Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2018-06-13T12:06:52Z No. of bitstreams: 1 texto completo.pdf: 907973 bytes, checksum: 02a626fc75495ec20f6054c31c8939c7 (MD5) / Made available in DSpace on 2018-06-13T12:06:52Z (GMT). No. of bitstreams: 1 texto completo.pdf: 907973 bytes, checksum: 02a626fc75495ec20f6054c31c8939c7 (MD5) Previous issue date: 2018-02-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Um dos fatores limitantes na produção da soja é o fungo Sclerotinia sclerotiorum, causador da podridão branca da haste (PBH). A produtividade é comprometida quando há condições de temperaturas entre 18 e 22 Co e umidade relativa acima de 80%. Ainda não é conhecido genótipo imune à S. sclerotiorum. Contudo, muitos estudos em casa de vegetação com o método de inoculação straw test tem sido feitos para seleção de genótipos com resistência fisiológica ao fungo. A associação genômica ampla (GWAS) vem facilitando a detecção de genes e QTLs (Quantitative Trait Loci) responsáveis por características agronômicas, por meio da utilização de marcadores SNPs (single nucleotide polymorphism). Nosso objetivo foi realizar GWAS em 146 cultivares brasileiras e identificar SNPs, QTLs e genes relacionados com a resistência fisiológica à PBH em soja. Foram obtidos notas e o comprimento de lesão aos 3, 7, 10 e 14 dias após inoculação (DAI). Com a progressão da doença obtida a partir da diferença entre os dias de avaliação de comprimento de lesão e com as notas, pôde-se observar 25 e 10 SNPs significativos em 2016 e 2017, respectivamente, distribuídos em 14 cromossomos diferentes. Houve 6 SNPs localizados em QTLs já descritos. Haplótipos baseados nos marcadores significativos confirmaram a baixa contribuição dos SNPs quando analisados separadamente para resistência fisiológica à PBH. Com base nos SNPs detectados neste estudo, foram confirmados 67 genes candidatos em 2016 e 23 genes candidatos em 2017 para resistência a doenças. Esses resultados reforçam o fato de que esta é uma característica complexa, relacionada com muitos genes. Os resultados ainda sugerem que sob diferentes condições ambientais o patógeno é capaz de suprimir genes da soja, aumentando a susceptibilidade da cultura ao fungo. No entanto, ainda são necessários estudos de validação dos SNPs encontrados para utilização em seleção assistida e programas de melhoramento no futuro. / One of the limiting factors on soybean production is the White Mold (WM), caused by fungus Sclerotinia sclerotiorum. Yield is compromised when conditions are temperature between 18 and 22 Co and relative humidity above 80%. Moreover, immune genotype is unknow to S. sclerotiorum. However, many greenhouses studies using the straw test method have been done to select genotypes with physiological resistance to the fungus. Genome wide association studies (GWAS) has been making it easier to detect genes and QTLs (Quantitative Trait Loci) responsible for agronomic traits, by using SNPs (single nucleotide polymorphism) markers. Our objective was to do GWAS in 146 Brazilians cultivars and to identify SNPs, QTLs and genes associated with WM physiological resistance in soybean. Notes and lesion length were obtained at 3, 7, 10 and 14 days after inoculation (DAI). With the disease progression obtained from the difference between the days of evaluation of lesion length and with the notes, it can be observed 25 and 10 significant SNPs in 2016 and 2017, respectively, distributed in 14 different chromosomes. There were 6 SNPs located in QTLs already described. Haplotypes based on significant markers have confirmed the low contribution of SNPs when analyzed separately for physiological resistance to WM. Based on detected SNPs in this study, 67 candidate genes in 2016 and 23 candidate genes in 2017 were confirmed for resistance to diseases. These results reinforce the fact that physiological resistance to WM is a complex trait, associated with many genes. The results still suggest that in different conditions the pathogen is capable of suppressing soybean genes, increasing the susceptibility of the crop to the fungus. However, more studies are necessary for validation of SNPs found for use in assisted selection and breeding programs in the future.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2015-11-05T15:38:29Z No. of bitstreams: 1 texto completo.pdf: 489618 bytes, checksum: 7609724ea0ef2f3496bf38ea80688185 (MD5) / Made available in DSpace on 2015-11-05T15:38:29Z (GMT). No. of bitstreams: 1 texto completo.pdf: 489618 bytes, checksum: 7609724ea0ef2f3496bf38ea80688185 (MD5) Previous issue date: 2015-07-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / O mofo-branco (MB), causado pelo fungo Sclerotinia sclerotiorum, é doença séria em lavouras irrigadas de feijão. O uso de cultivares com resistência parcial ao MB faz parte do manejo da doença, e pode reduzir aplicações de fungicida para seu controle. Avaliou-se a possibilidade de se reduzir as aplicações de fungicida em genótipo com resistência parcial ao MB. Ensaios foram conduzidos em três municípios (Coimbra, Viçosa e Oratórios) da Zona da Mata de Minas Gerais, no outono-inverno, com irrigação por aspersão, em área com histórico de MB. Os tratamentos foram dispostos no arranjo fatorial 3 x 4: genótipos (VC 17, Pérola ou BRSMG Madrepérola) e aplicações de fungicida (0, 1, 2 ou 3). A linhagem VC 17 está entre os genótipos com maior resistência de campo ao MB. A cultivar Pérola apresenta resistência moderada e a cultivar BRSMG Madrepérola é suscetível. O fungicida fluazinam (0,625 L/ha) foi aplicado na floração e repetido entre 7 e 10 dias depois. Foi usado o delineamento em blocos ao acaso, com quatro repetições. Em média, a intensidade (incidência + severidade) do MB variou de baixa (Coimbra) a moderada/alta (Oratórios); e a produtividade de grãos, de 2638 a 3556 kg/ha. Em Viçosa e Oratórios a pressão da antracnose foi alta, e esse foi um dos fatores responsáveis pela menor produtividade dos genótipos Pérola e VC 17, em relação à cultivar BRSMG Madrepérola. Em Viçosa, o VC 17 exibiu menos sintomas de MB que as cultivares Pérola e BRSMG Madrepérola. Em Coimbra e Oratórios, os sintomas de MB nos genótipos VC 17 e Pérola foram semelhantes, mas, em geral, esses genótipos foram menos prejudicados por essa doença que a cultivar BRSMG Madrepérola. Em Oratórios, houve significativa redução dos sintomas de MB com duas aplicações do fungicida, independente do genótipo, enquanto em Coimbra só a BRSMG Madrepérola teve redução do MB, com uma aplicação do fungicida. Em Viçosa, a cultivar BRSMG Madrepérola teve redução da doença com até duas aplicações do fluazinam, enquanto a cultivar Pérola apresentou redução do MB com uma aplicação. Nesse município, o VC 17 não teve redução do MB com o uso de fungicida. Portanto, os resultados de Coimbra, em que houve baixa pressão de MB, e de Viçosa (baixa/moderada intensidade de MB) sustentam, parcialmente, a nossa hipótese de que genótipos com alta resistência parcial ao MB necessitam de menor número de aplicações de fungicida em relação a genótipos com baixa resistência parcial. Entretanto, os resultados obtidos em Oratórios, onde a intensidade do MB foi moderada/alta não sustentam nossa hipótese. Os efeitos da antracnose, além dos efeitos do MB, influenciaram a produtividade, o que comprometeu, em parte, o nosso estudo. Logo, estudos adicionais, com bom controle de doenças foliares, sobretudo com alta pressão do MB, são necessários para testar com maior precisão essa hipótese. / White mold (WM), caused by the fungus Sclerotinia sclerotiorum, is a serious disease in irrigated bean crops. The use of cultivars with partial resistance to WM is part of disease management, and can reduce fungicide applications for its control. We evaluated the possibility of reducing fungicide applications in genotype with partial resistance to WM. Trials were conducted in three districts (Coimbra, Viçosa and Oratórios) of Zona da Mata region, State of Minas Gerais, in the fall-winter, with sprinkler irrigation in an area with a history of WM. The treatments were arranged in factorial 3 x 4: genotypes (VC 17 Pérola or BRSMG Madrepérola) and fungicide applications (0, 1, 2 or 3). The line VC 17 is among the genotypes with higher field resistance to WM. The cultivar Pérola has intermediate resistance and the cultivar BRSMG Madrepérola is susceptible. The fungicide fluazinam (0.625 L/ ha) was applied in the flowering and repeated between 7 and 10 days after. A randomized block design with four replications was used. On average the intensity (severity + incidence) of WM ranged from low (Coimbra) to moderate/high (Oratórios); and grain yield, from 2638 to 3556 kg/ha. In Viçosa and Oratórios, the pressure of anthracnose was high, and this was one of the factors responsible for the lower yield of the genotypes Pérola and VC 17, in relation to the cultivar BRSMG Madrepérola. In Viçosa, the line VC 17 showed fewer symptoms of WM than the cultivars Pérola and BRSMG Madrepérola. In Coimbra and Oratórios, the symptoms of WM in the genotypes VC 17 and Pérola were similar, but in general these genotypes were less affected by this disease than the cultivar BRSMG Madrepérola. In Oratórios, symptoms of WM reduced significantly with two fungicide applications, regardless of the genotype, while in Coimbra only BRSMG Madrepérola has a reduction of WM with one fungicide application. In Viçosa, the cultivar BRSMG Madrepérola had reduction of disease with up to two fluazinam applications, while the cultivarPérola had reduction of WM with one application. In this district, the line VC 17 had no reduction of WM with fungicide. Therefore, the results of Coimbra, where there was low pressure of WM, and Viçosa (low/moderate intensity of WM) support, in part, our hypothesis that genotypes with high partial resistance to WM require fewer fungicide applications compared to genotypes with low partial resistance. However, the results obtained in Oratórios, where the intensity of WM was moderate/high did not support our hypothesis. The effects of anthracnose, besides the effects of WM affected yield, which compromised, in part, our study. Thus, additional studies with good control of foliar diseases, especially with high pressure of WM, are required to test this hypothesis with higher accuracy.

This dissertation contains three research chapters conducted on Sclerotinia stem rot (SSR) of canola (Brassica napus L.). This disease is caused by the fungus Sclerotinia sclerotiorum and is considered endemic in canola-producing areas of North Dakota. The first research chapter presents results of a study that evaluated the role of eight phenotyping scoring systems and nine variant calling and filtering methods in detection of QTL associated with response to SSR. The study, conducted on two doubled-haploid mapping populations, showed that using multiple phenotypic data sets derived from lesion length and plant mortality and imputing missing genotypic data increased the number of QTL detected without negatively affecting the effect (R2) of QTL. Nineteen QTL were detected on chromosomes A02, A07, A09, C01, and C03 in this study. The second research chapter presents results of a work that assessed the role of temperature regimes and wetness duration on S. sclerotiorum ascospore germination and ascosporic infection efficiency. This study showed that optimum ascospore germination occurred at 21 °C while it significantly decreased at 10 and 30 °C. Infection efficacy experiments indicated that extreme temperatures and interrupting wet periods were detrimental for the disease development. A logistic regression model with 75% accuracy was developed for the disease perdition. The third research chapter presents results of a study that evaluated the role of temperature on mycelial growth of 19 S. sclerotiorum isolates collected from different geographical regions and on SSR development on plant introduction (PI) lines with different levels of resistance. Mycelial growth and disease development peaked at 25 °C. While lesion expansion on resistant cultivars and the susceptible check was negatively affected at 30 °C, the disease developed significantly on the PI with a high level of susceptibility. Results of these studies provide insights into integrated management strategies of SSR.

No description available.

No description available.

Cette étude vise à mettre en évidence, à l'aide de méthodes d'inoculation dirigée, des différences de résistance à l'infection par le Sclerotinia sclerotiorum entre des lignées de soja disponibles au Québec. Pour ce faire, les objectifs suivants ont été fixés: 1) préciser la résistance ou la sensibilité à la sclérotiniose chez 30 lignées ou cultivars de soja adaptés au Québec; 2) examiner la contribution de la fleur (pétales ou axe floral) et de la tige (intacte ou blessée) à la réaction des lignées ou cultivars; 3) examiner l'efficacité ou la complémentarité de techniques d'inoculation caulinaire ou florale, avec du mycélium ou des ascospores, au champ ou en serre, comme méthodes d'étude de la réaction de lignées de soja au S. sclerotiorum. Les expériences ont été menées à l'Université Laval. En 1998, le mycélium a été utilisé dans trois techniques d'inoculation: inoculation des tiges blessées en serre et au champ, des tiges intactes au champ et des fleurs au champ. Les ascospores collectées de sclérotes produits et conditionnés au laboratoire ont été utilisées à l'hiver 1999 dans une technique d'inoculation des fleurs en serre. L'inoculation de tiges blessées, en serre, a permis de distinguer 12 lignées significativement moins sensibles à la colonisation de la tige blessée que le cultivar Nattosan, le plus sensible. L'inoculation d'ascospores en suspension, en serre, met en évidence deux cultivars significativement moins sensibles à l'invasion des inflorescences (Maple Donovan et Frisquet). Cette recherche montre des différences significatives de résistance à la sclérotiniose chez des lignées de soja du Québec. On précise également, grâce aux inoculations dirigées, la nature de la résistance ou de la sensibilité de quelques lignées: florale (ex: Maple Donovan et Frisquet) ou caulinaire (ex: Nattosan). Ces inoculations dirigées ont présenté une forte variabilité mais elles sont suffisamment discriminantes et complémentaires pour opérer une première sélection de parents partiellement résistants utiles à un programme d'amélioration génétique de la résistance des lignées de soja du Québec au S. sclerotiorum.

No description available.

The biological control agent Pseudomonas chlororaphis PA23 is effective at protecting Brassica napus (canola) from the necrotrophic fungus Sclerotinia sclerotiorum via direct antagonism. Despite the growing importance of biocontrol bacteria in protecting crop plants from fungal pathogens, little is known about how the host plant responds to bacterial priming on the leaf surface and certainly nothing about global changes in gene activity in the presence and absence of S. sclerotiorum. PA23 priming of mature canola plants reduced the number of lesion-forming petals by 90%. Global RNA sequencing of canola tissue at the host-pathogen interface showed a 16-fold reduction in the number of genes uniquely upregulated in response to S. sclerotiorum when pretreated with PA23. Upstream defense-related gene patterns suggest MAMP-triggered immunity via surface receptors detecting PA23 flagellin and peptidoglycans. Although systemic acquired resistance (SAR) was induced in all treatment groups, a response centered around a glycerol-3-phosphate (G3P)-mediated pathway was exclusively observed in canola plants treated with PA23 alone. Activation of these defense mechanisms by PA23 involved production of reactive oxygen species as well as pronounced thylakoid membrane structures and plastoglobule formation in leaf chloroplasts. PA23 therefore primes defense responses in the plant through the induction of unique local and systemic regulatory networks. / October 2016

Brassica napus ist eine der wichtigsten Pflanzen in der Landwirtschaft. Pathogene verursachen jährlich große Ertragsverluste. Im Rahmen dieser Arbeit wurden die Interaktionen zwischen der Nutzpflanze Brassica napus bzw. der Modellpflanze Arabidopsis thaliana und dem phytopathogenen Pilz Verticillium longisporum untersucht. Verticillium longisporum ist ein auf Brassica spezialisierter Pilz, der die sogenannte Verticillium-Welke verursacht. Er dringt in die Wurzeln der Pflanze ein und steigt durch die Leitgefäße in den Spross auf. Die Pflanze zeigt in Folge der Infektion vor allem einen stark verkürzten Spross, Chlorosen und eine Notreife. Für die Experimente wurde Brassica napus und Arabidopsis thaliana mit Verticillium longisporum infiziert. Die Emissionen von Volatilen (volatile organic compounds (VOC)) der Pflanzen wurden sowohl ober- als auch unterirdisch bezüglich sich ändernder VOCs analysiert. Bei der Probennahme wurde darauf geachtet, die Pflanzen nicht zu verletzen und durch Messungen bedingten Stress zu minimieren. Auch während der Messungen der Wurzel-emissionen wurden die Pflanzen nicht aus ihrem Substrat entfernt, sondern innerhalb dessen gemessen. Während sich das Duftspektrum der Wurzeln von Brassica napus nicht änderte, emittierten die Sprosse infizierter Brassica Pflanzen signifikant mehr Dimethyldisulfid, ß-Ionon und ß-Cyclocitral. Bei der Infektion von Arabidopsis thaliana mit Verticillium longisporum hingegen spielten diese VOCs keine Rolle. Im zweiten Teil der Arbeit wurde die Vermutung überprüft, dass sich im Infektionsverlauf ändernde VOCs als Abwehrmoleküle dienen könnten. Hierfür wurde ein Bioassay entwickelt und zwei weitere pathogene Pilze, Gaeumannomyces graminis var. triciti und Sclerotinia sclerotiorum, unterschiedlicher Spezialisierung einbezogen. Wir setzten sie Dimethyldisulfid und ß-Ionon in unterschiedlichen Konzentrationen aus. Sowohl Dimethyldisulfid als auch ß-Ionon zeigten nur eine geringe fungizide Wirkung, gemessen am Myzelwachstum, gegen den Brassica-Spezialisten Verticillium longisporum. Gaeumannomyces graminis var. triciti wurde bereits bei geringeren Konzentrationen gehemmt. Sclerotinia sclerotiorum reagierte nicht oder sogar positiv auf die VOCs. Die (Mikro-) Sklerotienbildung wurde nur bei Verticillium longisporum beeinflusst. ß-Ionon unterstützte diese Entwicklung signifikant.

Submitted by Reginaldo Soares de Freitas (reginaldo.freitas@ufv.br) on 2016-04-18T16:16:44Z No. of bitstreams: 1 texto completo.pdf: 350102 bytes, checksum: f63374577f4c51e4a93a1ed9f2503a88 (MD5) / Made available in DSpace on 2016-04-18T16:16:44Z (GMT). No. of bitstreams: 1 texto completo.pdf: 350102 bytes, checksum: f63374577f4c51e4a93a1ed9f2503a88 (MD5) Previous issue date: 2015-07-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Trichoderma spp., antagonistas a vários fitopatógenos, são comumente isoladas do solo, da rizosfera, e como endofíticos. Nosso objetivo foi selecionar isolados de Trichoderma spp. nas culturas do feijão e da soja em Minas Gerais e avaliar o antagonismo a S. sclerotiorum, agente causal do mofo-branco de ambas as culturas. Obtiveram-se 48 isolados, sendo 30 da rizosfera, 11 epifíticos, quatro endofíticos e três de restos culturais. Com base no sequenciamento das regiões ITS, TEF1-α e RPB2, incluíram-se os isolados em oito espécies de Trichoderma: 29 como T. harzianum; 5 como T. koningiopsis; 4 como T. hamatum; 4 como T. atroviride; 2 como T. asperelloides; 2 como T. longibrachiatum; 1 como T. asperellum e 1 como T. neokoningii. Oito isolados inibiram completamente o crescimento do patógeno em teste de pareamento. Oito isolados foram os mais eficientes no crescimento em meio de cultura. Vinte e quatro isolados foram os mais eficientes em parasitar escleródios no solo, com 79-99% de eficiência. Em ágar-água, 31 isolados inibiram a germinação miceliogênica entre 78-100%, e sete isolados inibiram a germinação carpogênica em mais de 85%. Sete isolados inibiram 100% a infecção em folíolos destacados e um isolado inibiu em 79% a infecção em hastes destacadas. Dois isolados de T. harzianum, UN34 e IM2, foram os mais promissores: UN34 por reduzir a sobrevivência e as germinações miceliogênica e carpogênica de escleródios; e IM2 por reduzir a infecção em folíolos e hastes destacados. De acordo com os resultados, existe um potencial dos isolados de Trichoderma spp. no controle biológico de S. sclerotiorum. / Trichoderma spp., antagonists to plant pathogens, are commonly isolated from soil, rhizosphere, and as endophytic. We aimed to select Trichoderma spp. isolates from bean and soybean crops in Minas Gerais and to evaluate their antagonism to S. sclerotiorum, the causal agent of white mold on both crops. We got 48 isolates: 30 rhizospheric, 11 epiphytic, four endophytic, and three isolates from crop debris. Based on the sequencing of ITS, TEF1-α, and RPB2 regions, the isolates were classified in eight Trichoderma species: 29 as T. harzianum, 5 as T. koningiopsis, 4 as T. hamatum, 4 as T. atroviride, 2 as T. asperelloides; 2 as T. longibrachiatum, 1 as T. asperellum, and 1 as T. neokoningii. Eight isolates completely inhibited pathogen growth in dual culture test. Eight isolates were the most efficient in growing in culture medium. Twenty-four isolates were the best in parasitizing sclerotia in soil, with 79-99% of efficiency. In water-agar, 31 isolates inhibited miceliogenic germination from 78-100%, and seven isolates inhibited the carpogenic germination by more than 85%. Seven isolates inhibited 100% infection on detached leaflets and one isolate inhibited 79% infection on detached stems. Two isolates of T. harzianum, UN34 and IM2, were the most promising: UN34 for reducing the survival and both miceliogenic and carpogenic germination of sclerotia; and IM2 for reducing infection in both leaflets and stems. According to the results, there is a potential of the isolates of Trichoderma spp. in the biocontrol of S. sclerotiorum.