Nos travaux de recherches de thèse portent sur une étude comparative entre le déclanchement des mécanismes de défense in planta de la plante de melon après élicitation biotique, et un traitement avec un produit ayant des propriétés de Stimulateur des Défenses Naturelles (SDN). Le pathosystème étudié est Cucumis melo - Fusarium Oxysporum melonis. L'éliciteur abiotique SDN utilisé codé FEN560 est un extrait de graines de fenugrec (Trigonella foenum-graecum). Les principaux travaux sont : 1) L'analyse des activités enzymatiques relatives au stress et caractérisation d'enzymes PR. 2) L'étude des métabolites du métabolisme secondaire, notamment la production l'accumulation des composés organiques volatiles (COV). 3) Une étude de l'expression de gènes candidats impliqués dans la production de ces PR-protéines et/ou dans les voie de signalisation est aussi entreprise ; Les principaux résultats se traduisent par (i) une précocité et intensité de l'induction des activités enzymatiques étudiées pour les deux variétés et pour les organes d'un même plant (ii) Le priming est généralement observé au niveau du site de la seconde élicitation (infection FOM) avec une induction remarquable des PR-protéines. (iii) L'élicitation est Systémique, car l'induction se transmet mais à moindre intensité sur les intervalles de temps étudiés. (iv) L'augmentation de l'émission des COV coïncide avec l'induction de la LOX. Il est aussi noté l'émission de nouvelles molécules connus par leurs propriétés antibiotique ou répulsive des insectes herbivores ou attractive des prédateurs d'insectes herbivores. Les résultats sur les expressions des gènes candidats sont corrélés avec les activités enzymatiques et la production des composés organiques. Il en est ressorti que l'induction de la résistance par le traitement par pulvérisation de FEN560 est similaire au phénomène de « primig » dans la résistance systémique induite. / This work is a comparative study between defense mechanisms in melon plant induced by biotic elicitor and treatment by plant extract having simulative proprieties of plant defense mechanisms. The studied pathosystème is Cucumis melo - Fusarium oxysporum fsp melonis. The used plant extract elicitor is named FEN560, it is from fenugreek seeds (Trigonella foenum-graecum). The main works were: 1) Analysis of the enzymatic activities relating to the stress and characterization of PR-proteins sch as peroxidases and chitinases. The lipoxygenase (LOX), the key enzyme of oxylipins biosynthesis and phenylalanine ammonia-lyase, the key enzyme of the phenylpropanoids pathway, were also studyed. 2) The study of the metabolites of the secondary metabolism, in particular accumulation of volatile organic compounds (VOC). 3) A study of expression candidate genes implied in the production of Pr-proteins and the induced resistance pathways is also undertaken. The main results: (i) precocity and intensity of enzymatic activities induction for the two varieties after inoculation of pretreated plants (ii) the priming is generally observed in the site of the second elicitation with a remarkable induction of PR-proteins. (iii) The elicitation induced by FEN560 is systemic; because induction is transmitted between roots and shoots (iv) The modification of VOC emissions coincides with the induction of the LOX activity. It is also noticed the emission of new molecules known for their antibiotic properties or repulsive of the insects herbivorous or attractive of predatory of herbivorous insects. The results on the genes candidates' expression are in general correlated with the enzymatic activities and the production of the volatile organic compounds through LOX activity. In brief, the induction of resistance by the treatment by FEN560 is similar to the phenomenon of "primig" in induced systemic resistance.

Dans ce travail, nous avons étudié la contribution que les inhibiteurs de glicosidases ont dans la réponse de défense du blé à Fusarium graminearum. Nous avons démontré que les inhibiteurs de xylanases ont la capacité à la fois de contenir l'activité de dégradation de xylanases sécrétées par l'agent pathogène, et de limiter la possibilité de provoquer nécrose dans les tissus du blé. Nous avons démontré que l’expression de la PvPGIP2 dans la lemme, la paléa, les anthères et le rachis détermine une réduction des symptômes de la fusariose de l’épi, au même niveau de l’expression constitutive de cet inhibiteur. Inversement, l'expression de la PvPGIP2 dans l'endosperme ne détermine pas une réduction des symptômes de la maladie. Cela indique que, lorsque l'agent pathogène a atteint ce tissu, l'activité de polygalacturonases de l'agent pathogène n’est pas indispensable pour la propagation fongique. Enfin, la combinaison des différents inhibiteurs de glicosidases, qui renforcent différentes parties de la paroi cellulaire dans le même génotype, a été efficace pour réduire les symptômes de la fusariose, par rapport aux génotypes qui présentent seulment un type d’inhibiteur. Nous avons démontré cet aspect à travers les plantes qui expriment la PvPGIP2 et le TAXI-III. Au contraire, les génotypes qui expriment la PvPGIP2 et l’AcPMEI n’ont pas montré un effect additif sur la résistance, probablement parce que ils renforcent la même partie de la paroi cellulaire, c’est-à-dire la pectine. / In this work we studied the contribution of glycosidase inhibitors in the defense response of wheat against Fusarium graminearum. We demonstrated that xylanase inhibitors are able to limit both the degrading activity of the xylanases secreted by the pathogen and to limit their ability to induce necrosis in wheat cell suspensions and tissues.We demonstrated that the expression of PvPGIP2 in lemma, palea, anthers and rachis causes a reduction in Fusarium head blight symptoms, at the same level of the constitutive expression of this inhibitor. On the contrary, the expression of PvPGIP2 in the endosperm did not result in a reduction of disease symptoms, suggesting that once the pathogen has reached the endosperm, the activity of polygalacturonases secreted by the pathogen is not essential for the progression of symptoms.The pyramiding of glycosidase inhibitors in the same genotype is effective in reducing FHB symptoms although it depends on the specific combination. Pyramiding of PvPGIP2 and AcPMEI does not enhance further wheat resistance against FHB, possibly because they target the same virulent component secreted by the pathogen, that is PG. Conversely, the pyramiding PvPGIP2 and TAXI-III supports a further improvement of resistance compared to plants carrying only PvPGIP2 or TAXI-III.

Fusarium oxysporum f.sp. cubense Schlecht (Foc), causal agent of Fusarium wilt of banana (Panama disease), is considered to be one of the most serious threats to banana production in the world. There is no effective control measure for Fusarium wilt, except for the replacement of susceptible with resistant banana varieties. However, resistant varieties are not always acceptable to producers and local consumer markets. A greater awareness of the detrimental effect of chemicals on the environment has stimulated research on biological control of plant pathogens. The use of indigenous microorganims, such as non-pathogenic F. oxysporum and the bacterium Pseudomonas fluorescens, therefore, offers not only an environmentally safe but also an economical approach to combat Fusarium wilt of banana as part of an integrated disease management strategy. Non-pathogenic F. oxysporum and P. fluorescens isolates have previously been isolated from the root rhizosphere in disease suppressive soils. These isolates have the ability to reduce the incidence of Fusarium wilt in greenhouse pathogenicity trials. In this study we had hoped to expand on existing knowledge on the biological control of Fusarium wilt of banana with non-pathogenic endophytic F. oxysporum and P. fluorescens. Isolates that significantly suppress disease development in greenhouse trials were tested under field conditions. Physiological and histological studies were also performed to understand the modes of action of putative biological control agents. For the histological investigations, non-pathogenic F. oxysporum isolates were modified with green and red fluorescent proteins. Chapter 1 depicts a general overview of the biological control of Fusarium wilt diseases of agricultural crops. This chapter addresses the biology and pathogenesis of F. oxysporum, before strategies to control Fusarium wilt are discussed. The application of biological control organisms was analysed in terms of potentially useful organisms, where they can be isolated, and their possible modes of action. Finally, factors that influence biological control of Fusarium wilt diseases are discussed. A good source of prospective biocontrol agents is suppressive soils. In Chapter 2, non-pathogenic F. oxysporum isolates were collected from healthy banana roots in disease suppressive soil. Random Fragment Length Polymorphisms of the intergenic spacer region were then applied to group the non-pathogenic F. oxysporum isolates into genotypes, from which candidates were selected for biological control studies. The selected endophytes were then inoculated onto banana roots to determine their ability to act as biocontrol agents against Foc. The isolates that protected banana best against Fusarium wilt in the greenhouse, together with P. fluorescens WCS 417, were tested in the field to determine whether these isolates could effectively reduce disease incidence in an uncontrolled environment. The ability of non-pathogenic F. oxysporum and P. fluorescens WCS 417 to induce systemic resistance in Cavendish banana plants against Foc was investigated in Chapter 3 with the use of a split-root technique. The putative biocontrol agents were inoculated, separately and in combination, on one half of the roots in a split-root experiment, while the other half was challenged by a pathogenic isolate of Foc. Five different phenolic acids were assayed which included total soluble phenolic acids, non-conjugated (free acids) phenolic acids, ester-bound phenolic acids, glycosidebound phenolic acids and cell wall-bound phenolic acids. The knowledge gained will contribute to the understanding of how the biocontrol agents may induce defense responses in banana roots against Foc. Non-pathogenic isolates of F. oxysporum were transformed with the green fluorescent protein (GFP) and DsRed-Express genes in Chapter 4. These isolates were used to visualise their interactions with a GFP-transformed Foc isolate on the banana root in a non-destructive manner by means of confocal laser scanning microscopy (CLSM) in Chapter 5. The ability of non-pathogenic F. oxysporum and P. fluorescens WCS 417 to induce structural changes was also investigated with a split-root system using the CLSM. Antibioses as a mode of action of the two potential biocontrol agents was tested in vitro. Understanding the modes of action of non-pathogenic F. oxysporum and P. fluorescens WCS 417 are important when considering strategies for the implementation of these isolates in an integrated disease management strategy against Fusarium wilt of banana. / Dissertation (MSc (Plant Pathology))--University of Pretoria, 2011. / Microbiology and Plant Pathology / unrestricted

A incidência de ceratite infecciosa relacionada a lentes de contato ocasionada por espécies de Acanthamoeba e Fusarium tem aumentado nos últimos anos. Esses organimos compartilham vários ambientes e casos de coinfecção foram relatados. Interações entre amebas e outros micro-organismos podem resultar em mudanças significativas para ambos, como o aumento da virulência em hospedeiros mamíferos. Neste estudo, foi avaliada a interação das cepas Neff, T4 e T4 pulmão de Acanthamoeba castellanii com Fusarium solani, bem como as possíveis implicações no desenvolvimento de ceratite. A. castellanii foi capaz de fagocitar F. solani e os conídios foram capazes de germinar dentro da ameba. A cocultura com ameba viva, bem como o sobrenadante da cultura e o lisado amebiano aumentaram significativamente o crescimento do fungo. Além disso, F. solani vivo e o seu sobrenadante de cultura aumentaram a sobrevivência da ameba, mas de forma diferente em cada cepa amebiana. A presença do fungo resultou em aumento de encistamento das cepas amebianas T4 pulmão e T4, bem como aumentou a resistência da cepa Neff à clorexidina. Curiosamente, a passagem pela ameba aumentou o efeito citopático de F. solani em células de mamíferos. Esses resultados mostram que A. castellanii e F. solani têm uma relação de protocooperação, com benefícios para ambos, e especialmente, indicam um possível efeito sobre as características de virulência de ambos os organismos. Assim a interação entre A. castellanii e F. solani pode resultar em impactos graves nos casos de ceratite. / The incidence of Acanthamoeba and Fusarium species has increased in contact lens-related infectious keratitis. They share several environments and cases of co-infection have been reported. The interaction between the amoeba and other microorganisms may result in significant changes for both, like increased virulence in mammalian hosts. In this study, we evaluated the interaction of Neff, T4 and T4 lung strains of Acanthamoeba castellanii with Fusarium solani and the implications in keratitis. A. castellanii phagocyted the fungi, and conidia were able to germinate inside the amoeba. The co-culture with live amoeba as well as the amebic culture supernatant and lysate significantly increased fungal growth. Moreover, live F. solani and the its culture supernatant enhanced the survival of amoeba, but differently in each A. castellanii strain. The presence of fungi resulted in increased amoebal encystment of T4 and T4 lung strains, end increased the resistence of Neff strain to chlorhexidine. The encystment of T4 and T4 lung strains was increased by the fungi. Interestingly, the passage by Neff amoeba increased the cytophatic effect of F. solani on mammalian cells linage. These results show that A. castellanii and F. solani have a protocooperation relationship, with benefits for both, and especially indicate a possible effect on virulence characteristics of both organisms. These data suggest that the A. castellanii-F. solani interaction may cause severe impacts in keratitis.

Orientadores: Maria Luiza Moretti, Angélica Zaninelli Schreiber / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-27T08:47:24Z (GMT). No. of bitstreams: 1 Moraes_JoseRenatode_M.pdf: 2487255 bytes, checksum: 4c5a21c13a0b57cf864dbf79cca990fd (MD5) Previous issue date: 2014 / Resumo: Introdução: os fungos do gênero Fusarium são ubíquos no meio ambiente e causam doenças em plantas e aos seres humanos. Objetivos: 1)estabelecer o protocolo para a coleta e o isolamento de Fusarium spp. no ar; 2)isolar fungos do gênero Fusarium do ar da enfermaria de Hematologia e da Unidade de Transplante de Medula Óssea (TMO) no Hospital de Clínicas (HC) da Universidade Estadual de Campinas (UNICAMP) e comparar a relação genética de isolados ambientais de Fusarium spp. com os isolados a partir de hemoculturas de rotina diagnóstica de pacientes hospitalizados durante os anos de 2002 a 2013, 3)identificar os fungos do gênero Fusarium ao nível de complexo de espécies por PCR em tempo real, e ao nível de espécie pelo sequenciamento de fragmento do gene EF1?. Metodologia: foram colhidas amostras de ar nas unidades de TMO (que possui controle de ar através de filtros HEPA e fluxo de ar de pressão positiva) e na Hematologia (unidade sem controle do ar) do HC. De 2006 a 2013 foram identificados 18 isolados de Fusarium spp. em culturas de sangue. A coleta de ar foi realizada através do amostrador de ar BioSamp modelo MBS 1000D (YotsubishiCorp Japão). Um meio de cultura seletivo para Fusarium (Agar Komada com modificações) foi usado na placa de Petri dentro do amostrador de ar. O volume de ar de 1000 mL e 500 mL foram aspirados da Hematologia e enfermarias de TMO, respectivamente. Após o tempo de incubação, as colônias que cresceram nas placas foram avaliadas macroscopicamente e microscopicamente para identificação morfológica. Fusarium spp. foram identificados através de um novo ensaio de PCR em tempo real composto por dois ensaios de PCR em tempo real: um específico para o gênero Fusarium e um ensaio específico para detecção específica do complexo de espécies de Fusarium solani (FSSC). Para confirmar o complexo de espécies de Fusarium, uma região parcial do gene EF-1? foi sequenciado. O alinhamento das sequências foi realizado no programa Clustal W e a análise filogenética utilizou o programa Mega5 com o algorítimo Neighbor-Joininge Bootstrap de 1000 replicatas. Resultado: foram isoladas 108 cepas de Fusarium spp. destes 28% na unidade de TMO e 78% na Hematologia. Os complexos de espécies encontrados foram: 10% FCSC, 21% FIESC, 1% FOSC, 12% FSSC, 51% GFSC e 5% não definido. Na TMO a maior prevalência foi da espécie Fusarium solani (9/30 isolados) e na Hematologia Fusarium verticillioides (25/31 isolados). Não foi possível constatar relevância entre a temperatura e umidade do ar em relação ao aumento ou diminuição de isolados nas coletas. Nove isolados FSSC do ar e 8 de sangue apresentaram BT 99%. Conclusão. Os dados de análise filogenética sugeriram que os isolados de sangue de pacientes e ambientais foram similares sugerindo que o ambiente pôde representar uma fonte potencial de infecção para os pacientes imunodeprimidos / Abstract: Introduction:the fungus Fusarium are ubiquitous in the environment and cause diseases in plants and humans. Objectives: isolate fungi Fusarium in the air of the ward Hematology and Unit of Bone Marrow Transplantation (BMT) at the Hospital de Clinicas (HC), State University of Campinas (UNICAMP), compare the phylogenetic relationship of environmental isolates of Fusarium spp .with isolates from blood cultures of routine diagnosis of hospitalized patients during the years 2002-2013, to establish protocol for the collection and isolation of Fusarium spp. in the air, identify the fungi Fusarium species complex level by real time PCR, and to species level by sequencing the fragment EF1 ? gene. Methodology: air sample was collected in BMT units (which has control of air through HEPA filters and air flow positive pressure) and Hematology (there is not self control air inlet) HC. From 2006 to 2013, 18 samples obtained from blood cultures with the presence of Fusarium spp. were added to study the relationship between degree of molecular clinical isolates isolated from the air. The air sampling was performed using the Bio air sampler Samp MBS model 1000D (Yotsubishi Corp. Japan). A selective medium for Fusarium (Komada Agar changes by Y. Mikami, Chiba University) was used in the petri dish in the air sampler. The air volume of 1000 mL and 500 mL were aspirated Hematology and BMT wards, respectively. After the incubation time, colonies that grew on the plates were evaluated macroscopically and microscopically for morphological identification. Fusarium spp. were identified by PCR of a new system in real time according to Muraosa et al. comprising two PCR assays in real time: the specific assay Fusarium and a specific assay for specific detection of Fusarium solani (FSSC) complex. To confirm the complex of Fusarium species, a partial region of the EF-1? gene was sequenced. The alignment of sequences was performed in Clustal W program and phylogenetic analysis used Mega5 program with the neighbor-joining algorithm and bootstrap 1000 replicates. Results: 108 ceepas Fusarium spp were isolated. 28% of these isolates form the BMT unit and 78% in Hematology. Overall the species complexes ficarm divided as follows: 10% FCSC, 21% FIESC 1% FOSC, FSSC 12%, 51% and 5% GFSC nd not defined). In the BMT was higher prevalence of the species Fusariu solani (9/30 isolates) and the Hematology espéciecom largest presence is Fusarium verticillioides (25/31 isolates). Unable to find relevance between temperature and air humidity in relation to the increase or decrease in collections of isolates. Nine isolates of Fusarium solani air obtained from the same source ancestras 8 Fusarium solani isolates from blood (BT 99%). Conclusion:Fusarium spp were isolated in 108 environmental samples en all evaluated environments. Phylogenetically findings suggest equivalence between environmental isolates and isolates from the blood of patients. The collection protocol set showed satisfactory for the specific isolation of Fusarium result. The findings of Fusarium were grouped into complexes FSSC and FSSC not the technique of real-time PCR and sequencing of the gene EF1? allowed to classify the isolates in the species level / Mestrado / Clinica Medica / Mestre em Ciências

As condições climáticas presentes nas regiões produtoras de trigo, do Brasil e dos principais países do qual o produto é importado, favorecem o aparecimento de doenças importantes desta cultura, dentre elas a fusariose, causada principalmente pelo fungo Fusarium graminearum Schwabe. Além dos danos diretos causados pela doença, os grãos infectados podem ser tóxicos para o homem e animais devido à presença de micotoxinas especialmente o desoxinivalenol (DON). Um total de 100 amostras de trigo, sendo 50 de trigo nacional (provenientes do Estado de São Paulo, Paraná e Rio grande do Sul) e 50 de trigo importado (Argentina e Paraguai) foram coletadas de empresas que normalmente comercializam ou processam trigo durante o período de maio a dezembro de 2005. Foram avaliados o percentual de freqüência de fungos, especialmente Fusarium graminearum, a contaminação com DON, percentual de grãos giberelados e realizadas correlações entre os parâmetros avaliados. Os resultados indicaram que freqüência média de Fusarium graminearum e F. spp. foram baixas (&#8804;2,6 e &#8804;3,6%, respectivamente), porém foi maior no trigo nacional do que no trigo importado. Do total de amostras avaliadas 94% do trigo nacional e 88% do trigo importado apresentaram-se contaminadas com DON em níveis médios de 332 µg.kg-1 (nacional) e 90 µg.kg-1 (importado). Existiu correlação positiva e significativa entre contaminação com DON e percentual de grãos giberelados (r = 0,83; p<0,0001), freqüência de Fusarium graminearum (r = 0,92; p<0,0001) e freqüência de Fusarium spp. (r = 0,86; p<0,0001). / The climatic conditions present in wheat producing areas from Brazil and main countries from which the product is imported favor the occurrence of important diseases in this crop, among them the Fusarium Head Blight or scab. It is mainly caused by the fungus Fusarium graminearum Besides, direct damages caused by this disease, the infected kernels may be toxic for humans and animals due to presence of mycotoxins (e.g deoxynivalenol). A total of 100 wheat samples, being 50 from national production (São Paulo, Paraná and Rio Grande Do Sul states) and 50 from imported one (Argentina and Paraguay), were collected during the period of May to December 2005 from companies that normally commercialize or process wheat. Frequency (%) of fungi occurrence, specially Fusarium graminearum and Fusarium spp., DON contamination and Fusarium damaged kernels (%) were evaluated. Correlations between the evaluated parameters were carried out. Frequency of Fusarium graminearum and Fusarium spp. were low (&#8804;2.6 and &#8804;3.6%, respectively), however it was higher in Brazilian wheat when compared with imported wheat. Ninety-four percent of national wheat samples and 88% of the imported samples were DON contaminated (mean levels, 332 µg.kg-1 and 90 µg.kg-1, respectively). The occurrence of DON was highly correlated with percentage of Fusarium damaged kernels, (r = 0,83; p<0.0001), percentual frequency of Fusarium graminearum (r = 0,92; p<0,0001) and percentual frequency of Fusarium spp. (r = 0,86; p<0,0001).

A castanha-do-brasil é uma planta de grande importância econômica na região da Amazônia. Os baixos níveis tecnológicos característicos de sua cadeia produtiva e as condições inadequadas de manejo da matéria prima, favorecem o aparecimento de contaminação por fungos produtores de micotoxinas. A fumonisinas B2 (FB2) é uma micotoxina produzida por espécies de Fusarium e Aspergillus section Nigri, e é motivo de preocupação para a saúde humana e de animais. O objetivo do presente trabalho foi verificar o potêncial toxigênico quanto à produção de fumonisina B2 das cepas de A. section Nigri isolados de castanha-do-brasil e verificar a contaminação desse alimento por essa micotoxina. De um total de 200 cepas de A. section Nigri testadas quanto à capacidade de produção de fumonisina B2, apenas 39 cepas (19,5 %) produziram FB2, cento e trinta e oito (69 %) não foram produtoras de fumonisina B2 e 23 cepas (11,5 %) apresentaram picos menores que o limite de detecção. Das 100 amostras de castanha-do-brasil analisadas, nenhuma estava contaminada por fumonisina B2. / Brazil nut is a plant with vast economic importance in the Amazon region and is an important product exported by Brazil. However, low levels of technology, and inadequate management of raw material favor the appearance of contamination by fungi that produce toxic metabolites called mycotoxins. Fumonisin B2 (FB2) is a mycotoxin produced by Fusarium species and Aspergillus section Nigri, and is of concern for human health. The aim of this study was to assess the toxigenic potential for fumonisin B2 production by Aspergillus section Nigri strain isolated from brazil nut and check the contamination of food by this mycotoxin. From a total of 200 strains of Aspergillus section Nigri tested for the ability to produce fumonisin B2, only 39 strains (19.5 %) were producing FB2, 138 (69 %) were not producing fumonisin B2, and 23 strains (11.5 %) showed peaks less than the detection limit. Of the 100 samples of brazil nuts analyzed, none were contaminated with fumonisin B2.

No description available.

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.

Fusarium head blight (FHB), caused by Fusarium graminearum, is a serious disease of wheat and barley that has caused several billion dollars in crop losses over the last decade in the United States. Spores of F. graminearum are released from corn and small grain residues left-over from the previous growing season and are transported long distances in the atmosphere before being deposited.  Current risk assessment tools consider environmental conditions favorable for disease development, but do not include spore transport. Long distance transport models have been proposed for a number of plant pathogens, but many of these models have not been experimentally validated. In order to predict the atmospheric transport of F. graminearum, the potential source strength (Qpot) of inoculum must be known.  We conducted a series of laboratory and field experiments to estimate Qpot from a field-scale source of inoculum of F. graminearum.  Perithecia were generated on artificial (carrot agar) and natural (corn stalk) substrates.  Artificial substrate (carrot agar) produced 15±0.4 perithecia cm-2, and natural substrate (corn stalk) produced 44±2 perithecia cm-2.  Individual perithecia were excised from both substrate types and allowed to release ascospores every 24 hours.  Perithecia generated from artificial (carrot agar) and natural (corn stalk) substrates released a mean of 104±5 and 276±16 ascospores, respectively.  A volumetric spore trap was placed inside a 3,716 m2 clonal source of inoculum in 2011 and 2012.  Results indicated that ascospores were released under field conditions predominantly (>90%) during the night (1900 to 0700 hours).  Estimates of Qpot for our field-scale sources of inoculum were approximately 4 billion ascospores per 3,716 m2.  Release-recapture studies were conducted from a clonal field-scale source of F. graminearum in 2011 and 2012. Microsatellites were used to identify the released clone of F. graminearum at distances up to 1 km from the source. Dispersal kernels for field observations were compared to results predicted by a Gaussian dispersal-based spore transport model.  In 2011 and 2012, dispersal kernel shape coefficients were similar for both results observed in the field and predicted by the model, with both being dictated by a power law function, indicating that turbulence was the dominant transport factor on the scale we studied (~ 1 km).  Model predictions had a stronger correlation with the number of spores being released when using a time varying q0 emission rate (r= 0.92 in 2011 and r= 0.84 in 2012) than an identical daily pattern q0 emission rate (r= 0.35 in 2011 and r= 0.32 in 2012).  The actual numbers of spores deposited were 3 and 2000 times lower than predicted if Qpot were equal to the actual number of spores released in 2011 and 2012, respectively. Future work should address estimating the actual number of spore released from an inoculated field during any given season, to improve prediction accuracy of the model.  This work should assist in improving current risk assessment tools for FHB and contribute to the development of early warning systems for the spread of F. graminearum. / Ph. D.