil borne fungi isolated from forest areas and nurseries in North east of Scotland using baiting techniques, were identified using classical taxonomy and molecular methods (PCR amplification of ITS regions; restriction digestion; sequencing of PCR products) as Fusarium lateritium, F. tricinctum, F. sambucinum, Phytophthora cinnamomi, Pythium ultimum var. ultimum and Rhizoctonia binucleate (Ceratobasidium sp.). Virulence was tested in vitro on young seedlings of Pinus sylvestris and Alnus glutinosa, and Koch's postulates fulfilled through reisolation of the pathogens and confirmation of fungal penetration into host tissues. Root growth was measured using the Winrhizo program, and dry weights recorded. Symptoms on aerial parts were assessed using a categorical scale from 0 (healthy) to 5 (damage > 76%). Fusarium spp. caused significant different (P 0.01) symptom intensity on both host plants. However, no significant difference in root growth was found between treatments and control (P 0.05). The effects of different compost treatments on disease development in seedlings of both hosts inoculated with the same fine root pathogens was tested in the glasshouse confirming the virulence of the fungal pathogens on P. sylvestris and A. glutinosa seedlings. Although mean dry weights of P. sylvestris and A. glutinosa varied between compost treatments, differences were not significantly different. Isolation, characterization and identification of bacterial isolates, Bacillus subtilis B1, fluorescent pseudomonads B4 and B5 with antagonistic action against pathogens were also carried out. These isolates along with the known bacterial antagonists Bacillus subtilis MB600, MB205 and Pseudomonas corrugata R117 were used for biological control in vitro and in planta experiments using Alnus glutinosa or Pinus sylvestris seedlings. All bacterial isolates colonized root systems of both tree species. Higher numbers of bacterial cells were observed on roots of A. glutinosa than on P. sylvestris roots. High bacterial cell numbers were observed in plants of both tree species inoculated with fluorescent pseudomonads B4 or B5. In vitro antagonism on agar plates, indicated by inhibition in fungal colony diameter growth, was recorded for F. tricinctum, F. lateritium and F. sambucinum, Pythium ultimum var. ultimum and Phythophthora cinnamomi with all bacterial isolates tested (P 0.05). Biological control of the fine root pathogens on Pinus sylvestris and Alnus glutinosa seedlings by bacteria semi in vivo in test tubes was carried out with various responses in both tree hosts. All bacterial treatments resulted in a lower sporangium germination rate for P. ultimum var. ultimum than was found in controls (P 0.05). Effect of the bacterial isolates separately on growth and disease development in Pinus sylvestris and Alnus glutinosa seedlings inoculated with the pathogens under glasshouse conditions using autoclaved compost was tested. The bacterial isolates had various effects against the pathogens, although in most cases no significant differences were observed relative to controls. Further soil-based trials were carried out in the glasshouse to achieve control of root disease development on Pinus sylvestris and Alnus glutinosa using a combination of different antagonists, based on a mixture of the bacterial isolates used previously and Trichoderma koningii (TC6-Colombia). None of the antagonistic treatments showed a clear antagonistic effect in Pinus sylvestris against the fungal infections compared to control plants inoculated with the pathogens alone. In contrast, in Alnus glutinosa plants T. koningii co-inoculation improved plant growth in several of the growth parameter measured.

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Blain, François 1964. „Phytotoxicity and pathogenicity of Fusarium roseum against red clover“. Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61848.

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10

Hurley, Brett Phillip. „Fungus gnats in forestry nurseries and their possible role as vectors of Fusarium circinatum“. Diss., University of Pretoria, 2006. http://hdl.handle.net/2263/23448.

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There are many examples of associations between insects and fungi. Where the fungi involved are pathogens, such associations may be of economic importance. Insects of no economic concern alone can also become important pests because of their association with fungal pathogens. Insects may assist in the spread of pathogens by carrying them on or in their bodies. Insects may also predispose plants to infection by creating wounds during feeding, oviposition or other behavioural activities. Knowledge of associations between insects and fungal pathogens often form a crucial component in the management strategy of these pathogens. The pitch canker fungus, Fusarium circinatum, causes severe disease symptoms on mature pines in the USA. Various insects have been implicated as vectors of this disease. In South Africa, F. circinatum is reported only to cause disease on pine seedlings, where it results in severe losses in nurseries. Various insects are present in the nursery that could possibly be associated with the spread of the fungus or the infection of its hosts. Amongst these insects, fungus gnats are the prime suspects due to their history of association with fungal pathogens in other nurseries. The presence of fungus gnats in South African pine nurseries and their possible association with F. circinatum and other pathogens has never been investigated critically. The objective of this study was to expand the base of knowledge of fungus gnats in South African pine nurseries, and to consider their possible association with F. circinatum and their population structure within and between nurseries. The literature review provides a summary of fungus gnats in the nursery environment. This includes their description, biology and association with fungal pathogens. Information from these studies is used to evaluate the possible association between fungus gnats and F. circinatum in South African pine nurseries. In nurseries around the world where fungus gnats are considered pests, various control options have been used, and these are further discussed. The first research aim of this study was to determine whether fungus gnats are present in the major pine nurseries of South Africa. Thus, in Chapter 2, surveys were undertaken in four of the major pine nurseries. All fungus gnats collected were identified to species level. Other diptera collected were identified to family level. Furthermore, all diptera collected were isolated on general and selective growing medium to examine for the presence of F. circinatum. Results from Chapter 2 showed that only one species of fungus gnats was present in the nurseries and it was present in all four of the nurseries surveyed. This raised interesting questions regarding the phylogeographic structure of these populations and the diversity within and between populations. These questions are addressed in Chapter 3 using analysis of mitochondrial COI sequence data from fungus gnats collected in the four nurseries. Of particular importance was the interpretation of these results as it pertains to the movement of fungus gnats between populations, together with their associated fungi. Using general and specific growing medium to isolate fungal pathogens from insects is not necessarily an accurate method. Pathogens may be overgrown by faster growing fungi before they are noticed, especially if they are present only in small amounts. Chapter 4 examined the use of DNA-based methods as a tool to detect fungal pathogens on fungus gnats. Fungus gnats were collected from the same four nurseries as in Chapter 2. Species-specific primers for F. circinatum and Botrytis cinerea were used to detect these fungi. Dilution series were done to examine the sensitivity of the primers. General primers were used to detect other fungi. This dissertation includes some of the first studies ever undertaken on fungus gnats in South African pine nurseries. Their association with the very virulent pitch canker fungus is also considered in some detail. It is my hope that these studies will form a foundation for future research on fungus gnats in South Africa. Copyright
Dissertation (MSc)--University of Pretoria, 2006.
Zoology and Entomology
unrestricted

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Pedrozo, Rodrigo. „Characterization of soybean seedborne Fusarium spp. in the state of Kansas, USA“. Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35737.

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Doctor of Philosophy
Department of Plant Pathology
Christopher R. Little
Fusarium spp. are among the most important pathogen groups on soybeans. However, information regarding this genus on soybean seeds in the state of Kansas remains underexplored. Therefore, the goal of this study was to characterize the identity, frequency, and pathogenicity of soybean seedborne Fusarium spp. in the state of Kansas. For the identification and frequency of seedborne Fusarium spp., culture-dependent (i.e. semi-selective medium) and -independent (i.e. DNA metabarcoding) approaches were used. Also, information regarding the pathogenicity of the most common seedborne Fusarium spp. from soybeans was assessed to better understand their role as soybean pathogens. Overall, eleven Fusarium spp. were identified in this study. Semi-selective media showed that approximately 33% of soybean seed samples were infected with Fusarium spp. Moreover, Fusarium spp. were isolated from seed sampled from 80% of the locations in Kansas. Furthermore, a low incidence of Fusarium spp. was observed within infected seed samples and averaged 2%. Nine Fusarium spp. were found in soybean seeds using the culture-dependent approach. Fusarium semitectum was the most frequent, followed by F. proliferatum and F. verticillioides. Fusarium acuminatum, F. equiseti, F. fujikuroi, F. graminearum, F. oxysporum, and F. thapsinum were found in lower frequencies among naturally infected seeds. DNA metabarcoding experiments showed that Fusarium spp. are more frequent in soybean seeds than previously known. All asymptomatic soybean seeds analyzed, using Illumina MiSeq platform, showed the presence of the genus Fusarium including two pathogenic species, F. proliferatum and F. thapsinum. Fusarium acuminatum, F. merismoides, F. solani, F. semitectum, and Fusarium sp. were also identified using the culture-independent approach. Preliminary results also showed that F. proliferatum and F. thapsinum were observed in all three major soybean seed tissues: seed coat, cotyledons, and the embryo axis. Depending on the soybean genotype, inoculum potential and aggressiveness, F. proliferatum, F. graminearum, F. fujikuroi, F. oxysporum, F. semitectum, F. thapsinum, and F. verticillioides were pathogenic to soybean and negatively affect soybean seed quality, at different levels, in controlled conditions. Moreover, F. equiseti and F. acuminatum did not cause significant damage to soybean seeds and seedlings. Understanding seedborne Fusarium spp. and their influence on soybean seed and seedling diseases is critical for the development of effective disease control strategies, especially regarding early detection of pathogenic strains in seeds (i.e., seed health testing), ensuring the crop productivity, quality, and safety.

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Eldon, Simon. „A comparative study of the resistance mechanisms of upland cotton (Gossypium hirsutum, L.) to Fusarium oxysporum f.sp. vasinfectum and Verticillium dahliae“. Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283652.

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Drakulic, Jassy. „Ecological interactions between grain aphids (Sitobion avenae) and Fusarium head blight pathogens (Fusarium graminearum & F. langsethiae) on wheat and their impact on disease“. Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/34002/.

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Fusarium head blight pathogens contribute to ear disease in cereals globally, causing yield losses, decreased grain quality, and mycotoxin accumulation in infected grain. Wheat is susceptible to head blight disease after ear emergence, during which time ears can also act as hosts for other biological agents, including insects. Grain aphids, Sitobion avenae, colonise ears preferentially over other tissues of wheat plants, and mutual attack of wheat by grain aphids and Fusarium pathogens is likely to occur in the field. Experiments were conducted to elucidate the nature of the interactions that occur between the plant host, aphid pests and Fusarium pathogens. When aphids had also attacked the host plant, exacerbated disease severity was observed for both Fusarium graminearum and F. langsethiae. Of particular interest was the finding of an increase in mycotoxin accumulation in infected grain when there was aphid herbivory of host plants. Transmission of either species by aphids was not consistently observed, although the apparent compatibility of F. langsethiae with aphid vectors was greater than for F. graminearum. F. langsethiae was transmitted by aphids when moved manually from infected host ears to susceptible healthy ears, but transmission by natural movement of both winged and wingless aphids failed to produce disease in new hosts. In contrast, deoxynivalenol-producing F. graminearum induced the production of volatile host chemicals that repelled aphids, and population dynamics of aphids that colonised wheat ears infected with F. graminearum were impacted negatively, as observed by increased mortality and decreased fecundity of aphids from diseased hosts. The role of mycotoxins in the production of host volatiles was assessed by comparing F. graminearum isolates of different chemotypes, including mycotoxin deficient mutants. In contrast to hosts infected with DON-producing F. graminearum, which produced VOCs that repelled aphids, hosts infected with a nivalenol (NIV)-producing F. graminearum isolate produced VOCs that were attractive to aphids. This response was shown to be due to the mycotoxin production of the pathogen, as a transgenic line of the same isolate deficient impaired in trichothecene production produced no such effect. The importance of timing and location of aphid herbivory relative to the infection site on the development and spread of disease was examined. It was observed that the longer the time of aphid colonisation on hosts prior to the arrival of fungal inoculum, the more severe the consequences of disease for host plants in terms of fungal biomass and visual disease severity. Aphid herbivory on host ears led to a greater increase in disease severity and spread than infestation of leaves. Systemically treated plants also became more vulnerable to elevated pathogen colonisation; however local effects were more influential on disease outcome. The current research findings show the value of considering interactions between plant pathogens and insects. These are usually studied separately but occur together in nature and in this case the insect had a major impact on disease development. This opens questions about how aphids improve host suitability which could be answered by transcriptomic approaches. The study has important practical implications because it suggests that by incorporating traits for resistance to aphids, breeding for FHB resistance could be improved in wheat. Furthermore, control of aphid populations prior to and during heading could reduce the risk of mycotoxin contamination of wheat crops.

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Al-Maqtoofi, Marwan Yaseen Abdulmajeed. „Investigating host and environmental influences of Fusarium solani using a novel monoclonal antibody“. Thesis, University of Exeter, 2016. http://hdl.handle.net/10871/23409.

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Human fungal infections among severely immunocompromised individuals have increased dramatically over the last 30 years and that coincidence with an expanding patient numbers of bone marrow and solid organ transplantation and those receiving aggressive cytotoxic chemotherapy for neoplastic diseases or immunosuppressive drugs. In recent years, many of opportunistic fungi have emerged as serious human pathogens and causing life-threatening infections of humans such as Fusarium species. Due to lack of a highly accurate diagnostic test for tracking the pathogenic Fusarium species, fusariosis is frequently misdiagnosed as aspergillosis. Delays in identification and differentiation of Fusarium spp. from other causative agents of hyalohyphomycetes associated with high morbidity and mortality rate among immunocompromised patients. This research aimed to develop a highly specific monoclonal antibody (mAb) using hybridoma technology to produce a highly genus-specific murine mAb ED7 that could be used for tracking and early detecting circulating Fusarium species antigens from other opportunistic pathogens. At present, a very little is known about the pathogenicity and interaction of human pathogenic F. solani and cells of the innate immune system like alveolar macrophages (AMØ), the residential innate immune cells of alveoli. For this reason, F. solani was genetically transformed with GFP gene and a model of immunoassay was developed to investigate the interactions of F. solani with AMØ that would allow studying the fungal pathogenicity, visualising and quantification of the pathogen during the process of macrophage phagocytosis. In addition, this model can be used to evaluate the effect of a mAb on fungal uptake by AMØ. Habitates providing direct human exposure to infectious propargules are largely unknown, but there is growing evidence that plumbing systems are sources of human pathogenic strains in the F. solani and F. oxysporum species complexes, the most common groups infecting humans. Using mAb ED7 specific to the Fusarium species, this work demonstrates how the mAb can be used as a powerful immunodiagnostic tool for accurately tracking the Fusarium species antigens in sink drain biofilms and water system samples containing mixed populations of human opportunistic filamentous and yeasts pathogenic fungi across a University campus and a tertiary care hospital. Specificity of the ELISA was confirmed by sequencing of the internally transcribed spacer 1 (ITS1)-5.8S-ITS2 rRNA-encoding regions of culturable yeasts and moulds that were recovered using mycological culture, while translation elongation factor (TEF)-1 analysis of Fusarium isolates included FSSC 1-a, FOSC 33 and FDSC ET-gr, the most common clinical pathotypes in each group. The mAb ED7 is, therefore, suitable to be carried forward for use in diagnostic assays, such as the lateral flow device.

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Filgueira, Pimentel Mirian. „EVALUATION AND FUNCTIONAL CHARACTERIZATION OF BIOCONTROL AGENTS TARGETING SELECT SOILBORNE PATHOGENS OF SOYBEAN“. OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1886.

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Soybean crops are vulnerable to a wide range of pathogens that reduce yield and cause extensive losses worldwide. In the United States, the soilborne pathogens Pythium spp., causing soybean damping-off, and Fusarium virguliforme, causing sudden death syndrome (SDS) of soybean, have been among the top diseases that most reduced soybean yields. This study demonstrated that biological control using native fungal antagonists could be a powerful tool to integrate with current management strategies for more efficient control of Pythium damping-off and SDS in soybean. Trichoderma spp. and Clonostachys rosea demonstrated the ability to mycoparasitize and antagonize the pathogens using different mechanisms and exhibited a protective effect on soybean in field conditions. The development of an efficient biological control program for disease management relies on a deep understanding of the BCA-pathogen interaction’s biology. This research also uncovered the molecular mechanisms involved in the F. virguliforme-T. afroharzianum interaction by using a dual RNAseq approach. Significant changes in both fungal organisms’ transcriptomes were discovered at different stages in their interaction. The results provided here can contribute to the future implementation of effective biological control programs for soybean. The benefits may also extend to other crops.

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Coomber, Scott William. „Plants, pathogens and mycorrhiza : a study of the interaction between Vulpia ciliata, Glomus sp. and Fusarium oxysporum“. Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323242.

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Moya, Ernesto Antonio. „Distribution and interaction of Fusarium crown rot and common root rot pathogens of wheat in Montana and development of an integrated management program for Fusarium crown rot“. Thesis, Montana State University, 2010. http://etd.lib.montana.edu/etd/2010/moya/MoyaE0810.pdf.

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This thesis had three objectives: i) Determining distribution of FCR and common root rot (CRR) of wheat in Montana; ii) Determining population dynamics between F. pseudograminearum and Bipolaris sorokiniana at different wheat development stages, and iii) Development of an integrated disease management program for Fusarium crown rot (FCR) using biological and fungicide seed treatments, cultivar resistance, and induced systemic resistance (SAR). Surveys of 91 fields over two years using qPCR identified FCR in 57% and CRR in 93% of the fields surveyed. Bipolaris sorokiniana, F. culmorum and F. pseudograminearum were isolated from 15, 13 and 8% of tillers respectively. FCR distribution was highly clustered while CRR was uniformly distributed with soil type, elevation and growing degree days influencing distribution. Data from intensively sampled fields estimated yield losses caused by FCR and CRR at 3.2 to 34.9% with losses influenced by pathogen population. This study is the first time qPCR was used to survey the distribution of FCR and CRR and to study the interaction of the respective pathogens. The effect of F. pseudograminearum and B. sorokiniana inoculum applied singly or in combination at three rates showed high and low rates of F. pseudograminearum inoculum reduced Bipolaris populations, while B. sorokiniana inoculations did not affect Fusarium populations in stems. Populations of both pathogens increased from heading until harvest with Fusarium colonizing stems earlier than Bipolaris. Mixed inoculations increased incidence of infection and co-infection relative to that observed in production fields. Both fungi alone or combined reduced the seedling counts. Grain yield was inversely correlated with Fusarium populations. Difenoconazole-mefenoxam seed treatment reduced FCR severity between 29.3-50% and fungal and bacterial seed treatments were ineffective. The cv. Volt was identified as partially resistant and had the highest levels of chitinase and beta-1, 3-glucanase activity of cultivars evaluated. Induction of SAR by Bacillus mycoides isolate BmJ or acibenzolar Smethyl significantly reduced the severity of FCR compared to water controls. Integration of cultivar resistance plus fungicide seed treatment or SAR induction provided equal control in greenhouse and irrigated trials. In a dryland field trial, integration of all management tools reduced FCR more than individual tools.

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Paré, Monique. „Effects of covering composted vegetable wastes on quality of compost, quality and composition of leachate, and survival of plant pathogens“. Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20835.

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Composting trials were undertaken to study the feasibility of using crucifer or carrot residues with straw or sawdust for composting. Compost temperature and moisture were monitored regularly, and compost samples were analyzed for physico-chemical characteristics at the beginning in the fall, before turning in spring, and at the end of each composting cycle. A geotextile cover was tested. Compost leachate volumes were measured throughout the two composting cycles. In addition, the leachate was submitted to phytotoxicity tests and physico-chemical analyses. Selected phytopathogens were introduced in the compost in order to assess their potential for survival during the composting process. Three pathogens having resistant survival structures were included: Plasmodiophora brassicae, Fusarium oxysporum f.sp. cucumerinum , and Sclerotinia sclerotiorum. Greenhouse growth trials were performed with compost-enriched media and a commercial mix. (Abstract shortened by UMI.)

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Ghazala, Al-Sadek Mohammed Salem. „Proteomic responses of uninfected tissues of pea plants infected by root-knot nematode, Fusarium and downy mildew pathogens“. Thesis, University of the West of England, Bristol, 2012. http://eprints.uwe.ac.uk/18313/.

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Peas suffer from several diseases, and there is a need for accurate, rapid in-field diagnosis. This study used proteomics to investigate the response of pea plants to infection by the root knot nematode Meloidogyne hapla, the root rot fungus Fusarium solani and the downy mildew oomycete Peronospora viciae, and to identify potential biomarkers for diagnostic kits. A key step was to develop suitable protein extraction methods. For roots, the Amey method (Chuisseu Wandji et al., 2007), was chosen as the best method. The protein content of roots from plants with shoot infections by P. viciae was less than from non-infected plants. Specific proteins that had decreased in abundance were (1->3)-beta-glucanase, alcohol dehydrogenase 1, isoflavone reductase, malate dehydrogenase, mitochondrial ATP synthase subunit alpha, eukaryotic translation inhibition factor, and superoxide dismutase. No proteins increased in abundance in the roots of infected plants. For extraction of proteins from leaves, the Giavalisco method (Giavalisco et al., 2003) was best. The amount of protein in pea leaves decreased by age, and also following root infection by F. solani and M. hapla at six weeks post-inoculation. F. solani caused a decrease in abundance of isocitrate dehydrogenase, glycerate dehydrogenase, carbonic anhydrase, oxygen evolving enhancer protein 2 (OEE2), phosphoglycerate kinase, chloroplastic and one unknown protein. Some leaf proteins increased in abundance, and included heat shock-related proteins (HSP70) and two unknown proteins. Proteins that decreased in leaves following root infection by M. hapla six week post-inoculation were RuBisCo large subunit, fructose bisphosphate aldolase 2, carbonic anhydrase, OEE1, OEE2, OEE3, RuBisCo small subunit and a 28KDa ribonucleoprotein. Some proteins increased in abundance, such as HSP70, fructose bisphosphate aldolase 1 and trypsin. In contrast to the decrease in protein observed at six weeks post-inoculation, the amount of protein increased in leaves three weeks after inoculation of roots with M. hapla. Root infection by both M. hapla and F. solani caused a reduction in leaf area, and also a reduction in fresh and dry weight of the shoot and root systems. The use of digital imaging and visible and infra-red light to study the changes in leaves was explored in this study. A clear difference was visible between leaves from healthy plants and between those from M. hapla and F. solani infected plants when imaged using a normal digital camera. In contrast, no clear differences were noticed between leaves of healthy, M. hapla and F. solani infected plants when using an infra-red camera with 850 nm wavelength light. This study indicates that specific proteins are altered in abundance in leaves following root infection, and provides the basis for future studies to develop rapid diagnostic tests.

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Moročko, Inga. „Characterization of the strawberry pathogen Gnomonia fragariae, and biocontrol possibilities /“. Uppsala : Dept. of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/200671.pdf.

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Carter, Mel. „Investigating novel approaches for the integrated control of the soilborne strawberry pathogens Macrophomina phaseolina and Fusarium oxysporum f. sp. fragariae“. DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1628.

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Macrophomina phaseolina (Mp) and Fusarium oxysporum f. sp. fragariae (Fof) are emerging soilborne pathogens causing crown rot and Fusarium wilt, respectively, in commercial strawberry production in California. Fungicides representing eight active ingredients from four different mode of action groups (FRAC groups 1, 3, 7 and 12) were evaluated for their efficacy against each pathogen in vitro and each disease in planta. Fungicide active ingredients were evaluated for their ability to inhibit mycelial growth of both pathogens in vitro. Half-strength potato dextrose agar was amended with six different concentrations (0.01, 0.1, 1.0, 5.0, 10, 50 µg a.i./ml) of seven fungicides in FRAC groups 3, 7 and 12. Concentrations that inhibited fungal growth by 75% (EC75) compared to unamended media were determined for two different isolates each of Mp and Fof and were used to determine fungicide rates for subsequent in planta studies. Tebuconazole strongly inhibited the mycelial growth of both pathogens (average EC75 for Mp was 2.4 ppm; average EC75 for Fof was 7.48 ppm), as did metconazole (average EC75 for Mp was2.53 ppm; average EC75 for Fof was 1.28 ppm). Fludioxonil strongly inhibited mycelial growth of Mp, but had no impact on the growth of Fof. Penthiopyrad, fluopyram, flutriafol, and flutolanil were less effective at inhibiting fungal growth of either fungus. Greenhouse in planta studies evaluated twenty-four fungicide treatments (eight fungicides at low, med and high rates) that were drench applied to infested potting media two days prior to planting of pathogen susceptible strawberry cultivars (San Andreas for Mp and Monterey for Fof) and again at day 21. Controls were a non-inoculated and an inoculated water-drench treatment. Buried inoculum was recovered at days 2 and 23 and plated on selective media for colony forming unit (CFU) quantification. Plant disease assessments were made each week for 11 weeks. An analysis of variance (ANOVA) of CFUs revealed no significant differences (p > 0.05) among treatments and when compared to the non-treated control for both Mp and Fof, but showed significant decreases (p < 0.05) in CFUs between weeks 1 and 3 for both Mp and Fof. An ANOVA for disease assessments in the form of area under the disease progress curve (AUDPC) showed significant decreases of disease severity in treatments with penthiopyrad only (low, medium and high rates) (p < 0.05). There were no significant differences (p > 0.05) in AUDPC among treatments and when compared to the non-inoculated and no-fungicide controls for Fof. The data indicates that these fungicides used alone are not effective against these pathogens in planta. A strawberry plant extract (germination stimulant) was assessed for its ability to stimulate germination of Mp microsclerotia in vitro and in planta. The germination stimulant was applied as a drench at six different concentrations (0, 10, 100, 1,000, 10,000 and 30,000 ppm) to soil containing filter disk packets of microsclerotia of Mp at day 0 and 14. Filter disk packets were retrieved three days after the drench and microsclerotia were observed microscopically for germination. Results showed that the number of germinating microsclerotia was significantly higher after the application of the germination stimulant compared to non-drench and 0 ppm controls (p < 0.001). An integrated container trial was also conducted using the germination stimulant at 10,000 ppm applied three days prior to a fungicide drench with tebuconazole or thiophanate-methyl to determine the effect of fungicides on the germinated microscleotia. The use of the germination stimulant with label rates of the fungicides lowered the number of germinated intact microsclerotia significantly (p < 0.001) especially after two drench applications. The use of the germination stimulant with fungicides could be investigated further as one method for controlling soilborne diseases of strawberry.

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Costa, Juliana Leles. „Estudos histológicos e moleculares da interação Musa spp. x Fusarium oxysporum f. sp. cubense“. Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/11/11137/tde-29052013-170512/.

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A doença da bananeira \'mal-do-Panamá\', causada pelo fungo Fusarium oxysporum f. sp. cubense (Foc) é uma das doenças mais destrutivas da bananeira e é considerada uma das seis doenças economicamente mais importante da história da humanidade. Algumas cultivares resistentes, como a \'BRS Platina\', foram lançadas pela Embrapa, porém para a sustentabilidade da resistência é necessário entender os mecanismos moleculares envolvidos na resposta de resistência e defesa. O objetivo deste estudo foi caracterizar o processo de infecção pelo Foc raça 1 em três cultivares contrastantes para a resistência e analisar o padrão transcricional no início da interação. A análise histopatológica indicou que o Foc raça 1 penetra pela raízes laterais e principal, colonizando os espaços inter e intracelular do córtex nas três cultivares. Foram visualizadas, hifas \'globosas\' na cultivar suscetível \'Maçã\' com a formação de estruturas de resistência, como clamidósporos. Na cultivar resistente \'BRS Platina\', foi observado por microscopia óptica no período inicial da interação (24 horas após inoculação) a indução de respostas de defesa da planta, como formação de zona de cicatrização, e aos 15 dias após inoculação, formação de tilose, presença de cristais de oxalato de cálcio e deposição de calose. Foi utilizada a tecnologia Illumina para sequenciamento massal de RNA e abordagens de bioinformática para identificar genes diferencialmente expressos (DE) relacionados com a resposta de defesa de bananeira em interações compatíveis e incompatíveis. O sequenciamento paired-end gerou um total de 113.632.486 fragmentos (reads) com alta qualidade. Do total de reads alinhados no genoma referência (\'DH-Pahang\'), 55.555.480 alinharam-se com genes conhecidos e anotados no genoma referência, sendo utilizados para a análise DE inoculado x não inoculado, permitindo detectar 2.307 genes para as três cultivares. Os genes anotados de cada cultivar foram comparados, sendo identificados quatro genes comuns para as três cultivares, dez compartilhados entre \'Maçã\' e \'Prata-anã\', 21 compartilhados entre \'BRS Platina\' e \'Maçã\', 114 compartilhados entre \'BRS Platina\' e \'Prata-anã\', além de 75 serem exclusivos de \'Maçã\', 599 de \'BRS Platina\' e 1484 de \'Prata-anã\'. O mecanismo de resistência/defesa ao Foc em \'BRS Platina\', ocorre em nível de percepção precoce na presença do patógeno desencadeando resposta de defesa inexistente em \'Maçã\', e com cinética distinta da cultivar com resposta intermediária (\'Prata-anã\'). Dessa forma, os resultados permitiram propor um modelo da resposta de defesa/resistência ao Foc raça 1 em bananeira, baseando-se no nível de indução de genes que codificam para proteínas de reconhecimento do patógeno (receptor like kinase), fatores de transcrição (WRKY e MYB); reforço e síntese de parede celular, degradação da parede celular do fungo (quitinase e glucanases), heat shocks, enzimas antioxidantes e na resposta visualizada pela histologia na cultivar \'BRS Platina\'. Sendo assim, este trabalho fornece novas perspectivas para estudos de análise funcional, identificação e anotação de novos genes relacionados a resposta de defesa e resistência ao Foc raça 1.
The banana Panama disease, caused by fungus Fusarium oxysporum f. sp. cubense (Foc), is one of the most destructive disease of the industry, and it is considered one of the six most economically important of all times. A few cultivars, such as \'BRS Platina\', were released, but it is still necessary to understand molecular mechanisms involved in defense response and resistance. The objective of this study was to characterize the infection process by Foc in three banana cultivars contrasting for resistance to Foc and to analyze the transcriptional profile at the beginning of interaction. In this way, Foc race 1 penetrated the main and lateral roots, colonizing inter- and intracellular spaces of the root cortex in the three cultivars. Hyphae were globose in the susceptible cultivar \'Maçã\' with the formation of resilience structure, such as chlamydospores. In the resistant cultivar \'BRS Platina\', during the initial period of interaction (24 hours after inoculation), induced of plant defense responses, such as a healing zone, tylosis formation, presence of calcium oxalate and callose deposition. The Illumina technology were applied to sequence RNA, followed by bioinformatic tools to identify genes differentially expressed (DE) related to resistance and defense response in the compatible and incompatible interactions. Pair-end sequencing generated a total of 113,632,486 reads with high quality. From the total of aligned reads to the banana reference genome (\'DH-Pahang\'), 55,555,480 aligned with gene models annotated in the reference genome. The aligned contigs were analysed for DE, comparing inoculated x non-inoculated, enabling the detection of 2307 genes for the three cultivars. Each annotated gene from each cultivar was compared: four common genes to the three cultiars; 10 genes were shared between \'Maçã\' and \'Prata-anã\'; 21 shared between \'BRS Platina\' and \'Maçã\'; 114 shared between \'BRS Platina\' and \'Prata-anã\', plus 75 exclusive to \'Maçã\'; 599 exclusive to \'BRS Platina\' and 1,484 to \'Prata-anã\'. The mechanism of resistance/defense in \'BRS Platina\', level of perception occurs early in the presence of the pathogen defense response triggering nonexistent in \'Maçã\' and with kinetics distinct cultivar with intermediate response (\'Prata-anã\'). Thus, the results have provided a model of defense response/resistance to Foc race 1 in banana, based on the level of gene induction that encode recognition proteins (Receptor-like Kinase, RLK), transcription factors (WRKY and MYB), cell wall synthesis and reinforcement, degradation of fungal cell wall (chitinases and glucanases), heat shocks , proteins;anto-oxidative enzymes and visualized by histologcal in response cultivar \'BRS Platina\'. The present work offer new perspectives to functional analyses, identification and annotation of new genes related to resistance and defense response to Foc race 1.

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Southwood, Michael J. „Evolution and detection of Fusarium oxysporum f. sp. cepae in onion in South Africa“. Thesis, Stellenbosch : Stellenbosch University, 2010. http://hdl.handle.net/10019.1/4499.

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Thesis (PhDAgric (Plant Pathology))--Stellenbosch University, 2010.
ENGLISH ABSTRACT: In the Western Cape onion industry in South Africa, Fusarium oxysporum Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep) has been identified as the leading cause of harvest and storage losses. This pathogen is of world-wide importance and causes Fusarium basal rot of onions (Allium cepa), affecting all onion growth stages. No information is available on the evolution, genetic diversity, molecular detection and inoculum sources of the South African Focep population. Similar to what is the case for South Africa, limited information is available on Focep in other regions of the world. World-wide, four vegetative compatibility groups (VCGs) and two single-member VCGs (SMVs) have been identified among two Japanese and 19 Colorado (USA) isolates. This polyphyletic origin of Focep suggested by VCG analyses was confirmed through molecular analyses of isolates from a few countries. Only the mating type (MAT)1-1 idiomorph has been reported for Focep isolates from Welsh onion (Allium fistulosum). The development of sustainable management strategies of Focep is dependent on knowledge of (i) the genetic diversity and evolution of Focep, (ii) whether high throughput molecular methods can be developed for identifying the most virulent and widespread Focep genotypes and (iii) the role of seedlings and seeds as primary inoculum sources, and the Focep genotypes associated with these growth stages. Therefore, the three main aims of the current study were to investigate the aforementioned three aspects. In the first aim of the study, the genetic diversity and evolution of Focep was investigated using a collection of 79 F. oxysporum isolates from South Africa (27 Focep and 33 non-pathogenic isolates) and Colorado (19 Focep isolates). VCG analyses revealed the presence of six VCGs, four among the Colorado Focep isolates (VCGs 0421, 0422, 0423 and 0424) and two among the South African bulb-associated isolates (VCGs 0425 and 0426). VCG 0421 and VCG 0425 were the two main VCGs in Colorado and South Africa, respectively. Four SMVs and one heterokaryon selfincompatible (HSI) isolate were also identified. The polyphyletic nature of Focep in South Africa and Colorado was shown through a combined translation elongation factor 1α (EF-1α) and mitochondrial small-subunit (mtSSU) phylogeny. The phylogeny divided the Focep isolates into two main clades, of which one contained the two main VCGs (0421 and 0425), SMVs and non-pathogenic isolates. The second, ancestral clade contained the HSI isolate, VCGs 0422, 0423 and 0424, and non-pathogenic isolates. Unlike the clade containing the two main VCGs, which were highly virulent toward onion bulbs, the ancestral clade contained isolates that were mostly moderately virulent. The incongruence of the EF-1α and mtSSU datasets with an intergenic spacer (IGS) region data set, and the presence of both MAT idiomorphs within the same isolate for some isolates, suggested possible exchange of genetic material between isolates. The second aim of the study was to develop molecular methods for identifying the two main Focep VCGs (0425 and 0421), using DNA fingerprinting methods and sequence-characterized amplified region (SCAR) markers. These techniques were first developed using the F. oxysporum isolates from the first aim, and were then used to investigate the prevalence of VCG 0425 among 88 uncharacterized F. oxysporum isolates from onion bulbs in South Africa. Two random amplified polymorphic DNA primers provided two diagnostic amplicons for VCG 0425, but attempts to develop SCAR markers from these amplicons were unsuccessful. In contrast, an interretrotransposon amplified polymorphism (IRAP) fingerprinting method enabled the developed of a multiplex IR-SCAR polymerase chain reaction method that detected the VCG 0421, 0425 and SMV 4 isolates as a group. Fingerprinting and SCAR marker testing of the 88 uncharacterized F. oxysporum isolates from South Africa (65 Focep and 23 non-pathogenic) confirmed that VCG 0425 is the main VCG in South Africa associated with mature onion bulbs, since 63 of the Focep isolates had the molecular characteristics of VCG 0425. The third aim of the study was to determine whether seed and seedling transplants are inoculum sources of Focep, and whether the same genotype (VCG 0425) that dominated on mature bulbs could be detected from these sources. Focep isolates were obtained from seven of the 13 investigated onion seed lots, as well as from onion seedling transplants that were collected from all five onion nurseries in the Western Cape. Focep seedling infection more than doubled from the 6-week growth stage to the 14-week growth stage. Seed infections by Focep were low, but the seedborne nature of Focep was confirmed by showing that a green fluorescent protein labelled Focep transformant could be transmitted from infected soil to onion seed via the onion bulbs and seedstalks. It is thus clear that commercial seed and seedlings are inoculum sources of Focep. However, the Focep genotypes on seed and seedlings are different from those in mature bulbs and were not dominated by VCG 0425. Furthermore, most (≤ 60%) of the seed and seedling isolates were moderately virulent, as compared to the mostly highly virulent isolates from mature bulbs.
AFRIKAANSE OPSOMMING: In die Wes-Kaapse uiebedryf in Suid-Afrika is Fusarium oxysporum Schlechtend.:Fr. f.sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans. (Focep) geïdentifiseer as die vernaamste oorsaak van oes- en opbergingsverliese. Hierdie patogeen is van wêreldwye belang; dit veroorsaak Fusarium-bolvrot van uie (Allium cepa) en affekteer alle plantgroeistadia. In Suid-Afrika is daar geen inligting beskikbaar oor die evolusie, genetiese diversiteit, molekulêre opsporing en inokulumbronne van die Focep-populasie nie. Soortgelyk aan wat die geval in Suid-Afrika is, is daar beperkte inligting beskikbaar oor Focep in ander wêrelddele. Wêreldwyd is daar vier vegetatiewe versoenbaarheidsgroepe (VVGe) en twee enkellid VVGe (ELVe) geïdentifiseer onder twee Japannese en 19 Colorado (VSA) isolate. Hierdie veelvuldige oorsprong van Focep wat deur VVG-analise voorgestel was, is deur die molekulêre analises van isolate uit ’n paar ander lande bevestig. Slegs die paringstipe (PT)1-1 idiomorf is vir Focep-isolate uit Walliese-tipe uie (ook bekend as ‘lenteuie’ in Suid Africa) (Allium fistulosum) berig. Die ontwikkeling van volhoubare bestuurstrategieë vir Focep steun op kennis van (i) die genetiese diversiteit en evolusie van Focep, (ii) of hoë-deurset molekulêre metodes ontwikkel kan word vir die identifisering van die mees virulente en wydverspreide Focep-genotipes en (iii) die rol van saailinge en saad as primêre inokulumbronne, en die Focep-genotipes wat met hierdie groeistadia geassosieer word. Daarom was die hoof doelstellings van hierdie studie om die bogenoemde drie aspekte te bestudeer. Om die eerste doel van die studie te bereik is die genetiese diversiteit en evolusie van Focep bestudeer deur gebruik te maak van ‘n versameling van 79 F. oxysporum-isolate uit Suid-Afrika (27 Focep en 33 nie-patogeniese isolate) en uit Colorado (19 Focep-isolate). VVG-analises het die teenwoordigheid van ses VVGe aangetoon – vier onder die Colorado Focep-isolate (VVGe 0421, 0422, 0423 en 0424) en twee onder die Suid-Afrikaanse bol-geassosieerde isolate (VVGe 0425 en 0426). VVG 0421 en VVG 0425 was die twee hoof VVGe in onderskeidelik Colorado en Suid-Afrika. Vier ELVe en een meerkernige self-onversoenbare (MSO) isolaat is ook geïdentifiseer. Die veelvuldige oorsprong van Focep in Suid-Afrika en Colorado is ook aangetoon deur ‘n gekombineerde translasie verlengings faktor 1α (VF-1α) en mitokondriale klein-subeenheid (mtKSE) filogenie. Dié filogenie het die Focepisolate in twee groepe verdeel, waarvan die een groep die twee hoof VVGe (0421 en 0425), ELVe en nie-patogeniese isolate bevat het. Die tweede, basal groepering het die MSO-isolaat, VVGe 0422, 0423 en 0424, en nie-patogeniese isolate bevat. In teenstelling met die eersgenoemde groepering wat hoogs virulente isolate van uiebolle bevat het, het die basale groepering isolate bevat wat meestal matig virulent was. Die inkongruensie van die VF-1α en mtKSE-datastelle met ‘n intergeen-gespasieerde (IGS) area datastel – asook die teenwoordigheid van beide PT-idiomorwe binne dieselfde isolaat by sommige isolate – het op ’n moontlike uitruiling van genetiese materiaal tussen isolate gedui. Die tweede doel van die studie was om molekulêre metodes te ontwikkel vir die identifisering van die twee hoof Focep VVGe (0425 en 0421) deur gebruik te maak van DNA-vingerafdrukke en nukleotied-gekarakteriseerde geamplifiseerde area (NKAA) merkers. Hierdie tegnieke is ontwikkel deur van die F. oxysporum-isolate van die eerste doelstelling gebruik te maak en is daarna gebruik om die frekwensie van VVG 0425 onder 88 ongekarakteriseerde F. oxysporum-isolate van uiebolle in Suid-Afrika te ondersoek. Twee gerandomiseerde geamplifiseerde polimorfiese DNS (RAPD) merkers het twee diagnostiese nukleotiedbasis-areas vir VVG 0425 gelewer, maar pogings om NKAA-merkers uit hierdie geamplifiseerde nukleotiedbasis-areas te onwikkel was onsuksesvol. In teenstelling hiermee het ‘n inter-retrotransposon geamplifiseerde polimorfisme (IRAP) vingerafdrukmetode die ontwikkeling van ‘n multipleks IR-NKAA polimerase kettingreaksiemetode moontlik gemaak wat die VVG 0421-, VVG 0425- en ELV 4-isolate as ’n groep aangedui het. Vingerafdruktoetsing en NKAA-merkertoetsing van die 88 ongekaraktariseerde F. oxysporum isolate van Suid-Afrika (65 Focep en 23 nie-patogenies) het bevestig dat VVG 0425 die hoof VVG in Suid-Afrika is wat met volwasse bolle geassosieer word, aangesien 63 van die Focep-isolate die molekulêre eienskappe van VVG 0425 gehad het. Die derde doel van die studie was om vas te stel of saad en saailinge inokulumbronne van Focep is, en of dieselfde genotipe (VVG 0425) wat op volwasse bolle dominant is, waargeneem kon word op hierdie bronne. Focep-isolate is verkry van sewe van die 13 uiesaadlotte asook van uiesaailinge wat in al vyf uiesaailingkwekerye in die Wes-Kaap versamel is. Focep-saailinginfeksie was meer as dubbel in die 14-week groeistadium as wat dit in die 6-week stadium was. Saadinfeksies deur Focep was laag, maar die saadgedraagde aard van Focep is bevestig deur aan te toon dat ’n Focep-transformant wat met ‘n groen fluoreserende proteïen geëtiketeer is, van geïnfekteerde grond na uiesaad oorgedra kon word via die uiebolle en -saadstele. Dit is dus duidelik dat kommersiële saad en saailinge as inokulumbronne van Focep dien. Die Focep-genotipes op saad en saailinge verskil egter van dié in volwasse bolle en is nie deur VVG 0425 gedomineer nie. Verder was die meeste (≤ 60%) saad- en saailingisolate matig virulent, in teenstelling met die meestal hoogs virulente isolate uit volwasse bolle.

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Porto, Maria Alice Formiga. „Associação de Fusarium solani, Macrophomina phaseolina e Rhizoctonia solani causando podridão radicular em meloeiro sob efeito de adubos verdes“. Universidade Federal Rural do Semi-Árido, 2015. http://bdtd.ufersa.edu.br:80/tede/handle/tede/105.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The occurrence of root diseases is one of the main reasons of yield loss in melon crop, especially the pathogens that causes root and collar rot, as the fungi Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. and Rhizoctonia solani Kuhn, being observed in muskmelon either alone or associated. The use of crop residues and plant materil, besides the improvement in the physical properties of the soil, also favors microbial activity of the species presents in this environment and affects negatively onpathogens population. Therefore, the objective of this work was to evaluate the associations of F. solani, M. phaseolina and R. solani in the incidence and severity of root rot and fresh and dry weight of muskmelon and verify the effect of green manure in root rot caused by these pathogens alone or associated. The experiment was conducted in two stages, in a greenhouse. The first stage evaluated the association of F. solani, M. phaseolina and R. solani causing root rot in melon, using a randomized block design with 8 treatments (F. solani; M. phaseolina, R. solani, F. solani + M. phaseolina, F. solani + R. solani; M. phaseolina + R. solani, F. solani + M. phaseolina + R. solani; non-infested soil) and 8 repetitions with experimental unit of one pot (3.5 L) with 2 plants. The characteristics evaluated were the incidence of root rot in melon plants at the end of the cycle; disease severity based on a scale notes, and the fresh and dry weight of muskmelon. At the second stage, evaluated the effects of green manure in the association of these pathogens in muskmelon, which was conducted one experiment with Jack beans (Canavalia ensiformis L. DC) and another with Pearl millet (Pennisetum glaucum (L.) R. BR.). The experiments were performed simultaneously in a randomized block design with 8 x 4 factorial {8 types of fungi / association (M. phaseolina, R. solani, F. solani, M. phaseolina + R. solani; M. phaseolina + F. solani, R. solani + F. solani; M. phaseolina + R. solani + F. solani; non-infested soil), 4 forms of management [incorporated, in coverage, polyethylene film (mulching) and without managment]} and 4 repetitions. The characteristics evaluated were the incidence of root rot of melon plants at the end of the cycle, and the fresh and dry weight of muskmelon. The results of disease incidence were submitted to the non-parametric test of Kruskal-Wallis and the fresh and dry weight of muskmelon were analyzed by the Scott-Knott test, both with significance level of 5% of probability (α = 0.05%). At stage 1, the treatment with the three pathogens F. solani, M. phaseolina and R. solani associated resulted in lower incidence of plants with symptoms and was not statistically different from the control. The pathogen R. solani was the least prevalent in the associations. The lowest accumulation of fresh and dry matter happened when the soil was infested with Fusarium solani alone. At stage 2, Jack beans in coverage provided lower incidence of root rot in muskmelon with Fusarium solani alone and in triple association (F. solani +M. phaseolina and R. solani). The use of Pearl millet had no effect on root rot incidence in most treatments. In both experiments (Jack beans andPearl millet), Macrophomina phaseolina was the fungus that prevailed in almost all associations. Jack beans and millet did not increase the fresh and dry weight of muskmelon in most treatments
A ocorrência de doenças radiculares representa uma das principais causas de perda de rendimento na cultura do melão, com destaque para os patógenos causadores das podridões de raízes e colos, como os fungos Fusarium solani (Mart.) Sacc., Macrophomina phaseolina (Tassi) Gold. e Rhizoctonia solani Kuhn, sendo observados no meloeiro tanto de forma isolada quanto associada. A utilização de restos de cultura e material vegetal, além de melhorar as propriedades físicas do solo, favorece a atividade microbiana das espécies presentes neste ambiente e interfere negativamente sobre a população de patógenos. Portanto, objetiva-se com este trabalho avaliar as associações dos patógenos F. solani, M. phaseolina e R. solani na incidência e severidade de podridão radicular e na massa da matéria fresca e seca do meloeiro e verificar o efeito de materiais vegetais na podridão radicular causada por estes patógenos isolados ou associados. O experimento foi conduzido em duas etapas, em casa de vegetação, sendo que na primeira avaliou-se a associação de F. solani, M. phaseolina e R. solani causando podridão radicular em meloeiro, quando foi utilizado o delineamento em blocos casualizados com 8 tratamentos (F. solani; M. phaseolina; R. solani; F. solani + M. phaseolina; F. solani + R. solani; M. phaseolina + R. solani; F. solani + M. phaseolina + R. solani; solo não infestado) e 8 repetições, com unidade experimental de 1 vaso (3,5 L) com duas plantas. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, severidade da doença com base em escala de notas, além da matéria fresca e seca das plantas de melão. Na segunda etapa, foi avaliado o efeito de materiais vegetais na associação desses patógenos, também em meloeiro, onde foi realizado um experimento com Feijão-de-porco (Canavalia ensiformis L. DC) e outro com Milheto (Pennisetum glaucum (L.) R. BR.). Os experimentos foram conduzidos simultaneamente, em delineamento experimental de blocos casualizados, com esquema fatorial 8 x 4, sendo 8 tipos de fungos/associação (M. phaseolina; R. solani; F. solani; M. phaseolina + R. solani; M. phaseolina + F. solani; R. solani + F. solani; M. phaseolina + R. solani + F. solani; solo sem inoculação), 4 formas de manejo (incorporado, cobertura, mulching e sem manejo) e 4 repetições. As características avaliadas foram: incidência de podridão radicular nas plantas de melão no fim do ciclo, a massa da matéria fresca e seca das plantas de melão. Os resultados de incidência de doença obtidos foram submetidos ao teste não paramétrico de Kruskal-Wallis e a massa damatéria fresca e seca foram analisados pelo teste de Scott-Knott, ambos com nível de significância a 5% de probabilidade (α = 0,05%). Na etapa 1, o tratamento no qual foram associados três patógenos F. solani, M. phaseolina e R. solani propiciou menor porcentagem de plantas com sintomas da doença e não diferiu estatisticamente da testemunha. O fitopatógeno R. solani foi o que menos prevaleceu nas associações. Quando o solo foi infestado com Fusarium solani, isoladamente, o melão obteve baixo acúmulo de matéria fresca e seca. Na etapa II, o feijão-de-porco em cobertura proporcionoiu menor incidência de podridão radicular do meloeiro quando o Fusarium solani estava sozinho e em associação tripla (F. solani +M. phaseolina e R. solani). A utilização do milheto não apresentou efeito na incidência de podridão radicular na maioria dos tratamentos. Tanto na utilização do feijão-de-porco quanto do milheto, M. phaseolina foi o fungo que prevaleceu na maioria das associações nas quais estava presente. O feijão-de-porco e o milheto não proporcionaram aumento na massa da matéria fresca e seca do meloeiro na maioria dos tratamentos

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Gure, Abdella. „Seed-borne fungi of the afromontane tree species Podocarpus falcatus and Prunus africana in Ethiopia /“. Uppsala : Dept. of Forest Mycology and Pathology, Swedish Univ. of Agricultural Sciences, 2004. http://epsilon.slu.se/s334.pdf.

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Furtner, Bernhard. „Abiotic and biotic factors in the nutrient solution and filter skin (Schmutzdecke) of slow filters integrated to closed hydoponic greenhouse : potential predictors for assessment of efficacy /“. Alnarp : Department of Crop Science, Swedish University of Agricultural Sciences, 2006. http://epsilon.slu.se/10232320.pdf.

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Guimarães, Izabel Macedo. „Reação de germoplasmas de melão a Fusarium solani f. sp. cucurbitae e herança da resistência do acesso AC-33 a Monosporascus cannonballus“. Universidade Federal Rural do Semi-Árido, 2016. http://bdtd.ufersa.edu.br:80/tede/handle/tede/584.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The melon cultivation in semi-arid northeast in consecutive cycles has generated problems caused by fungi inhabitants of the soil, such as Fusarium solani and M. cannonballus. The use of resistant cultivars is an interesting measure for the management of the disease. For this reason, it is important identify sources of resistance and study their inheritance. The objectives of this work were: a) to evaluate the reaction of melon accessions to F. solani f. sp. Cucurbitae; b) to evaluate the reaction of accessions and study the inheritance of resistance of accession AC-33 to M. cannonballus. In the first experiment, we evaluated twenty-one accessions in a completely randomized design in greenhouse. Two isolates were inoculated fifteen days after sowing by the toothpick. The assessment was done Thirty days after inoculation with a scale scored from zero to four. The accessions AC-01, AC-09, AC-42, AC-45, AC-50 and the cultivar 'Doublon' are the most promising materials for use in breeding programs for resistance to F. solani or as rootstocks. In the second experiment, sixteen accessions and line OF-02 were evaluated in a completely randomized design. We used the isolated MC-16 to infestation of a mixture (1:1:1) with soil, peat, and sand previously sterilized with the addition of a concentration of 20 u.f.c./g soil. The evaluation was performed at 45 days using a rating scale (1-5). In the third experiment, we investigated the inheritance of resistance of accession AC-33 crossed with line OF-02 (susceptible). We observed variability in the germplasm investigated for reaction to the fungus. The AC-33 is highly resistant to access M. cannonballus and its resistance is controlled by a major gene with additive and dominant effects and polygenes with additive effects
O cultivo do meloeiro no semiárido nordestino em ciclos consecutivos tem gerado problemas causados por fungos habitantes do solo, como Fusarium solani e Monosporascus cannonballus. O uso de cultivares resistentes é uma medida interessante para o manejo da doença. Em razão disso, é importante que fontes de resistência sejam identificadas e se conheça a herança da resistência. Os objetivos do presente trabalho foram: a) avaliar a reação de acessos de meloeiro a F. solani f. sp. cucurbitae e b) avaliar a reação de acessos e estudar a herança da resistência do acesso AC-33 a M. cannonballus. No primeiro experimento, foram avaliados 21 acessos em um delineamento inteiramente casualizado em casa-de-vegetação. Foram inoculados dois isolados, com o método do palito, aos 15 dias após a semeadura. A avaliação dos acessos foi realizada 30 dias após a inoculação, com uma escala de 0 a 4. Os acessos AC-01, AC-09, AC-42, AC-45 e AC-50 e a cultivar ‘Doublon’ são os materiais mais promissores para uso em programas de melhoramento genético visando à resistência a F. solani ou como porta-enxertos. No segundo experimento, foram avaliados 16 acessos e a linhagem OF-02 em um delineamento inteiramente casualizado. Utilizou-se o isolado MC-16 para infestação de mistura em volume de 1:1:1 de terra, turfa e areia, previamente esterilizada com a adição de uma concentração 20 u.f.c./g de solo. A avaliação foi realizada aos 45 dias utilizando uma escala de notas (1 a 5). No terceiro experimento, investigou-se a herança da resistência do acesso AC-33 (resistente) cruzado com a linhagem OF-02 (suscetível). Observou-se a existência de variabilidade no germoplasma investigado para reação ao fungo. O acesso AC-33 é altamente resistente a M. cannonballus e sua resistência é controlada por um gene maior de efeito aditivo e dominante e poligenes de efeitos aditivos
2017-01-10

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Silva, Larissa Chariel Domingos da. „Bioprospecção de isolados de leveduras e bactérias, provenientes da secreção oral de Diatraea saccharalis (Fabricius, 1794) (Lepidoptera: Crambidae) coletada em campo, antagônicos a Fusarium verticillioides (Nirenberg, 1976) e Colletotrichum falcatum (Went, 1893)“. Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8002.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Insect symbionts may have unknown functions in the interaction between insect-plant and insect with microorganisms that co-inhabit the same space. The objective of this study was to investigate the antagonism potential of symbiont microbiota from oral secretion D. saccharalis collected in the field, against Fusarium verticillioides and Colletotrichum falcatum pathogens commonly found inside the cane. For this, 4° and 5° instar caterpillars were collected inside sugarcane varieties RB-835 054 and SP- 813 250, and brought to the lab inside the cane stalks. The microbiota of oral secretion was transferred to two selective media, NA (nutrient agar) for bacteria and DRBC (dicloran Rose Bengal Chloramphenicol) for yeast. Based on morphology and coloration of the colonies twenty colonies of bacteria and yeast were selected. Four culture media were tested in co-cultivation of F. verticillioides and C. falcatum versus bacteria or yeast isolates: PDA (potato, dextrose, agar), YEPD (yeast extract, peptone, dextrose), CCS (supplemented cane broth) and NA (Nutrient Agar). The most suitable culture medium for growth of most microorganisms was BDA. Antagonism potential of 82 bacterial isolates and 87 yeast isolates to C. falcatum and F. verticillioides was assessed using a visual scale of categories 1 to 4, with 4 being the maximum degree of antagonism. Isolates that allocated category greater than or equal to 2 were evaluated in co-culture with C. falcatum and F. verticillioides as the percentage of growth inhibition. It was possible to identify four isolates of bacteria which have the potential to inhibit growth of pathogens and 9 isolates with the same potential but with much lower percentages. These results demonstrate that some isolates of bacteria and yeast may influence the relationship between the bit-rot complex and sugarcane plant, may in future be used as a biological control of these pathogens or have some molecules of biotechnological interest extracted and purified.
Simbiontes de insetos podem ter funções desconhecidas na interação entre insetoplanta e do inseto com microrganismos que co-habitam o mesmo espaço. O objetivo desse estudo foi investigar o potencial de antagonismo da microbiota simbionte, presentes na secreção oral de Diatraea saccharalis, com os fitopatógenos Fusarium verticillioides e Colletotrichum falcatum que habitam o colmo de cana-de-açúcar. Para isso, foram coletadas, nas variedades de cana RB-835054 e SP-813250, lagartas de 4° e 5° instar e trazidas para o laboratório junto aos toletes de cana. A microbiota da secreção oral foi transferida para dois meios de cultura seletivos, NA (nutrient agar) para bactérias e DRBC (Dicloran Rosa-de-Bengala Cloranfenicol) para leveduras. Baseado na morfologia e coloração das colônias, foram selecionadas, vinte colônias de bactéria e também de levedura de 5 lagartas. Foram testados quatro meios de cultura: BDA (batata, dextrose, agar), YEPD (yeast extract, peptone, dextrose), CCS (caldo-de-cana suplementado) e NA para os testes de cultivo pareado. O meio de cultura mais adequado para o crescimento da maioria dos microrganismos foi o BDA. O potencial de antagonismo de 82 isolados de bactéria e 87 isolados de levedura a C. falcatum e F. verticillioides foi avaliado através de uma escala visual de categorias de 1 a 4, sendo 4 o grau máximo de antagonismo. Os isolados a que foi atribuída categoria maior ou igual a dois foram avaliados em co-cultivo com C. falcatum e F. verticillioides quanto à porcentagem de inibição do crescimento. Foi possível identificar 4 isolados de bactéria que tem o potencial de inibir o crescimento dos fitopatógenos e 9 isolados com o mesmo potencial, porém com porcentagens menores. Esses resultados demonstram que alguns isolados de bactérias e leveduras podem influenciar na relação existente entre o complexo broca-podridão e a planta de cana-de-açúcar, podendo, futuramente, serem utilizados como controle biológico desses fitopatógenos ou terem algumas moléculas de interesse biotecnológico extraída e purificada.

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Muleta, Diriba. „Microbial inputs in coffee (Coffea arabica L.) production systems, southwestern Ethiopia : implications for promotion of biofertilizers and biocontrol agents /“. Uppsala : Dept. of Microbiology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/2007117.pdf.

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Visser, Marinda. „Molecular biological studies of the Fusarium wilt pathogen of banana in South Africa“. Thesis, Pretoria [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-04042005-144251.

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Whitehead, Debra Sian. „Races and pathotypes of the wilt pathogen Fusarium oxysporum“. Thesis, University of East Anglia, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293758.

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Vermeulen, Meagan. „A host-pathogen study of Fusarium Verticillioides in resistant and susceptible maize inbred lines“. Thesis, Stellenbosch : Stellenbosch University, 2015. http://hdl.handle.net/10019.1/96915.

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Thesis (MSc)--Stellenbosch University, 2015
ENGLISH ABSTRACT: Maize (Zea mays L.) is an important crop worldwide and forms the staple diet of many African countries including South Africa. Fusarium ear rot (FER) of maize is caused by a fungus, Fusarium verticillioides, which also produces the fumonisin mycotoxin group. The consumption of fumonisin contaminated maize grain has been associated with serious human and animal health complications. Several South African maize inbred lines exhibiting resistance to FER and fumonisin contamination have been identified. These locally adapted inbred lines could be used to generate mapping populations to identify QTLs associated with resistance to FER and fumonisin contamination. The corresponding markers could be utilised in breeding programmes through marker-assisted selection to ensure the development of commercial cultivars with resistance to FER and fumonisin contamination. In this study, resistant and susceptible maize inbred lines were utilised to commence the development of recombinant inbred line (RIL) populations for the mapping and validation of QTLs associated with FER and fumonisin resistance. One F2 population was phenotypically and genotypically analysed to produce a linkage map for the preliminary identification of QTLs associated with resistance to F. verticillioides infection and fumonisin deposition. A potential QTL for resistance to FER was detected and should be validated across several locations and years in the subsequent RIL population. Additionally, potential resistance barriers of maize to infection by F. verticillioides were investigated by histological studies. The importance of a closed stylar canal in determining resistance to FER was established for nine South African maize inbred lines by means of scanning electron microscopy (SEM). No significant association was observed between a closed stylar canal and the resistance/susceptible status of maize inbred lines before pollination, while the canals appeared closed in all inbred lines following pollination. The results suggest that the stylar canal architecture is not an essential factor determining resistance to F. verticillioides ingress in the maize inbred lines selected for this study. Furthermore, the possibility of resistance to FER and fumonisin contamination being initiated during the seedlings phase of a resistant and susceptible maize inbred line was investigated by means of confocal laser scanning microscopy (CLSM). Fusarium verticillioides growth originating from soil-borne or seed-borne contamination was monitored in various above and below soil plant tissues but no significant difference in the colonisation could be determined between resistant and susceptible maize seedlings. No fumonisin was produced regardless of the inoculation method or resistance status of the plant. These results suggests that the resistant and susceptible maize seedlings used in this study may not be resistant to systemic fungal ingress but may resist the deposition of fumonisins. The resistance associated with the resistant inbred line is not mediated during the seedling phase but potentially through structural and biochemical defence mechanisms during later plant developmental stages.
AFRIKAANSE OPSOMMING: Mielies (Zea mays L.) is ‘n belangrike graangewas wat wêreldwyd geproduseer word en dien as stapelvoedsel in talle Afrika-lande, insluitend Suid-Afrika. Fusarium kopvrot (FKV) in mielies word veroorsaak deur die swam, Fusarium verticillioides, wat ook die fumonisien mikotoksien groepe produseer. Die inname van fumonisien-geïnfekteerde mielies gaan gepaard met ernstige gesondheidsprobleme in mense en diere. Verskeie Suid-Afrikaanse ingeteelde mielielyne, wat weerstandbiedend is teen FKV en fumonisien kontaminasie, is voorheen identifiseer. Hierdie plaaslik-aangepaste teellyne kan gebruik word om kartering populasies te genereer om kwantitatiewe eienskap loci (KEL) te identifiseer wat verband hou met weerstandbiedenheid teen FKV en fumonisien kontaminasie. Die ooreenstemmende merkers kan gebruik word in teelprogramme deur gebruik te maak van merker-geassisteerde seleksie om kommersieële kultivars, wat weerstandbiedend is teenoor FKV en fumonisien kontaminasie, te ontwikkel. In hierdie studie is weerstandbiedende en vatbare mielie inteellyne gebruik om rekombinante inteellyn (RIL) populasies te begin ontwikkel vir die kartering en validasie van KEL’e geassosieer met FKV en fumonisien weerstandbiedenheid. Een F2 populasie was fenotipies en genotipies geanaliseer om ‘n koppeling-kaart te verwek vir die voorlopige identifikasie van KEL’e geassosieer met weerstandigheid tot F. verticillioides infeksie en fumonisein afsetting. ‘n Potensiële KEL vir weerstandbiedenheid is geïdentifiseer, wat verdere bevestiging in die daaropvolgende RIL populasie in verskeie geografiese areas en oor addisionele seisoene, benodig. Potensiële fisiese versperrings teen F. verticillioides tydens mieliesaad infeksie is ook ondersoek met behulp van histologiese studies. Die belangrikheid van ‘n geslote styl-kanaal vir weerstandbiedendheid teenoor FKV is bevestig in nege Suid-Afrikaanse inteellyne deur middel van skandeer elektron mikroskopie (SEM). Geen beduidende verwandskap tussen ‘n geslote styl-kanaal en die weerstandbiedenheid/vatbaarheid van die inteellyne voor bestuiwing is gevind nie, terwyl die kanaal in alle inteellyne gesluit was na bestuiwing. Die resultate dui daarop dat die styl-kanaal argitektuur nie ‘n noodsaaklike faktor is in die bepaling van weestand tot F. verticillioides besmetting in die suiwer mielielyne wat geselekteer was in hierdie studie nie. Verder is die moontlikheid dat weestand tot FKV en fumonisien kontaminasie geïnisieer kan word gedurende die saailing-fase ondersoek in beide ‘n weerstandbiedende en vatbare mielie inteellyn met behulp van konfokale laser skandering mikroskopie (CLSM). Die groei van F. verticillioides afkomstig vanuit die grond of saad is gemonitor in verskeie bo- en ondergrondse plantweefsels, maar geen beduidende verskille in kolonisasie kon opgespoor word tussen weerstandbiedende en vatbare mielie saailinge nie. Geen fumonisien produksie is waargeneem nie, ongeag die innokulasie metode of weerstand-status van die plant. Hierdie resultate dui daarop dat die weerstandbiedende en vatbare mielie saailinge wat in hierdie studie gebruik is moontlik nie weerstandbiedend is teen sistemiese swaminfeksie nie, maar wel weerstand kan bied tot afsetting van fumonisiene. Die weerstand geassosieër met die weerstandbiedende inteellyn word nie bemiddel gedurende die saailingfase nie maar waarskynlik deur strukturele en biochemiese verdedigingsmeganismes tydens latere plant ontwikkelings-stadia.
National Research Foundation (NRF)

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Wilkinson, Kendle. „Comparative studies of pathogenic and non-pathogenic strains of Fusarium oxysporum in relation to developing disease management strategies for fusarium wilt in banana /“. St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17346.pdf.

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Picot, Adeline. „Modulation de la production des fumonisines sur épis de maïs : influence des composantes physiologiques et biochimiques du grain et des événements de contamination mutiple“. Paris 11, 2010. http://www.theses.fr/2010PA112326.

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Fusarium verticillioides est un des champignons responsables de la fusariose sur maïs. Sur épi, cette espèce est capable de produire des fumonisines, métabolites secondaires stables, dont la toxicité pour l'homme et les animaux est documentée. Actuellement, aucun procédé ne permet d'éliminer les fumonisines dans les grains après récolte. Limiter leur occurrence implique de limiter leur biosynthèse au champ. Parmi les facteurs modulant la biosynthèse des fumonisines, l'évolution des composantes physiologiques et biochimiques du grain ainsi que les événements de contamination multiple semblent être déterminants. La majorité des études concernant le rôle de ces facteurs sur la biosynthèse des fumonisines a été menée in vitro. Pour clarifier leurs effets potentiels in planta, une approche au champ a été menée. La cinétique d'infection et d'accumulation de fumonisines in planta confirme les études réalisées sur grains et suggère que l'évolution du pH et du contenu du grain en amylopectine pendant le stade denté favoriserait la production des fumonisines. Un effet inhibiteur des tocophérols, composés biochimiques du maïs, sur la production de fumonisines a aussi été démontré in vitro. Cette inhibition demande à être validée in planta. En outre, l'étude d'inoculations mixtes ou en décalage a mis en évidence que des épis colonisés par F. Graminearum favoriseraient l'infection de F. Verticillioides. Des études de compétition réalisées in vitro indiquent que la production de fumonisines peut être augmentée en présence de F. Graminearum sans induire un gain de compétitivité. Nos travaux ouvrent de nouvelles perspectives sur les mécanismes impliqués dans la régulation des fumonisines
Fusarium verticillioides is a fungus responsible for maize ear rots. During ear colonization, this fungus is able to produce fumonisins, stable secondary metabolites which toxicity on animals and humans is documented. No treatments that eliminate fumonisin content during processing are available. Control strategies mainly consist in managing this disease in fields. Among the factors that modulate fumonisin biosynthesis, the evolution of physiological and biochemical components occurring during ripening seems to be crucial. Additionally, the interactions with F. Graminearum may also modify the colonization dynamic and fumonisin accumulation. Most studies dealing with the impact of these factors on fumonisin biosynthesis have been performed in vitro. To clarify their potential effects in planta, field experiments have been carried out. Our kinetics study on fungal growth and fumonisin accumulation confirm results obtained on maize kernels and suggests that the evolution in kernel pH and amylopectin content may enhance fumonisin biosynthesis. Additionally, an inhibitory effect of tocopherols, maize biochemical compounds, has been shown in vitro towards fumonisin biosynthesis. This effect has yet to be confirmed in planta. Besides, results obtained with mixed and sequential inoculations with F. Graminearum gave evidence that maize ears colonized by F. Graminearum may be an infection pathway for F. Verticillioides. Ln vitro studies also showed that fumonisin production was sometimes enhanced with the presence of F. Graminearum but without inducing an increase in competitiveness. Overall, our results provide new perspectives for the mechanisms involved in fumonisin regulation

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Poudel, Bikash. „Understanding Host Resistance and Pathogen Biology in the Wheat-Fusarium graminearum Pathosystem“. Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/31811.

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Fusarium head blight (FHB) is a major challenge in global wheat production. In the United States, the disease is predominantly caused by the fungus Fusarium graminearum. Utilization of FHB-resistant wheat cultivars integrated with other measures such as fungicide application is the most effective approach for the management of this disease. This study aimed to 1) identify novel quantitative trait loci (QTL) for resistance to FHB in a Brazilian spring wheat cultivar ‘Surpresa’ through bi-parental mapping, 2) detect QTL for FHB resistance in a global panel of 233 spring wheat accessions by genome-wide association analysis (GWAS), and 3) localize genomic regions governing traits associated with virulence in Fusarium graminearum. Using phenotypic and genotypic data from 187 recombinant inbred lines derived from the cross between Surpresa and a susceptible spring wheat cultivar ‘Wheaton’, four QTL (Qfhb.ndwp-2AS, Qfhb.ndwp-2AL, Qfhb.ndwp-3B, and Qfhb.ndwp-4D) were mapped on chromosomes 2A, 3B, and 4D of Surpresa, respectively. Qfhb.ndwp-2AS, Qfhb.ndwp-2AL, and Qfhb.ndwp-3B were found to be novel based on physical locations of the markers tightly linked to these QTL. Two significant marker-trait associations (Qfhb.ndwp-3A and Qfhb.ndwp-2BL) were detected by GWAS of 233 spring wheat accessions, which conferred type II and type III FHB resistance and mapped on chromosomes 3A and 2B, respectively. Both QTL were novel based on the physical locations of tightly linked markers. GWAS of virulence and fungicide sensitivity using 183 F. graminearum isolates collected from North Dakota identified two significant marker-trait associations in chromosomes 1 and 3 for virulence, and two for fungicide sensitivity. The genes associated with virulence that were detected in this study were not previously reported. Identification of these novel genes in metabolic pathways of F. graminearum could help to develop new strategies for the management FHB.

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Eparvier, Agnès. „Compétition entre Fusarium pathogènes et Fusarium non pathogènes pour la colonisation des tissus racinaires : mise au point et utilisation de techniques sérologique et génétique de marquage“. Lyon 1, 1992. http://www.theses.fr/1992LYO10273.

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La competition entre fusarium pathogenes et fusarium non pathogenes pour la colonisation des tissus racinaires est un des modes d'action impliques dans l'interaction entre fusarium. Afin de caracteriser l'aptitude colonisatrice de differentes souches de f. Oxysporum, et de suivre leur developpement dans les racines, des techniques de marquage specifique permettant la quantification et la visualisation du champignon ont du etre developpees. La production d'anticorps polyclonaux et monoclonaux anti-fusarium, et la transformation de 2 souches de f. Oxysporum par le systeme de genes gus (codant pour la glucuronidase) ont ete retenues. Les anticorps produits reconnaissent la plante infectee, et donnent une reponse minimum avec la plante saine, mais la specificite de souche escomptee n'a pas ete obtenue. La transformation des souches, pathogene et non pathogene, par le systeme gus a produit des mutants stables et exprimant une activite glucuronidase elevee, directement correlee a l'activite metabolique de la souche. L'utilisation conjointe de ces 2 outils a permis de mesurer la densite et l'activite des populations fusariennes au niveau racinaire. Un comportement variable des souches de f. Oxysporum a ete mis en evidence: les souches presentent des cinetiques de colonisation analogues mais avec des intensites et des vitesses de colonisation variables. Par ailleurs, une grande diversite de l'aptitude des souches non pathogenes a inhiber l'activite de la souche pathogene a ete observee. Les mecanismes d'action impliques dans l'interaction entre fusarium different suivant les souches non pathogenes considerees. Une etude histologique, utilisant les outils mis au point, devraient permettre des progres importants dans l'analyse des mecanismes de competition entre fusarium pour les tissus racinaires

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Sagaram, Uma Shankar. „Molecular characterization of genes regulating fumonisin biosynthesis and development in maize pathogen fusarium verticilliodes“. Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1361.

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Lin, Binbin. „Movement and Structure of Atmospheric Populations of Fusarium“. Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23203.

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Fusarium is one of the most important genera of fungi on earth. Many species of Fusarium are well-suited for atmospheric dispersal, yet little is known about their aerobiology. Previous research has shown that large-scale features known as atmospheric transport barriers (Lagrangian coherent structures) guide the transport and mixing of atmospheric populations of Fusarium. The overall goal of this work is to expand our knowledge on the movement and structure of atmospheric populations of Fusarium. The first objective was to monitor changes in colony forming units (CFUs) in atmospheric populations of Fusarium over small time intervals (10 min to several hours). We hypothesized that consecutive collections of Fusarium with unmanned aerial vehicles (UAVs) demonstrate small variations in colony counts. To test this hypothesis, sampling devices on UAVs were separated into two groups, four inner sampling devices opened during the first 10 minutes and four outer sampling devices opened during the second 10 minutes. Results indicated that (1) consecutive collections of Fusarium at 100 m demonstrated small variations in counts and (2) the similarity between collections decreased as the time between sampling intervals increased. The second objective was to determine the structure of atmospheric populations of Fusarium species and relate this to potential source regions. We hypothesized that diverse atmospheric populations of Fusarium are associated with multiple source regions. To test this hypothesis, Fusarium samples were collected with UAVs and identified to the level of species by sequencing a portion of the translation elongation factor 1-alpha gene (TEF-1•). Potential source regions were identified using the atmospheric transport model HYSPLIT. Results indicated that (1) diverse atmospheric populations of Fusarium appeared to be associated with multiple source regions, and (2) the number of Fusarium species collected with UAVs increased with back-trajectory distance of the sampled air. The third objective was to examine the associations between concentrations of populations of Fusarium at ground level (1 m) and in the lower atmosphere (100 m). We hypothesized that concentrations of Fusarium in the atmosphere vary between 1m and 100m. To test this hypothesis, Fusarium was collected with a Burkard volumetric sampler (BVS) and UAVs. Colony counts were converted to spore concentrations (spores per cubic meter of air). Sampling efficiency was used to correct spore concentrations. Results indicated that (1) the distribution of spore concentrations was similar for both samplers over different times of the day, (2) spore concentrations were generally higher in the fall, spring, and summer, and lower in the winter, and (3) spore concentrations were generally higher with BVS samplers than those with UAVs for both hourly and seasonal data. The fourth objective was to assess the ability of strains of Fusarium collected in the lower atmosphere to cause plant disease. We hypothesized that certain isolates of Fusarium collected with UAVs cause plant diseases. To test this hypothesis, we randomly selected isolates of three different species (F. circinatum, F. avenaceum, and F. sporotrichioides) of Fusarium collected with UAVs to inoculate three different hosts (wheat, corn, and pine). Known Fusarium strains were obtained from J. Leslie at Kansas State University as controls. Results indicated showed that the three different isolates tested were able to cause plant diseases in three different hosts (wheat, corn, and pine), confirming that these were potential agents of disease. This work sets the stage for future work examining potential source regions, transport distances, and seasonal patterns of Fusarium. An increased understanding of the dynamics and population structure of plant pathogenic Fusarium in the lower atmosphere is essential for predicting the spread of plant disease and optimizing disease management strategies in the future.
Ph. D.

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Bian, Zhuyun. „Characterization of Effector Encoding Genes from the Novel Sugar Beet Pathogen Fusarium Secorum“. Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27711.

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A new disease of sugar beet, named Fusarium yellowing decline, was recently found in in the Red River Valley of MN and ND. This disease is caused by a novel pathogen named Fusarium secorum. Pathogens such as F. secorum secrete proteins during infection called ?effectors? that help establish disease. Since pathogenicity and disease development may depend on effector proteins produced by F. secorum during infection, effector protein identification furthers our understanding of the biology of this important pathogen. A list of 11 candidate effectors was generated previously. In this study, to characterize putative effectors, we developed a transformation system using polyethylene glycol?mediated transformation. Several mutant lines were created with an effector deleted from the genome using a split-marker knock-out strategy. To explore their role in pathogenicity, mutant strains have been inoculated to sugarbeet and compared to WT F. secorum.

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Mbofung, Gladys Chia. „Phylogeny, Molecular Detection, and Genetic Variation of Fusarium oxysporum, Vascular Wilt Pathogen of Lettuce“. Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/194000.

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This work encompasses studies on the phylogeny of F. oxysporum f. sp. lactucae, the development of a PCR-based seed assay for the detection of this fungus in seed, the potential of seed transmission of the fungus that may result in seed dissemination, and the genetic variation existing within pathogen populations. In phylogenetic analysis, the mtSSU and EF-1α sequences provided limited phylogenetic resolution and did not differentiate the lactucae isolates from other F. oxysporum isolates, while the IGS region resolved lactucae race 1 isolates as a monophyletic group with three other f. spp. of F. oxysporum. In all analyses, lactucae race 2 isolates comprised a separate lineage that was phylogenetically distinct. Based the IGS, PCR primers were designed for detection of the fungus, and a PCR-based seed assay was developed for detection of the fungus in seed. This assay allowed for detection of the pathogen from artificially infested seed lots with infestation rates as low as 0.5%. To investigate seedborne transmission, the moderately resistant cultivars Sharpshooter, Vulcan, and King Henry were inoculated and grown to maturity in the greenhouse. The pathogen was recovered from sections of surface disinfested inflorescence stalks at rates of 14.3 - 62.7% but not from the floral parts. The incidence of recovery from nondisinfested seeds was between 0.02% and 0.08%. The pathogen was not isolated from surface disinfested seeds suggesting that it was externally seedborne. The pathogen was recovered from pathogen-free seeds mixed with infested debris suggesting infested seed may contribute to recently documented dissemination of this pathogen worldwide. Isolates of Fusarium oxsyporum f. sp. lactucae were analyzed for genetic diversity using inter-simple sequence repeat molecular markers. Results revealed 2 main groups within the Arizona isolates corresponding to eight haplotypes in 2005, which evolved from 2 haplotypes in 2001. Haplotype 1-05 was widespread, occurring in two of the four countries where F. o. f. sp. lactucae has been reported. 23 haplotypes were identified among the California isolates that clustered into two subgroups. The clustering of isolates from Arizona suggests that there has been more than one introduction of the pathogen into Arizona.

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Matheron, Michael E., und Martin Porchas. „Examination of Soil Solarization as a Management Tool for Fusarium Wilt of Lettuce: 2005 Field Trial“. College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/215031.

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Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this first discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from approximately 30 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Cultural disease control measures, such as extended soil flooding and soil solarization, have shown promise in managing Fusarium wilt in other cropping systems. The specific research objective during the 2005 growing season was to further evaluate the effect of preplant solarization of planting beds on subsequent development of Fusarium wilt on lettuce. There was no significant difference between the short (28 days) and long (56 days) solarization period in the subsequent number of diseased lettuce plants; therefore, the disease incidence values for both solarization periods were combined and compared to nonsolarized plots. At each data collection date, the number of lettuce plants showing symptoms of Fusarium wilt was significantly lower in solarized beds compared to nonsolarized beds. At plant maturity (Nov 18), Fusarium wilt had claimed virtually all lettuce plants of the cultivar 'Lighthouse' growing in nonsolarized soil; however, only 19% of lettuce plants of the same cultivar growing in solarized soil showed disease symptoms. This equates to an 81% reduction in diseased plants in solarized soil compared to nonsolarized soil. The results of this field trial suggest that a 30-day summer solarization treatment of lettuce beds can significantly reduce the inoculum of Fusarium oxysporum f. sp. lactucae to levels that would allow substantial growth of a susceptible lettuce cultivar. Additional field studies are needed to refine the solarization process to potentially achieve further increases in efficiency of destroying propagules of Fusarium oxysporum f. sp. lactucae in infested fields.

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DUBOIS, MARIE-PIERRE. „Etude de la variabilite genetique de fusarium oxysporum f. Sp. Vasinfectum, champignon pathogene du cotonnier“. Paris 11, 1997. http://www.theses.fr/1997PA112325.

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Une etude de la diversite genetique de fusarium oxysporum f. Sp. Vasinfectum (fov), champignon responsable de la fusariose du cotonnier a ete realisee. La mise au point de marqueurs moleculaires rapd et rflp, et l'utilisation de l'electrophorese en champs pulses, a permis d'analyser la variabilite genomique de pupulations de fov. A une echelle macrogeographique, l'analyse d'une collection de 52 souches de fov provenant de diverses regions de culture du cotonnier dans le monde a montre que les populations de fov sont structurees en au moins 4 lignees clonales a large distribution geographique. La lignee 3 rassemble les isolats de la race 3, distribues uniquement en egypte, en israel et au soudan. Les isolats appartenant a la lignee 4 proviennent d'asie et rassemblent les isolats de la race 4. Les isolats appartenant aux lignees a1 et a2 sont presents en afrique et en amerique, et appartiennent a la race a. De plus, une importante variabilite chromosomique au sein de la forme speciale vasinfectum, suggerant une grande plasticite du genome de fov, a ete mise en evidence suite a l'etablissement de caryotypes electrophoretiques des souches et a l'analyse de la distribution d'elements transposables (fot 1, fot 2, impala, foret 1). A une echelle microgeographique (le soudan), une tres forte homogeneite genetique des souches a ete mise en evidence montrant clairement que cette population est clonale et forme une seule lignee genetique. De plus, il a ete montre par des tests de pouvoir pathogene, que seule la race 3 etait presente dans ce pays. La souche r5 decrite comme nouvelle race ne serait qu'un variant moins agressif de la race 3.

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Matheron, Michael E., und Martin Porchas. „Further evaluation of Soil Solarization as a Management Tool for Fusarium Wilt of Lettuce: 2006 Field Trial“. College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2008. http://hdl.handle.net/10150/215033.

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Fusarium wilt of lettuce was first recognized in Arizona in 2001. Since this initial discovery, the pathogen, Fusarium oxysporum f.sp. lactucae (Fol), has been recovered from infected lettuce plants from over 40 different fields. This fungus is a soil-borne pathogen that can remain viable in soil for many years. Soil solarization has shown promise in managing Fusarium wilt in other cropping systems as well as in lettuce field trials conducted during 2004 and 2005. In an effort to maximize the solarization effect on subsequent disease development, the following factors were evaluated in a 2006 field trial: 1) solarization of unshaped versus preshaped beds, 2) the effect of soil moisture on solarization efficiency of preshaped beds, and 3) effect of lettuce type on Fusarium wilt incidence after solarization. The entire field was flood irrigated on Jun 21. Plots were solarized during Jul and/or Aug by covering beds with 1-mil thick clear plastic. During the solarization treatment from Jul 3 to Sep 10, the mean soil temperature in preshaped solarized beds at a depth of 2 and 9 inches was 116 and 95°F, respectively, and 102 and 97°F, respectively, in beds not covered with plastic. When solarization was initiated 15 days after soil irrigation, a 20% reduction in Fusarium wilt was recorded for a crisphead lettuce cultivar grown on solarized unshaped beds compared to a 56% reduction in disease when the same crisphead cultivar was grown on preshaped solarized beds. There was no significant difference between a one and two month solarization period in the subsequent number of diseased lettuce plants. Solarization of preshaped beds 15 days after irrigation for one month reduced Fusarium wilt on crisphead lettuce by 56%, whereas the same solarization period initiated seven days after irrigation resulted in a 96% reduction of disease. The same one-month solarization period started one week after soil irrigation reduced the incidence of Fusarium wilt on green leaf (Two Star) and romaine (Green Towers) by 97 and 88%, respectively, compared to plants grown on unsolarized beds. The data show that summer solarization of moist soil can 1) destroy propagules of Fusarium oxysporum f. sp. lactucae in infested fields and 2) be a useful cultural management tool to significantly reduce the incidence of Fusarium wilt in a subsequent crop of lettuce.

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Duggal, Arti. „Molecular identification of Fusarium species occurring on white pine seedlings and methods to differentiate pathogenic and nonpathogenic isolates of Fusarium oxysporum f.sp. pini“. Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ35151.pdf.

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Laurent, Benoit. „Base génétique et potentiel d’évolution de la pathogénicité de Fusarium graminearum, bio-agresseur fongique des céréales“. Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0317/document.

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Le champignon Fusarium graminearum est l'un des principaux agents responsables de la fusariose des épis, une maladie nécrosante des céréales associée à une contamination des grains et des aliments par des mycotoxines. De récentes observations suggèrent une évolution de l’agressivité des populations de ce pathogène, questionnant l’efficacité et la durabilité des moyens de luttes actuels. Mieux anticiper cette évolution nécessite une meilleure caractérisation de la diversité phénotypique et génotypique existante entre souches. Six nouveaux génomes de F. graminearum ont été séquencés et ont permis l’identification et la caractérisation de 243 000 variations génétiques. La majorité de ces variants (77%) est concentrée dans des îlots de polymorphisme, représentant 32% du génome et enrichis en probables effecteurs liés à la pathogénicité de F. graminearum. La construction d’une population recombinante, et son génotypage avec 1 300 marqueurs moléculaires, ont permis le développement de la première carte génétique à haute-densité de l’espèce. La corrélation entre le taux de recombinaison et le polymorphisme a mis en évidence une organisation « à deux-vitesses » du génome de cette espèce. Finalement, l’intégration de ces données dans une approche de génétique quantitative a permis l’identification d’un locus polymorphe, affectant le gène FgVeA, et responsable de 90% de la variation d’agressivité et de la production de mycotoxine observée. Les différents résultats obtenus durant ces travaux font l’objet d’une discussion générale sur le potentiel adaptatif et d’évolution de ce pathogène
F. graminearum is one of the main causal agents of the fusarium head-blight (FHB), a cereal disease leading to head necrosis, in addition to grain and food/feed contamination by stable and toxic metabolites. Recent observations refer to an increase of pathogenicity, questioning efficiency and durability of current management practices. In order to anticipate this evolution, we must bring a deeper characterization of the currently existing diversity. Six new genomes of F. graminearum were sequenced, and 243,000 genetic variations have been identified and characterized. Seventy seven percent of the total number of the variants was located within 32% of the genome, delineating highly polymorphic islands. These islands are enriched with probable effectors linked to Fusarium’s pathogenicity. The construction and the genotyping on 1,300 molecular markers of a recombinant population have enabled the development of the first high-density genetic map of the species. The remarkable correlation between polymorphism and recombination rate highlighted the 'two-speed' genome organization of this pathogen. Finally, the integration of these data through a quantitative genetic approach allowed the discovery of one quantitative trait locus, likely to affect the gene FgVeA, and responsible for 90% of the observed variation of aggressiveness and mycotoxin production. These results are discussed in the light of F. graminearum’s adaptive potential and evolution

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Moine, Lauriane. „Identification et détection d'une nouvelle espèce de Fusarium pathogène sur la tomate de serre en Amérique du Nord“. Thesis, Université Laval, 2013. http://www.theses.ulaval.ca/2013/30331/30331.pdf.

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Récemment, un nouvel agent pathogène a causé d’importants dommages sur la tomate de serre dans un complexe au centre du Québec et au nord des États-Unis. À partir d’échantillons de plants infectés, des colonies produisant des macroconidies typiques de Fusarium spp. ont systématiquement été isolées. Le séquençage des régions ITS et tef de ces isolats, suivi de tests de pathogénicité, ont permis d’identifier Fusarium striatum comme l’agent pathogène. Il s’agit du premier rapport de cet agent pathogène au Canada. Suite à son identification, un test de dépistage moléculaire a été mis au point afin de détecter l’agent pathogène directement à partir des tissus végétaux. Les amorces développées ont été suffisamment spécifiques et sensibles pour détecter l’agent pathogène avant même l’apparition des symptômes. Nos résultats semblent indiquer que l’inoculum de F. striatum aurait été introduit dans les deux complexes de serre par les transplants provenant de leur fournisseur commun.

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Van, Nguyen Thuat [Verfasser], und Wilhelm [Akademischer Betreuer] Schäfer. „Signal transduction pathways in the fungal wheat pathogen Fusarium graminearum / Thuat Van Nguyen. Betreuer: Wilhelm Schäfer“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1032990406/34.

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Malligan, Cassandra D. „Crown rot (fusarium pseudograminearum) symptom development and pathogen spread in wheat genotypes with varying disease resistance“. University of Southern Queensland, Faculty of Sciences, 2009. http://eprints.usq.edu.au/archive/00006225/.

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[Abstract]Crown rot, caused by Fusarium pseudograminearum (Fpg), is an important soilborne disease of wheat and barley. The degree of crop damage depends on seasonal conditions. Typically, high moisture conditions early in the season encourage seedling infection from stubble residues. Moisture stress later in the season leads to the production of unfilled “whiteheads”. Current control relies on cultural practices and sowing of partially resistant varieties. In order to understand the nature of partial resistance, I have examined the patterns of disease symptom development and pathogen spread in susceptible and partially resistant tissues of both pot-grown wheat, barley and oat seedlings and field-grown inoculated wheat trials. Further research was conducted to determine whether differences in pathogenicity occur amongst a small subset of Australian Fpg isolates. Seedling experiments confirmed that differences in disease ratings between susceptible and partially resistant genotypes are detected in younger leaf sheaths of older seedlings. At later harvest times differences between these genotypes are not significant in older leaf sheaths. Re-isolation of Fpg from inoculated seedlings has shown that each tissue was infected later in partially resistant genotypes compared to susceptible ones with a significantly lower number of isolations recorded at each harvest time in 42 day old seedlings. Barley cultivars were rapidly infected by the pathogen and exhibited high levels of disease symptoms. By comparison levels of infection in oats were low compared to all other genotypes. No significant differences between genotypes were observed in coleoptile tissues, either in fungal colonisation or development of disease symptoms. Disease development in the subcrown internode varied between lines/cultivars but was not representative of the relative susceptibility of each genotype. The pathogen did not appear to invade plant tissue via the vascular system but rather spread directly across the stem from leaf sheath to leaf sheath. Field trials were designed to study disease symptom development and localisation of Fpg hyphae in all expanded tissues (excluding head and roots) in wheat genotypes of known susceptibility to crown rot. Plants were harvested at approximately fortnightly intervals throughout the growing season. The main effects and interactions of harvest, genotype and tiller on each plant part were examined with a detailed statistical analysis of differences seen in these factors between susceptible and partially resistant wheat genotypes, in two inoculated field trials. While differences between genotypes were mostly not significant at each harvest when disease rating or isolations from leaf sheath tissues were examined, important differences between susceptible and resistant genotypes were seen in disease developments and Fpg infections of stem tissue in field trials. Restriction of pathogen growth and symptom development was more pronounced in the tissues of 2-49 (possesses seedling resistance) than in the field resistant Sunco. At present, the mechanisms that lead to these resistance responses are unknown. The pathogenicity study aimed to determine whether 7 Fpg isolates and a mixed inoculum differed in ability to cause crown rot in 9 wheat genotypes ranging in susceptibility to this disease. Although a genotype*inoculum interaction was significant, there is no evidence of stable pathogenic races in the isolates examined in these experiments. The growth of all isolates was partially inhibited in a consistent manner on resistant genotypes when compared to very susceptible genotypes. These results confirm significant differences in the aggressiveness of Fpg isolates on wheat, evidenced by variation in mean disease severity between isolates growing on a range of host genotypes.

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GREGORI, ROSSELLA. „ROLE OF THE PLANT-PATHOGEN CROSS TALKING IN FUSARIUM MYCOTOX IN PRODUCTION AND MASKING IN MAIZE“. Doctoral thesis, Università Cattolica del Sacro Cuore, 2014. http://hdl.handle.net/10280/2476.

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In this work we investigated the in vivo and in vitro ecological conditions that can favour the fumonisin production, both free and hidden forms, in the maize-Fusarium verticillioides pathosystem. Samples of different maize hybrids have been collected from dough to the harvest maturity to follow the trend of fungal incidence and both fumonisin forms contamination, but also the changes in chemical composition. Differences in the level of contamination have been found among hybrids during the growing season. Furthermore, the production of fumonisins has been found correlated to the total lipids content, another parameter that changed during the growing season. This finding underlined the existence of a relationship between toxin contamination and fatty acids composition of the hybrids. Recently the existence of a cross talk between plant and pathogen has been demonstrated, based on some oxidized signal molecules (oxylipins) produced from fatty acid precursors. This result was also confirmed by the molecular analysis on the in vitro pathosystem that showed differences in the activation of the genes involved in plant and fungal oxylipins production during the incubation time. Also post-harvest contamination of maize was investigated in this study, with particular attention to the effects of the drying treatment, a common post-harvest practice aimed at decreasing the water availability, and to the storage capacity of a new low cost storage system, silo bag. The drying treatment was showed to affect fumonisins content, in particular an increased fumonisins contamination was detected after heat treatments. This increment seemed to be produced by chemical changes of matrix components, caused by high temperature, that produced the release of hidden fumonisin in free form. Silo bags were shown to be an effective system to store cereals because no significant change occurred in fungi or toxins contamination during a 9-month storage. Therefore, being more flexible and less expensive than traditional store houses, they should be very useful for farmers.

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Franke, JanaLynn. „Identification of the Infection Route of a Fusarium Seed Pathogen into Non-Dormant Bromus tectorum Seeds“. BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4318.

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The genus Fusarium has a wide host range and causes many different forms of plant disease. These include seed rot and seedling blight diseases of cultivated plants. The Fusarium-caused diseases of wild plants are less well-known. In this study we examined Fusarium sp. n-caused disease development on non-dormant seeds of the important rangeland weed Bromus tectorum as part of broader studies of the phenomenon of stand failure or ‘die-off’ in this annual grass. We previously isolated an undescribed species in the Fusarium tricinctum species complex from die-off soils and showed that it is pathogenic on seeds. It can cause high mortality of non-dormant B. tectorum seeds, especially under conditions of water stress, but rarely attacks dormant seeds. In this study, we used scanning electron microscopy (SEM) to investigate the mode of attack used by this pathogen. Non-dormant B. tectorum seeds (i.e., florets containing caryopses) were inoculated with isolate Skull C1 macroconidia. Seeds were then exposed to water stress conditions (-1.5MPa) for 7 d, then transferred to free water. Time lapse SEM photographs of healthy vs. infected seeds revealed that hyphae under water stress conditions grew toward and culminated their attack at the abscission layer of the floret attachment scar. A prominent infection cushion, apparent macroscopically as a white tuft of mycelium at the radicle end of the seed, developed within 48 hours after inoculation. Seeds which lacked an infection cushion completed germination upon transfer to free water, whereas seeds with an infection cushion were almost always killed. In addition, hyphae on seeds that did not initiate germination lacked directional growth and did not develop the infection cushion. This strongly suggests that the fungal attack is triggered by seed exudates released through the floret attachment scar at the initiation of germination. Images of cross-sections of infected seeds showed that the fungal hyphae first penetrated the caryposis wall, then entered the embryo, and later ramified throughout the endosperm, completely destroying the seed.

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