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Hall, R. J. "Modelling fungicide resistance." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599864.
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Fungicide resistance, whereby a mutation conferring reduced sensitivity to chemical control arises and spreads through a fungal population, severely inhibits the successful control of crop disease. Mathematical models play a vital role in assessing the risk of invasion of fungicide-resistant pathogens, and in the design of effective resistance management strategies. In this thesis, I investigate the factors affecting the invasion of resistance in heterogeneous crop environments. I develop a simple, nonlinear model for fungicide resistance which, improving on existing work, incorporates the dynamics of the host crop and quantities how the amount, decay and timing of a fungicide dose affect selection for resistance. The model structure is similar to those used to describe antibiotic resistance, and hence much of the analysis presented here applies more generally to drug and pesticide resistance. I identify a threshold for the invasion of resistance in terms of two key parameters, both of which are amenable to estimation in the field. These are the fitness of the resistant strain relative to the wild-type, and treatment efficacy (which summarises how control inhibits pathogen survival and reproduction). Using a discrete, stochastic formulation of the model, I demonstrate that this threshold is robust to the effects of demographic stochasticity, and estimate the probabilities of resistance pre-existing or emerging during treatment. In the final section of the thesis, I extend the simple model to examine the dynamics of multiple pathogen strains, the effects of seasonal disturbance to the host (through planting and harvesting) on persistence of the resistant pathogen, and how the scale of pathogen dispersal affects the spatial propagation of resistance.
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Reis, Renato Ferrari dos [UNESP]. "Esporulação in vivo, período de suscetibilidade dos tecidos e reação de tangerinas e híbridos a Alternaria alternata." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/105230.
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Este trabalho teve como objetivos determinar o efeito da idade da lesão de mancha marrom de Alternária (MMA) na produção conidial em folhas, ramos e frutos, a produção conidial sob diferentes condições de umidade relativa, a influência da aplicação de fungicidas na supressão da produção de conídios, o efeito da idade de maturação de folhas na suscetibilidade ao patógeno e a influência do tamanho de frutos na suscetibilidade à Alternaria alternata. A reação de espécies cítricas à MMA também foi avaliada. A esporulação em folhas teve início cerca de 10 dias depois do aparecimento de lesões de mancha marrom de Alternária, sendo que a maior produção de conídios ocorreu a partir de 20 dias, estendendo-se até 40 dias de idade. A produção de conídios foi superior em folhas do que em ramos ou frutos. A esporulação por unidade de área de lesão em folhas foi maior nos tangelos Minneola e Orlando , em relação ao tangor Murcott . A produção conidial em lesões de folhas foi mais abundante a partir de 85, 92,5, 96 e 100% de umidade relativa. A aplicação de fungicidas do grupo das estrobilurinas e dos cúpricos suprimiu a esporulação em lesões nas folhas por cerca de 14 a 21 dias após a aplicação. Folhas de tangelo Minneola apresentaram maior quantidade e maiores tamanhos de lesões até 20 dias de idade. O híbrido Nova foi o mais resistente entre os materiais genéticos estudados, sendo que folhas a partir de 16 dias de idade...
The objectives of this study were to evaluate: i) the effect of age of Alternaria brown spot (ABS) lesions on conidial production on leaves, twigs and fruit, ii) conidial production under different relative humidities, iii) influence of fungicide application on conidial production and iv) effect of leaf age on susceptibility to the disease and the influence of fruit size on the severity of brown spot. The reaction of the different citrus species to ABS was also studied. Sporulation on leaves began about 10 days after symptoms developed, was abundant from 20 to 40 days, and declined thereafter. Conidial production was far greater on leaf than fruit or twig lesions. Spore production per unit area of leaf lesion was greater on the more susceptible hybrids, Minneola and Orlando tangelos than on the less susceptible Murcott tangor. Conidial production on leaf lesions was more abundant at 85, 92.5, 96 and 100% relative humidity (RH) and almost nil at lower RH. Application of pyraclostrobin, trifloxyztrobin, azoxystrobin and copper fungicides suppressed the sporulation on leaf lesions for about 14 to 21 days after application. Minneola tangelo leaves had the greatest number and the largest lesions by 20 days or later. The Nova and Murcott hybrids were the most resistant of the cultivars and leaves showed few lesions when they were 16-days-old or older at inoculation. Leaves of Dancy tangerine were more susceptible than on leaves of Orlando tangelo and the Sunburst mandarin. For disease severity, there was a significant... (Complete abstract click electronic access below)
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Almeida, Taís Ferreira de. "Mancha preta dos citros: expressão dos sintomas em frutos pela inoculação com conídios e controle do agente causal (Guignardia citricarpa) /." Jaboticabal : [s.n.], 2009. http://hdl.handle.net/11449/105216.
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Resumo: A mancha preta dos citros (MPC) doença causada pelo fungo Guignardia citricarpa Kiely [anamorfo: Phyllosticta citricarpa (McAlp.) Van der Aa], é a principal doença fúngica da cultura no Brasil. Todas as variedades de laranjeiras doces são suscetíveis ao patógeno, que deprecia comercialmente os frutos, além de provocar sua queda prematura e elevar substancialmente o custo de produção. Até o presente momento, informações acerca da etiologia da doença são escassas. Portanto, o presente trabalho teve como objetivos: determinar os tipos de sintomas expressos por G. citricarpa em frutos cítricos inoculados com suspensão de conídios; desenvolver uma metodologia de inoculação de G. citricarpa a qual seja eficiente e permita estabelecer relações qualitativa e quantitativa, tanto em termos de níveis de severidade e tipos de inóculo; determinar em casa de vegetação o período de suscetibilidade dos frutos de laranjeira 'Pêra-Rio' a G. citricarpa; verificar a influência da forma endofítica de G. mangifera na expressão de sintomas de G. citricarpa e; avaliar a relação da eficiência de controle químico da MPC versus o tempo de exposição dos frutos à descarga de conídios de G. citricarpa. Foi observado que G. citricarpa inoculada em suspensão conidial em frutos de laranjeira 'Pêra-Rio' produzem sintomas do tipo mancha dura, mancha sardenta, mancha virulenta e falsa melanose. Quando inoculada em frutos de tangor 'Murcott' produzem sintomas do tipo falsa melanose e mancha dura. Frutos de laranjeira 'Pêra-Rio' mostraram-se mais suscetíveis a G. citricarpa que o tangor 'Murcott'. A metodologia de inoculação de conídios de G. citricarpa, mostrou-se eficiente, prática e rápida, permitindo quantificar o inóculo, fato inovador. Em relação à suscetibilidade, os frutos de laranjeira 'Pêra-Rio' quando inoculados... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: Citrus black spot (CBS), caused by Guignardia citricarpa Kiely [anamorph: Phyllosticta citricarpa (McAlp.) Van der Aa], is of the most import citrus disease in Brazil. Practically, all varieties of sweet oranges are susceptible to pathogen, which depreciates commercially the fruits, causes drop prematurely and increase substantially the cost of production. Until now, information about the etiology of the disease is scarce. Therefore, this study aimed to determine the types of symptoms expressed by G. citricarpa in citrus inoculated with conidial suspension, to develop a method of inoculation with G. citricarpa which to be efficient and allow a qualitative and quantitative relations with levels of severity and inoculum types, to determine in greenhouse the period of susceptibility sweet orange fruits of 'Pêra-Rio' to G. citricarpa; the influence of endophytic form of G. mangiferae in the suppression of symptoms of G. citricarpa; and to evaluate the efficiency of chemical control of CBS vs exposure time of fruit to discharge of conidia of G. citricarpa. Conidia of G. citricarpa inoculated in sweet orange Pêra-Rio produced symptoms of the types: hard spot, freckled spot, virulent spot and false melanose. When conidia inoculated in 'Murcott' tangor fruits the symptoms were of the type false melanose hard spot. Sweet orange fruits showed more susceptible than 'Murcott' tangor. The methodology of inoculation of conidia used in this work showed very efficient and practice allowing discriminative studies related to the inoculum and, additional alternative to studies related to Citrus-G. citricarpa pathosystem. For the susceptibility, sweet orange fruits with 4.5 cm diameter, inoculated with G. citricarpa showed 56.94% of fruit with symptoms of MPC, 50% of fruits with 5.5 cm diameter and 27.75% when inoculated with ≥ 7 cm in diameter, is only... (Complete abstract click electronic access below)
Orientador: Antonio de Goes
Coorientador: Renato Ferrari dos Reis
Banca: Jaime Maia dos Santos
Banca: Edson Luiz Furtado
Banca: Rita de Cássia Panizzi
Banca: Marcel Bellato Spósito
Doutor
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Zziwa, Miriam C. N. "Fungicide resistance to morpholine and piperidine fungicides in barley and wheat powdery mildew, Erysiphe graminis D.C." Thesis, University of Edinburgh, 1999. http://hdl.handle.net/1842/27744.
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This work was carried out to study the sensitivity of barley and wheat powdery mildew (Erysiphe graminis f.sp. hordei and E. graminis f.sp. tritici respectively) to morpholine fungicides. Morpholine fungicides are classified as compounds with a low risk of resistance development. On the other hand, barley and wheat powdery mildews belong to the group of high risk fungi as far as development of fungicide resistance is concerned. Firstly, mildew isolates collected in the UK were assessed, over the period 1992 to 1995, for their sensitivity to three morpholine fungicides (tridemorph, fenpropimorph and fenpropidin). Barley isolates tended to be more sensitive to the fungicides than wheat isolates. In general, the barley mildew isolates were less sensitive to tridemorph than to fenpropimorph and fenpropidin. Cross resistance was found between fenpropimorph and fenpropidin but there was no significant correlation between barley mildew sensitivity to tridemorph and either fenpropimorph or fenpropidin. Isolates from Scotland were significantly less sensitive to fenpropimorph and fenpropidin than isolates from England. The wheat isolates tended to be more sensitive to fenpropidin than to fenpropimorph. There was no evidence of cross resistance between fenpropimorph and fenpropidin with the wheat isolates tested. A shift towards insensitivity over the period of testing was found for fenpropimorph. Wheat isolates from Scotland were found to be significantly less sensitive to fenpropidin than isolates from England. Although variation in sensitivity among mildew isolates was recorded, the results of the monitoring work confirmed the findings of field experience that morpholines are continuing to maintain an effective control over barley and wheat mildew. The variation in sensitivity appeared to be as a continuous distribution, probably related at least in part to the use of bulk isolates for most of the sampling. There, was however, no evidence of any part of the population showing a very high level of resistance.
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Knowles, Tim C., Bruce Odom, and Del Wakimoto. "1998 Cottonseed Variety and Fungicide Evaluation." College of Agriculture, University of Arizona (Tucson, AZ), 1999. http://hdl.handle.net/10150/197280.
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Two upland cotton varieties (Deltapine 5415 and SureGrow 125) were subjected to various seed fungicide treatments to determine seedling emergence and vigor in a Mohave Valley field prone to Rhizoctonia infection of cotton seedlings. During 1998, cotton seedlings in this field exhibited symptoms associated with Rhizoctonia, Pythium, and Thielaviopsis fungi. Of the treatments examined in this study, Baytan+Thiram+Allegiance or Baytan+Ascend+Allegiance cotton seed treatments provided superior seedling disease protection. The Protégé+Allegiance fungicide treatment provided superior seedling disease protection when applied to Deltapine 5415 cotton seed, however seedling disease suppression was poor when the same treatment was applied to SureGrow 125. The Vitavax-PCNB+Allegiance and NuFlow M+Maxim+Apron were the least effective fungicide seed treatments examined in this study.
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Silveira, Savênia Bonoto da. "Toxicidade do tebuconazol em quatro espécies fitoplanctônicas dulcícolas subtropicais." reponame:Repositório Institucional da FURG, 2012. http://repositorio.furg.br/handle/1/4389.
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Dissertação (mestrado)-Universidade Federal do Rio Grande, Programa de Pós-Graduação em Biologia de Ambientes Aquáticos Continentais, Instituto de Ciências Biológicas, 2012.Submitted by Cristiane Gomides (cristiane_gomides@hotmail.com) on 2014-01-13T17:44:25Z No. of bitstreams: 1 0000010069.pdf: 1538365 bytes, checksum: c202c5228cc013b57b32fa76d75fad5d (MD5)
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A contaminação de ambientes aquáticos por compostos potencialmente tóxicos oriundos de atividades agrícolas é um problema que tem se agravado nos últimos anos. O tebuconazol é um fungicida amplamente usado na agricultura, frequentemente encontrado em águas naturais, inclusive no Rio Grande do Sul, e cuja toxicidade para o fitoplâncton não é conhecida. O objetivo deste trabalho foi avaliar a toxicidade do tebuconazol em quatro espécies fitoplanctônicas dulcícolas subtropicais. Foram montadas culturas estanque em triplicata testando seis diferentes concentrações de tebuconazol (10; 100; 500; 1.000; 5.000 e 10.000 μg L-1) para Cosmarium depressum var. planctonicum, Desmodesmus communis, Pediastrum boryanum e Spondylosium pygmaeum, assim como um controle somente com a microalga, sem a adição do tebuconazol, para verificar o crescimento padrão. Os experimentos foram mantidos por 13 dias, nos quais foram realizadas amostragens diárias nos 4 primeiros dias e a cada 72 h até o final do experimento para a análise de crescimento (clorofila-a e densidade celular) e parâmetros toxicológicos. As quatro cepas apresentaram diferença significativa de crescimento em relação ao controle, para C. depressum var. planctonicum nas concentrações 5.000 e 10.000 μg L-1, D. communis e P. boryanum em 1.000, 5.000 e 10.000 μg L-1 e S. pygmaeum a partir de 500 μg L-1. A EC50 (concentração que inibe 50% do crescimento) foi de 3.616 μg L-1 para C. depressum var. planctonicum, 3.246 μg L-1 para D. communis, 3.863 μg L-1 para P. boryanum e 1.851 μg L-1 para S. pygmaeum, sendo o S. pygmaeum a cepa mais sensível. Para LOEC (concentração mais baixa com efeito observado) e NOEC (concentração mais alta sem efeito observado) S. pygmaeum também apresentou concentrações mais baixas, seguido de C. depressum var. planctonicum, D. communis e P. boryanum.
Public concern has increased regarding the uncontrolled use of pesticides, including fungicides. Tebuconazol is a broad-spectrum fungicide that is used worldwide; however, its toxicity to phytoplankton is unknown. This work aims to evaluate the tebuconazol influence on the growth of four subtropical freshwater phytoplanktonic strains. Experimental cultures of Cosmarium depressum var. planctonicum, Desmodesmus communis, Pediastrum boryanum and Spondylosium pygmaeum were prepared with six tebuconazol concentrations (10, 100, 500, 1.000, 5.000 and 10.000 μg L-1), besides a control that was also prepared to measure the regular growth of each microalgae. The cultures (triplicates) were maintained for 13 days to determine both the growth (cellular density and chlorophyll-a content) and toxicological parameters. Tebuconazol inhibited the growth of all phytoplanktonic strains when they were exposed to 5.000 and 10.000 μg L-1. D. communis and P. boryanum were also inhibited when exposed to 1.000 μg L-1, while S. pygmaeum was inhibited since 500 to 10.000 μg L-1. The calculated EC50 was 3.616 μg L-1 to C. depressum var. planctonicum, 3.246 μg L-1 to D. communis, 3.863 μg L-1 to P. boryanum and 1.851 μg L-1 to S. pygmaeum, that was the most sensible strain to tebuconazol. LOEC and NOEC were also lower to S. pygmaeum followed by C. depressum var. planctonicum, D. communis and P. boryanum.
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Zeneratto, Marcos Antonio. "Ferrugem alaranjada da cana-de-açúcar : viabilidade técnica e econômica do controle químico, e curvas de progresso da doença sob condições naturais de cultivo. /." Jaboticabal, 2017. http://hdl.handle.net/11449/190661.
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Orientador: Antonio de GoesResumo: A ferrugem alaranjada da cana-de-açúcar (FA), causada por Puccinia kuehnii, é responsável por superior a 40% na produtividade de genótipos de cana-de-açúcar suscetíveis e intermediários. Nesse estudo foram realizados três experimentos. No experimento E1 foi avaliado o efeito do número de aplicações de fungicida piraclostrobina + epoxiconazole (PE) no município de Olímpia-SP, em E2 foi avaliado o efeito do número de aplicações de fungicida piraclostrobina + epoxiconazole (PE) no município de Catigua-SP, ambos em épocas distintas, e em E3 foi avaliado o efeito do volume de calda de PE no controle da doença. A partir dos dados obtidos nos experimentos E1 e E2, foi também avaliada a viabilidade econômica do controle da FA da cana-de-açúcar. Os experimentos foram realizados em dois locais, Olímpia e Catiguá, Estado de São Paulo, sendo empregada a cultivar SP81-3250, em quarto ciclo, após o terceiro corte, em estádio de desenvolvimento (Elongação do colmo; Crescimento intenso; Início do acúmulo de sacarose) da cultura. Em E1 e E2 usou-se o delineamento experimental em blocos ao acaso (DBC), com quatro tratamentos, sendo 0 (testemunha), 1, 2 e 3 aplicações. Cada parcela foi constituída por quatro linhas de 8 metros, espaçadas de 1,5 metros. Foram realizadas sete avaliações, com as quais determinou-se a severidade, a partir das quais foi obtida a área abaixo da curva de progresso da doença (AACPD). Também foi estimado o rendimento de colmos, expresso em tonelada de colmos por hectare... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The orange rust of sugarcane (FA), caused by Puccinia kuehnii, is responsible for over 40% in the yield of susceptible and intermediate sugarcane genotypes. Three experiments were performed in this study. In the E1 experiment, the effect of the number of applications of fungicide pyraclostrobin + epoxiconazole (PE) in the municipality of Olímpia-SP, in E2, was evaluated the effect of the number of applications of fungicide pyraclostrobin + epoxiconazole (PE) in the municipality of Catigua-SP, both at different times, and in E3 the effect of the volume of PE syrup on disease control was evaluated. From the data obtained in experiments E1 and E2, the economic viability of sugarcane FA control was also evaluated. The experiments were carried out at two locations, Olímpia and Catiguá, State of São Paulo, and the cultivar SP81-3250 was used, in the fourth cycle, after the third cut, at the development stage (Elongation of the stem, intense growth; sucrose) of the culture. In E1 and E2, the experimental design in randomized blocks (DBC) was used, with four treatments, being 0 (control), 1, 2 and 3 applications. Each plot was constituted by four lines of 8 meters, spaced of 1.5 meters. Seven evaluations were performed, with which the severity was determined, from which the area under the disease progress curve (AACPD) was obtained. The yield of stalks, expressed in ton of stems per hectare (TCH), was also estimated. In E3 a similar procedure was adopted, whose treatments were repres... (Complete abstract click electronic access below)
Mestre
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Leake, Christopher R. "The environmental fate of fungicide SN 539865." Thesis, University of Glasgow, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278444.
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Parnell, Stephen Robert. "The invasion and spread of fungicide resistance." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613759.
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Almeida, Taís Ferreira de [UNESP]. "Mancha preta dos citros: expressão dos sintomas em frutos pela inoculação com conídios e controle do agente causal (Guignardia citricarpa)." Universidade Estadual Paulista (UNESP), 2009. http://hdl.handle.net/11449/105216.
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A mancha preta dos citros (MPC) doença causada pelo fungo Guignardia citricarpa Kiely [anamorfo: Phyllosticta citricarpa (McAlp.) Van der Aa], é a principal doença fúngica da cultura no Brasil. Todas as variedades de laranjeiras doces são suscetíveis ao patógeno, que deprecia comercialmente os frutos, além de provocar sua queda prematura e elevar substancialmente o custo de produção. Até o presente momento, informações acerca da etiologia da doença são escassas. Portanto, o presente trabalho teve como objetivos: determinar os tipos de sintomas expressos por G. citricarpa em frutos cítricos inoculados com suspensão de conídios; desenvolver uma metodologia de inoculação de G. citricarpa a qual seja eficiente e permita estabelecer relações qualitativa e quantitativa, tanto em termos de níveis de severidade e tipos de inóculo; determinar em casa de vegetação o período de suscetibilidade dos frutos de laranjeira ‘Pêra-Rio’ a G. citricarpa; verificar a influência da forma endofítica de G. mangifera na expressão de sintomas de G. citricarpa e; avaliar a relação da eficiência de controle químico da MPC versus o tempo de exposição dos frutos à descarga de conídios de G. citricarpa. Foi observado que G. citricarpa inoculada em suspensão conidial em frutos de laranjeira ‘Pêra-Rio’ produzem sintomas do tipo mancha dura, mancha sardenta, mancha virulenta e falsa melanose. Quando inoculada em frutos de tangor ‘Murcott’ produzem sintomas do tipo falsa melanose e mancha dura. Frutos de laranjeira ‘Pêra-Rio’ mostraram-se mais suscetíveis a G. citricarpa que o tangor ‘Murcott’. A metodologia de inoculação de conídios de G. citricarpa, mostrou-se eficiente, prática e rápida, permitindo quantificar o inóculo, fato inovador. Em relação à suscetibilidade, os frutos de laranjeira ‘Pêra-Rio’ quando inoculados...
Citrus black spot (CBS), caused by Guignardia citricarpa Kiely [anamorph: Phyllosticta citricarpa (McAlp.) Van der Aa], is of the most import citrus disease in Brazil. Practically, all varieties of sweet oranges are susceptible to pathogen, which depreciates commercially the fruits, causes drop prematurely and increase substantially the cost of production. Until now, information about the etiology of the disease is scarce. Therefore, this study aimed to determine the types of symptoms expressed by G. citricarpa in citrus inoculated with conidial suspension, to develop a method of inoculation with G. citricarpa which to be efficient and allow a qualitative and quantitative relations with levels of severity and inoculum types, to determine in greenhouse the period of susceptibility sweet orange fruits of 'Pêra-Rio' to G. citricarpa; the influence of endophytic form of G. mangiferae in the suppression of symptoms of G. citricarpa; and to evaluate the efficiency of chemical control of CBS vs exposure time of fruit to discharge of conidia of G. citricarpa. Conidia of G. citricarpa inoculated in sweet orange Pêra-Rio produced symptoms of the types: hard spot, freckled spot, virulent spot and false melanose. When conidia inoculated in ‘Murcott’ tangor fruits the symptoms were of the type false melanose hard spot. Sweet orange fruits showed more susceptible than ‘Murcott’ tangor. The methodology of inoculation of conidia used in this work showed very efficient and practice allowing discriminative studies related to the inoculum and, additional alternative to studies related to Citrus-G. citricarpa pathosystem. For the susceptibility, sweet orange fruits with 4.5 cm diameter, inoculated with G. citricarpa showed 56.94% of fruit with symptoms of MPC, 50% of fruits with 5.5 cm diameter and 27.75% when inoculated with ≥ 7 cm in diameter, is only... (Complete abstract click electronic access below)
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Reis, Renato Ferrari dos. "Esporulação in vivo, período de suscetibilidade dos tecidos e reação de tangerinas e híbridos a Alternaria alternata /." Jaboticabal : [s.n.], 2006. http://hdl.handle.net/11449/105230.
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Resumo: Este trabalho teve como objetivos determinar o efeito da idade da lesão de mancha marrom de Alternária (MMA) na produção conidial em folhas, ramos e frutos, a produção conidial sob diferentes condições de umidade relativa, a influência da aplicação de fungicidas na supressão da produção de conídios, o efeito da idade de maturação de folhas na suscetibilidade ao patógeno e a influência do tamanho de frutos na suscetibilidade à Alternaria alternata. A reação de espécies cítricas à MMA também foi avaliada. A esporulação em folhas teve início cerca de 10 dias depois do aparecimento de lesões de mancha marrom de Alternária, sendo que a maior produção de conídios ocorreu a partir de 20 dias, estendendo-se até 40 dias de idade. A produção de conídios foi superior em folhas do que em ramos ou frutos. A esporulação por unidade de área de lesão em folhas foi maior nos tangelos Minneola e Orlando, em relação ao tangor Murcott. A produção conidial em lesões de folhas foi mais abundante a partir de 85, 92,5, 96 e 100% de umidade relativa. A aplicação de fungicidas do grupo das estrobilurinas e dos cúpricos suprimiu a esporulação em lesões nas folhas por cerca de 14 a 21 dias após a aplicação. Folhas de tangelo Minneola apresentaram maior quantidade e maiores tamanhos de lesões até 20 dias de idade. O híbrido Nova foi o mais resistente entre os materiais genéticos estudados, sendo que folhas a partir de 16 dias de idade... (Resumo completo, clicar acesso eletrônico abaixo)Abstract: The objectives of this study were to evaluate: i) the effect of age of Alternaria brown spot (ABS) lesions on conidial production on leaves, twigs and fruit, ii) conidial production under different relative humidities, iii) influence of fungicide application on conidial production and iv) effect of leaf age on susceptibility to the disease and the influence of fruit size on the severity of brown spot. The reaction of the different citrus species to ABS was also studied. Sporulation on leaves began about 10 days after symptoms developed, was abundant from 20 to 40 days, and declined thereafter. Conidial production was far greater on leaf than fruit or twig lesions. Spore production per unit area of leaf lesion was greater on the more susceptible hybrids, Minneola and Orlando tangelos than on the less susceptible Murcott tangor. Conidial production on leaf lesions was more abundant at 85, 92.5, 96 and 100% relative humidity (RH) and almost nil at lower RH. Application of pyraclostrobin, trifloxyztrobin, azoxystrobin and copper fungicides suppressed the sporulation on leaf lesions for about 14 to 21 days after application. Minneola tangelo leaves had the greatest number and the largest lesions by 20 days or later. The Nova and Murcott hybrids were the most resistant of the cultivars and leaves showed few lesions when they were 16-days-old or older at inoculation. Leaves of Dancy tangerine were more susceptible than on leaves of Orlando tangelo and the Sunburst mandarin. For disease severity, there was a significant... (Complete abstract click electronic access below)
Orientador: Antonio de Goes
Coorientador: Lavern Wayne Timmer
Banca: Eduardo Sanches Stuchi
Banca: Nelson Sidnei Massola Junior
Banca: Modesto Barreto
Banca: Antonio Baldo Geraldo Martins
Doutor
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MASSI, FEDERICO. "FUNGICIDE RESISTANCE IN GRAPEVINE DOWNY MILDEW MANAGEMENT: PHENOTYPIC AND GENOTYPIC CHARACTERIZATION OF PLASMOPARA VITICOLA POPULATIONS FOR RESISTANCE TO FUNGICIDES." Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/914468.
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Viticulture plays a role of prime importance within the world agricultural panorama. In 2020 the total world area planted with vineyards for all intended uses (wine and juices, table grapes and raisins), including young vines and not yet in production, was estimated at 7.3 Million ha by the International Organization of Vine and Wine in 2020. Within this vast production panorama, the Eurasian grapevine (Vitis vinifera L.) is the most cultivated species of grapevine due to the high quality of its grapes. One of the main problems affecting this species is that it is highly susceptible to infections of the phytopathogenic oomycete Plasmopara viticola (Berk. et Curt.) Berl. & De Toni. This pathogen is native to North America and with favorable climatic conditions can cause considerable damages to the grapevine production both from a qualitative and a quantitative point of view. P. viticola is a polycyclic pathogen, able to carry out numerous cycles of infection during a single vegetative grapevine season. Consequently, given the high susceptibility of V. vinifera cultivars to this pathogen in areas with frequent rainfall and moderate temperatures during the growing season, the cultivation of traditional varieties is not conceivable without frequent applications of fungicides.
Fungi and fungal-like organisms, such as the oomycetes, are highly adaptable to different environmental conditions, to host defense mechanisms and to fungicide selection. Repeated treatments with selectively active, site-specific fungicides, is frequently followed by the development of the phenomenon of fungicide resistance, which represents one of the major threats for downy mildew control and for modern agriculture in general, because it potentially leads to a reduction of disease control in the field (practical resistance). In order to preserve the effectiveness of such compounds, fungicide resistance must be carefully managed, and to this purpose proper disease control strategies have to be implemented by reducing the selection pressure associated to the fungicide use. The implementation of sound anti-resistance strategies is based on many factors: the risk of a particular fungicide class to evolve resistance, the risk related to the pathogen features, the agronomic risk associated to specific climatic conditions and the results obtained in sensitivity monitoring activities, that allow to characterize the fungicide sensitivity of pathogen strains or populations through bio tests and molecular diagnostic tools. In particular, monitoring of P. viticola populations for their sensitivities to the different active principles plays a key role in fungicide resistance management. However, for some fungicides these data are currently not yet present or incomplete, and actual testing methodologies to investigate some life stages of the pathogen are quite limited because they can provide only a qualitative description of resistance status.
Considering these current challenges, the aims of my PhD project were: a) to evaluate the sensitivity profile of P. viticola populations to different fungicide classes subjected to different disease pressure levels and spray programs in open field; b) to develop a new method based on flow cytometry and single-cell sorting for isolation of single sporangia in order to obtain a precise estimation of the percentage of sporangia able to positively infect grapevine plants in the population; c) to characterize possible resistant strains for the mechanism of resistance and pathogenicity.
In general, among the populations tested we found a good sensitivity for the fungicides under investigation. Sporadic cases of resistance were detected, and for some of them it was possible to link the resistant phenotype to single point mutations in the gene encoding the target protein.
Depending on the life stages of the pathogen under investigation, more quantitative or qualitative data were obtained according to the testing methods available. This made it necessary to develop a further tool to make the investigations on the asexual reproduction stages of the pathogen more homogeneous to those of sexual reproduction. Flow cytometry and single-cell sorting have proven to be excellent technologies to bridge this gap, and the quantitative method here developed and proposed could be positively implemented in future for large-scale monitoring investigations of fungicide resistance.
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Kildea, S. "Fungicide resistance in the heat pathogen mycosphaerella graminicola." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517380.
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Pijls, C. F. N. R. M. J. "Population genetics of fungicide resistance in Septoria tritici." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308103.
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Leake, Christopher Robert. "The environmental fate of the fungicide SN 539865." Thesis, University of Strathclyde, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249025.
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Kellerman, Mareli. "Fungicide resistance and control of citrus green mould." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86776.
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Hocart, M. J. "Fungicide resistance and parasexual recombination in Pseudocercosporella herpotrichoides." Thesis, University of Nottingham, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376495.
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Hu, Jiahuai. "Phytophthora nicotianae: Fungicide Sensitivity, Fitness, and Molecular Markers." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/26416.
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Mefenoxam has been a premier compound for Phytophthora disease control in the nursery industry for 30 years. The primary objectives of this research were to examine whether Phytophthora species have developed resistance to this compound and to investigate fungicide resistance management strategies. Phytophthora nicotianae, a destructive pathogen of numerous herbaceous and some woody ornamental plants, was used as a model system. P. cinnamomi, a major pathogen of a wide range of tree species and shrub plants, was also included for comparison.
Twenty-six isolates of P. nicotianae were highly resistant to mefenoxam with a mean EC50 value of 326.5 µg/ml while the remaining 70 were sensitive with an EC50 of <0.01 µg/ml (Label rate: 0.08µg/ml). All resistant isolates were recovered from herbaceous annuals and irrigation water in 3 Virginia nurseries. Resistant isolates were compared with sensitive ones using seedlings of Lupinus â Russell Hybridsâ in the absence of mefenoxam for relative competitive ability. Resistant isolates out-competed sensitive ones within 3 to 6 sporulation cycles. Resistant isolates exhibited greater infection rate and higher sporulation ability than sensitive ones.
No mefenoxam resistant isolates were identified in P. cinnamomi. All 65 isolates of P. cinnamomi were sensitive to mefenoxam with an EC50 of < 0.04 ï g/ml. Attempts to generate mutants with high resistance to mefenoxam through UV mutagenesis and mycelial adaptation were not successful. However, there were significant reductions in sensitivity to mefenoxam; those slightly resistant mutants carried fitness penalties, which may explain why P. cinnamomi remains sensitive to mefenoxam.
The effect of propamocarb hydrochloride on different growth stages of Phytophthora nicotianae was evaluated in search for an alternative fungicide. Propamocarb greatly inhibited sporangium production, zoospore motility, germination and infection. However, it has little inhibition of mycelial growth and infections. Propamocarb can be used as an alternative fungicide to mefenoxam where mefenoxam resistance has become problematic. However, it must be used preventively; i.e. before infections occur.
The genetic inheritance of mefenoxam resistance in P. nicotianae was studied using F1 progenies of a cross between resistant and sensitive isolates. The F1 progenies segregated for mefenoxam resistance in ratio of 1R:1S, indicating the mefenoxam resistance is controlled by a single dominant gene. One RAPD marker putatively linked to resistant locus in repulsion phase was obtained by bulked segregant analysis and was converted to the SCAR marker. This marker is capable of differentiating mefenoxam resistant populations from sensitive populations included in this study.Ph. D.
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Sewell, Thomas Richard. "Efficacy of fungicides on coexisting Leptophaeria spp. causing phoma stem canker on winter oilseed rape." Thesis, University of Hertfordshire, 2017. http://hdl.handle.net/2299/18990.
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Phoma stem canker is a disease of oilseed rape (Brassica napus) caused by closely related plant pathogens Leptosphaeria maculans and L. biglobosa. It is an economically important disease, causing annual yield losses of approximately £770 million worldwide. When colonising oilseed rape, L. maculans and L. biglobosa exist in close proximity on the leaf, competing for resources as they move through the main leaf vein and into the stem. Fungicides are commonly used to decrease severity of phoma stem canker on oilseed rape. However, the efficacy and longevity of active chemicals is under threat from evolution of resistance in pathogen populations and government legalisation. Moreover, it has been suggested that both L. maculans and L. biglobosa differ in their sensitivity to azoles, and important class of fungicides that are used to control the disease through the inhibition of lanosterol 14-α demethylase (erg11, CYP51). This project aims to further understand the role that fungicides have in controlling phoma stem canker by investigating their efficacy against L. maculans and L. biglobosa in crops, in vitro and in planta. In field experiments, established in Cambridgeshire across four cropping seasons, the fungicide mixture penthiopyrad (SDHI) plus picoxystrobin (QoI) was as effective at controlling phoma leaf spotting and phoma stem canker in winter oilseed rape as prothioconazole (DMI), suggesting that both fungicides could be used to reduce phoma stem canker symptoms. The two pathogens differed in their growth rates in vitro, with L. biglobosa growing faster than L. maculans when untreated or treated with lower fungicide concentrations. Fungicide sensitivity assays suggest that L. maculans and L. biglobosa are both sensitive to DMI, SDHI and QoI fungicides and that differences between the species are minor. Prothioconazole and penthiopyrad + picoxystrobin had a similar efficacy on oilseed rape cotyledons colonised with either L. maculans or L. biglobosa. There was no difference between species on prothioconazole treated plants, although there was a difference between L. maculans and L. biglobosa when treated with 20 μg/ml penthiopyrad + picoxystrobin. Heterologous yeast expression of LmCYP51B and LbCYP51B with fungicide sensitivity testing of the yeast transformants suggests that LmCYP51B and LbCYP51B are similarly sensitive to azole fungicides flusilazole, prothioconazole-desthio and tebuconazole. These findings are supported by homology protein modelling, which predicts that LmCYP51B and LbCYP51B are structurally very similar, specifically at the azole-binding site. In conclusion, fungicides are still an effective control method for reducing phoma stem canker symptoms caused by Leptosphaeria species in the UK, and a useful tool to in the sustainable production of oilseed rape.
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Goodenough, Lynn. "Investigations into the mode of action of dimethomorph in Phytophthora species and Bremia lactucae." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337763.
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Zhu, Qinghua. "Resistance risk assessment of cyprodinil against cereal eyespot : Pseudocercosporella herpotrichoides." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365702.
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Barton, Wayne Robert. "Sensitivity of Sclerotinia homoeocarpa to the DMI fungicide propiconazole." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ40395.pdf.
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Wallace, R. J. "Fungicide resistance of Trichoderma spp. colonising freshly-felled timber." Thesis, University of Portsmouth, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316411.
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Dooley, Hilda. "Fungicide-resistance management tactics : impacts on Zymoseptoria tritici populations." Thesis, University of Reading, 2015. http://centaur.reading.ac.uk/49314/.
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Azoles and Succinate Dehydrogenase Inhibitors (SDHIs) are the main fungicides available for septoria tritici blotch control, causal agent Zymoseptoria tritici. Decline in azole sensitivity, in combination with European legislation, poses a threat to wheat production in Ireland. Azole fungicides select CYP51 mutations differentially; it was hypothesised that using combinations of azoles could be an effective anti-resistance tool. Naturally inoculated field experiments were carried out in order to understand the impacts of using combinations of azoles, epoxiconazole and metconazole, on azole sensitivity. Approximately 3700 isolates were isolated and their sensitivity to both azoles analysed. Findings showed that limiting the number of applications, by alternating each fungicide, slowed selection for reduced azole sensitivity. Limiting azole use by reducing doses did not reduce selection for decreased azole sensitivity. Although not complete, cross-resistance was observed between the two azoles, which will lead to general reduction in azole sensitivity. A sub-selection of isolates from each treatment at each location were analysed for changes in the CYP51 gene. Sequence analysis identified 49 combinations of mutations in the CYP51 gene, and three different inserts in the CYP51 promoter. Intragenic recombination also featured in these populations. Baseline studies of five new SDHIs were carried out on 209 naturally infected, non-SDHI-treated isolates. With the exception of fluopyram, cross-resistance was apparent between the SDHIs. Analysis of 2300 isolates found that when compared to the solo products, mixing the SDHI isopyrazam and the azole epoxiconazole increased epoxiconazole sensitivity, but had no apparent effect on isopyrazam sensitivity. SDHI resistance-conferring mutations were absent in the baseline and experimental isolates. As long as azoles are used, Z. tritici populations will continue to evolve towards resistance. Combining different modes-of-action, SDHIs and multi-sites, with azoles will relieve some of that selective pressure. To get the best out of available fungicides, they should be used in combination with host resistance and good crop management practices.
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Howard, Kay. "The effect of the fungicide phosphite on ectomycorrhizal fungi." Thesis, Howard, Kay ORCID: 0000-0003-3977-1243 (2001) The effect of the fungicide phosphite on ectomycorrhizal fungi. PhD thesis, Murdoch University, 2001. https://researchrepository.murdoch.edu.au/id/eprint/3215/.
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In Western Australia, the fungicide phosphite is being applied to selected native plant communities in order to reduce the impact of the root and collar rot pathogen, Phytophthora cinnamomi. The effect of this fungicide on the growth and function of ectomycorrhizal (ECM) fungi and their mycorrhizas was unknown. Taking the hypothesis that phosphite has a deleterious effect on mycorrhizal fungi, this study explored potential detrimental effects of phosphite on early colonising ectomycorrhizal fungi.
Ten isolates of Scleroderma and Pisolithus from Western Australia, isolated from a range of host plants. These isolates were partnered with Agonis flexuosa, Melaleuca scabra, Eucalyptus globulus, E. sieberi and four clonal lines of E. marginata (jarrah) in vitro. The isolates that formed a mantle, Hartig net and epidermal cell elongation characteristic of a successful symbiosis, were chosen for further studies on two contrasting E. marginata clonal lines, that were resistant or susceptible to P. cinnamomi. Foliar drenching with phosphite induced different responses in the two clonal lines when they were non-mycorrhizal. Phosphite decreased root production in the resistant clone, and increased the number of plantlets that produced roots in the susceptible clonal line. Generally, 3 g phosphite/L reduced the host response to mycorrhizal infection, and mycorrhizas reduced root responses to phosphite compared to those seen in non-mycorrhizal plants.
To determine if phosphite could have a direct inhibitory effect on the hyphae of ECM fungi, three isolates of Laccaria, Scleroderma and Pisolithus were grown in pure culture, on media containing a range of phosphite and phosphate concentrations. The biomass of Laccaria generally decreased as phosphite concentration increased at low phosphate concentrations. As phosphate concentration increased, the biomass of each Laccaria isolate generally increased irrespective of phosphite concentration. In hyphae of the three isolates of Laccaria, the increasing concentrations of phosphate in the media resulted in significant accumulation of phosphate. In two isolates, external phosphite supply had no effect on phosphate uptake. Scleroderma and Pisolithus tolerated the same concentration of phosphite as phosphate, while Laccaria was more sensitive to phosphite. There was a significant difference in growth between Laccaria isolates, while there was less variation between isolates of Scleroderma and Pisolithus. Scleroderma was most sensitive with two isolates being killed by 40 mM and the third being killed by 100 mM phosphite, while 120 – 140 mM phosphite was fungicidal to Laccaria and Pisolithus isolates.
In the glasshouse, non-mycorrhizal seedlings of E. marginata, E. globulus and A. flexuosa were sprayed to run-off with 0 to 10 g phosphite/L, and then planted into soil naturally infested with early colonising mycorrhizal species. Phosphite had no effect on the percentage of roots infected with mycorrhizal fungi. In another experiment, E. globulus seedlings ectomycorrhizal with Scleroderma, Pisolithus and Descolea were treated with 0 to 10 g phosphite/L and infection of new roots by ectomycorrhizal fungi was assessed. At the recommended rate (5 g phosphite/L), phosphite had no effect on ectomycorrhizal formation, while at 10 g/L phosphite decreased infection by Descolea by 15%.
An in vitro study was undertaken on a clonal line of E. marginata to determine if the foliar application of 3 g phosphite/L had any effect on the ability of Scleroderma and Pisolithus spores to germinate and infect roots. There was no significant difference in the percentage of infected primary and lateral root tips in phosphite and control plants inoculated with Scleroderma or Pisolithus spores.
To determine if the soluble and cell wall bound peroxidases and phenolics involved in host defence responses are affected by phosphite treatment of the host, a series of interactions with E. marginata, ECM fungi and P. cinnamomi were examined. Phosphite significantly reduced P. cinnamomi lesion length in all mycorrhizal and non-mycorrhizal treatments and altered static peroxidase activity and phenolic concentrations in the roots of all non-mycorrhizal plants.
Phosphite did not induce changes in peroxidase activity or phenolic concentration in roots of the susceptible clone when in indirect contact with Pisolithus. However, there was a general increase in peroxidase activity and phenolic concentration in roots of the resistant clone in the presence of Pisolithus and P. cinnamomi. In contrast, phosphite decreased peroxidase activity in the susceptible clone in the presence of Scleroderma and had no effect on soluble or cell wall bound phenolics. Phosphite did not alter peroxidase activity or phenolic concentration in roots of the resistant clone challenged by P. cinnamomi in the presence of either Scleroderma or Pisolithus. In contrast, phosphite significantly increased peroxidase activity, and decreased soluble phenolic concentration in the roots of the susceptible clone in the presence of Pisolithus.
A glasshouse trial examined the effect of foliar applied phosphite (3 g/L) on P. cinnamomi infection of roots of mycorrhizal E. marginata plants. Laccaria, Scleroderma and Pisolithus mycorrhiza were established with seedlings and a P. cinnamomi susceptible clonal line of E. marginata prior to phosphite treatment. P. cinnamomi zoospores were inoculated to the root zone 10 days after phosphite application. P. cinnamomi was recovered from 84% and 52% of the untreated seedlings and clonal plants respectively, whether they were ectomycorrhizal or not. By contrast, in phosphite treated plants, P. cinnamomi was recovered in 10% of seedlings and 6% of clonal plants. There was no difference in P. cinnamomi recovery between mycorrhizal types in seedlings and clonal plants. More P. cinnamomi was recovered from mycorrhizal than non-mycorrhizal clonal plants. There was no correlation between the extent of mycorrhizal fungal colonisation and the percentage of P. cinnamomi infected roots in clonal plants or seedlings.
Overall conclusions
Although only a few ECM fungi and host species were examined in this study, it appears that phosphite, when used at the recommended rate (5 g/L), may not have a detrimental effect on ECM formation. The concentration of phosphite that is fungicidal to ECM fungi in vitro is generally in excess of levels that would be found in treated plant tissues. However, when the recommended rate was exceeded it was shown that phosphite significantly decreased infection by Descolea.
This study has shown that there is variation between genera of ECM fungi, host plants, type of plant (clonal material or seedlings) in response to phosphite. However, this study did not take into account differing phosphate concentrations and its effect on phosphite and mycorrhizal interactions, which would further increase these variations. This demonstrates that generalisations cannot be made on the effect of phosphite on ECM fungi and ECM plants.
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Clark, L. J., E. W. Carpenter, and R. E. Call. "Fungicide Evaluations on Beans in Southeastern Arizona, 1994-1995." College of Agriculture, University of Arizona (Tucson, AZ), 1996. http://hdl.handle.net/10150/202442.
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Fungicidal evaluations were performed on pinto beans in two sites in 1994 and one site in 1995 to determine their effect on bean rust, white mold or common bacterial blight The results were mixed between sites and years, but in 1994 the untreated control yielded less than all of the treatments except one and the Fluazinam 500F 1 lb rate was the highest yielding treatment In 1995, no disease symptoms were observed in the field.
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Hine, Dick, Roy Whitson, Jim Armstrong, Don Howell, and Ron Cluff. "Fungicide Evaluations for the Control of Phymatotrichum Root Rot." College of Agriculture, University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/204052.
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Malone, James. "Interactions of the fungicide 2-aminobutane with potato tubers." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/28529.
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A synthetic route to 2-aminobutane (2-AB) was developed, which enabled the synthesis of specifically and uniformly 14C labelled 2-AB to be carried out. 14C labelling was employed as a means of detecting 2-aminobutane in tuber tissue samples. An analytical technique, based on acid extraction and scintillation counting, was developed for the determination of 2-AB residues in potato tubers. This allowed studies to be carried out on various factors influencing the efficiency of fumigation of potato tubers with 2-aminobutane. Using C 2-AB and a specially constructed small scale fumigation chamber, an investigation into the absorption and penetration of 2-AB into tubers was undertaken. The rate and extent of 2-AB absorption were studied, and also the effect of initial fumigant concentration and length of exposure period, on the final 2-AB residues in tubers. The depth of penetration was shown to be limited to the first 1 cm of tissue indicating that after initial absorption, the amine is firmly bound at or near the tuber surface. Thin layer chromatography of extracts from fumigated tubers,provided evidence which suggested that 2-AB is not metabolised by the tubers during the storage period. Damaged tubers were shown to absorb higher levels of 2-AB, and the effect of wound healing at different temperatures, prior to fumigation, was demonstrated. The preferential uptake of 2-aminobutane through tuberlenticels was highlighted as a possible cause of tuberto tuber variation in 2-AB residues. Studies showed that there was no appreciable loss of 2-AB from fumigated tubers during the storage period, and that transfer of 2-AB from tuber to tuber during air recirculation was very limited. The absorption of 2-AB by soil, straw and wood,was examined and identified as a likely sink for the amine fumigant, and this could contribute to the low 2-AB residues recorded for some commercial fumigations. A comparison of the antifungal activity of the optical isomers of 2-aminobutane, confirmed that the R-(-)- enantiomer was more active than the corresponding S-(+)- isomer, or racemic mixture, against the fungi responsible for gangrene and skin spot in potato tubers.
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Larson, Ben James. "Integrated management of Cercospora leaf spot on sugar beet." Thesis, Montana State University, 2004. http://etd.lib.montana.edu/etd/2004/larson/LarsonB04.pdf.
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Zhou, Tian. "Quantification of Fungicide Resistance in Cercospora sojina Populations and Development of a Fungicide Application Decision Aid for Soybean in the Mid-Atlantic U.S." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/102925.
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Soybean is an important source of protein in animal feed, and growing demand for meat consumption worldwide has led to increased soybean production. Over 120 million metric tons of soybean were harvested in the United States in 2018, approximately one-third of the world production. In the Mid-Atlantic region, soybean is one of the most valuable field crops. Major foliar diseases that reduce soybean yield in the Mid-Atlantic region are frogeye leaf spot (FLS) and Cercospora leaf blight. In addition to crop rotation and host resistance, foliar fungicides, often with quinone outside inhibitor (QoI) active ingredients, are used to manage these soybean foliar diseases. Yield benefits of foliar fungicides have been inconsistent and this may be the result of low disease pressure, unfavorable environmental conditions for disease development, or the presence of fungal pathogen populations that have developed resistance to fungicides. The objectives of this research were 1) to develop a pyrosequencing-based assay to rapidly quantify QoI resistance frequencies in Cercospora sojina, the causal agent of FLS, 2) to examine the effects of fungicide application timings, disease pressure, and environmental factors on soybean yield, and 3) to develop a weather-based soybean foliar fungicide application decision aid for the Mid-Atlantic U.S. using a threshold decision rule. A pyrosequencing assay targeting the G143A mutation was designed, and a Virginia survey of C. sojina populations indicated that the G143A mutation conferring QoI resistance is widespread. In small plot fungicide application timing experiments, five weekly fungicide applications starting at beginning pod (R3) resulted in the greatest yield, but for single fungicide applications, R3 or 1 week after R3 resulted in the greatest yields. There was positive relationship between the cumulative number of disease favorable days (mean daily temperature 20-30°C and ≥ 10 hours of relative humidity >90%) from planting to R3 and disease severity at the full pod stage (r = 0.97, P = <0.01). Higher disease severity was associated with greater yield loss (r2 =0.53, P = 0.10) suggesting foliar fungicide applications are more likely to have yield benefits as the number of disease favorable days prior to R3 increase. A disease favorable-days threshold (FDT) using the environmental parameters indicated above was evaluated in on-farm experiments throughout Virginia, Maryland, and Delaware. Based on decision rules, FDT = 8 three weeks prior to R3 was the best predictor of a yield benefit with an R3 fungicide application. The decision aid was also able to correctly predict when a fungicide application would not be profitable ≥90% of the time. This weather-based decision aid along with monitoring of fungicide resistance development within the region will provide soybean growers in the Mid-Atlantic U.S. with tools to maximize yields and profitability.Doctor of Philosophy
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Niver, Amy. "Impact of fall and spring fungicide applications on dollar spottitle." Connect to this title online, 2005. http://hdl.handle.net/1811/365.
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Thesis (Honors)--Ohio State University, 2005.Title from first page of PDF file. Document formattted into pages: contains, 20 p.; also includes graphics. Includes bibliographical references (p. 12-13). Available online via Ohio State University's Knowledge Bank.
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Meyer, Jack Robert. "Cultivar susceptibility and fungicide control of black dot root rot." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/meyer/MeyerJ0507.pdf.
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Lee, Suk-wah, and 李淑華. "Fungicide resistance and genetic diversity of Penicillium digitatum inHong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31226255.
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Spice, Nicola Jane. "Evaluating the use of fungal protoplasts to investigate fungicide action." Thesis, Nottingham Trent University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341273.
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Marine, Sasha Cahn. "Characterization of Fungicide Resistance in Venturia inaequalis Populations in Virginia." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/77359.
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Apple scab (causal organism: Venturia inaequalis) is an economically devastating disease of apples that is predominantly controlled with fungicides. Of the chemical classes currently available, the sterol-inhibiting (SI) and strobilurin (QoI) fungicides are the most commonly used. Recent observations indicate that V. inaequalis populations in Virginia have developed resistance to myclobutanil and other SIs. However, little is known about the frequency and distribution of SI and QoI resistance in Virginia's scab populations. The first objective of this research was to evaluate V. inaequalis populations in Virginia for SI and QoI resistance. Fungal isolates were collected from experimental orchards at the Alson H. Smith Jr., Agricultural Research and Extension Center (AHS AREC) and from commercial orchards in Virginia and Maryland. Sensitivities were determined by assessing colony growth at 19°C on potato dextrose agar (PDA) amended with 0 or 1.0 µg ml-1 of myclobutanil (SI) (N=87) or trifloxystrobin (QoI) (N=25) at 28 days. A range of fungicide sensitivity was observed for both chemical classes. The second objective of this research was to monitor the temporal dynamics of SI resistance over five sequential field seasons. To monitor shoot growth, neon rubber bands were placed over actively growing shoot tips following myclobutanil application or sample collection. Fungal isolates were collected from the same trees from 2007 through 2010 (N=176) and compared with isolates collected from wild apple seedlings (N=3). A continuum of SI resistance was observed for each year, and the V. inaequalis population exhibited a baseline shifted toward reduced sensitivity. The third objective of this research was to examine the spatial distribution of SI fungicide resistance within the tree canopy in a lower-density orchard (less than 150 trees A-1). Leaves collected from larger trees (>8m) in a lower-density orchard at the AHS AREC were analyzed for manganese deposition, pre- and post-mancozeb application. Fungal isolates (N=105) were collected from several locations within the canopy in replicated trees in the same orchard. Weather sensors also monitored the microclimates within those tree canopies. Spray deposition, microclimate and SI resistance were influenced by canopy location. The fourth objective of this research was to investigate potential SI resistance mechanisms. Previously classified isolates were screened for point mutations within the CYP51A1 gene (Appendix C), differences in polymorphic bands (alleles) (Appendix D), and differences in metabolism of myclobutanil (Appendix E). The consensus sequences for the CYP51A1 gene were identical for all isolates tested (N=9), and results from amplified fragment length polymorphism experiment (N=82) were inconclusive. There were, however, significant differences among incubation time and myclobutanil concentration in the bioassay (N=11). Our results indicate that myclobutanil is still an effective compound for control of apple scab in many areas of Virginia.Ph. D.
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Koenig, John L. "TIMING OF FUNGICIDE APPLICATIONS FOR THE MANAGEMENT OF DOLLAR SPOT." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253625623.
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Van, Der Heyden Hervé. "Spatial analysis of fungicide resistance mutations in Botrytis spp. populations." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119375.
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The objectives of this project were: 1) to study the spatial interactions of single nucleotide polymorphisms (SNPs) related to fungicide resistance within Botrytis cinerea populations isolated from grapes; 2) to study the spatial distribution patterns of SNPs related to fungicide resistance within B. cinerea populations in grape and within B. squamosa populations in onion; and 3) to compute sampling curves relative to mean SNP incidence estimation. In a first experiment, B. cinerea isolates were collected following a quadrat-based design (100 10x10m quadrats) in two commercial vineyards. The presence of 9 SNPs related to resistance to iprodione, boscalid, azoxystrobin and fenhexamid were detected using PCR-RFLP, PIRA-PCR and RT-qPCR assays. These data were spatially referenced and considered as a multivariate point pattern in a given vineyard. Spatial point patterns were analyzed by pairs, using an extension of Diggle's procedure for the analysis of nearest-neighbor distances. In this randomization testing procedure, the cumulative relative frequency distribution of the inter-SNP distances was used to characterize the spatial relationship between SNPs related to fungicide resistance. In the second experiment, two SNPs known to be responsible for boscalid resistance and one SNP known to be responsible for dicarboximide resistance in B. cinerea on grape were studied, in addition to one SNP responsible for dicarboximide resistance in B. squamosa on onion. One onion field was sampled in 2009 and another one was sampled in 2010 for B. squamosa, and two vineyards were sampled in 2011 for B. cinerea, for a total of four sampled sites. Sampling was carried following the same design as in the first experiment, except 10 samples were collected in each quadrat. Samples were analyzed by RFLP-PCR. The characterization of spatial distribution patterns was made through the fitting of discrete probability distributions. The level of mutations obtained in the first experiment was 90%, 64%, 67%, 33% and 1% for G143A, I86S, H272R, H272Y and N230I, respectively. Our results show that three spatial relationships can arise when spatial point patterns representing the presence of SNPs related to fungicide resistance are compared by pairs: spatial exclusiveness (12%), spatial co-existence (31%) and absence of a spatial relationship (56%). Despite the fact that more than one half of the pairs of SNPs tested showed no spatial relationship, the presence of about a third of inclusive spatial relationships supports the models of co-existence between sensitive and resistant strains postulated in the literature, but suggests a higher level of complexity in the resistant-sensitive interactions. In the second experiment, the beta-binomial distribution was found to fit the data better than the binomial distribution for all data sets. This indicates local SNP aggregation among sampling units, as supported by estimates of the parameter θ of the beta-binomial distribution ranging from 0.09 to 0.23, with an overall median value of 0.20. On the basis of the spatial distribution patterns of SNP incidence that we found in Botrytis populations, sampling curves were developed for various levels of precision, emphasizing the importance of sampling for early detection of fungicide resistance in plant disease epidemiology.Les objectifs de ce projet étaient: 1) d'étudier les interactions spatiales entre polymorphismes nucléotidiques simples (PNS) associés à la résistance aux fongicides dans les populations de Botrytis cinerea provenant de raisins infectés; 2) d'étudier les patrons de distribution spatiale des PNS associés à la résistance aux fongicides au sein de populations de B. cinerea provenant de vignobles et de populations de Botrytis squamosa dans des champs d'oignions; et 3) de développer des courbes d'échantillonnages associées à l'estimation de l'incidence moyenne des PNS. Dans une première expérience, des isolats de B. cinerea ont été récoltés dans deux vignobles commerciaux en suivant une grille d'échantillonnage de 100 quadrats de 10x10m. La présence de 9 PNS associés à la résistance à l'iprodione, au boscalid, à l'azoxystrobine et au fenhexamid a été détectée par PCR-RFLP, PIRA-PCR et RT-qPCR. Les données ont été référencées spatialement et pour chaque vignoble, considérées comme un patron ponctuel multivarié. Les analyses ont été réalisées par paire, à l'aide d'une extension de la méthode de Diggle pour l'analyse des distances aux plus proches voisins. Dans cette procédure de test par randomisation, la distribution des fréquences relatives cumulatives des distances inter-PNS est utilisée afin de caractériser les patrons de relation spatiale entre PNS associés à la résistance aux fongicides. Dans une deuxième expérience, deux PNS associés à la résistance de B. cinerea au boscalid et un PNS associé à la résistance de B. cinerea aux dicarboximides ont été étudiés dans la vigne, en plus d'un PNS associé à la résistance de B. squamosa aux dicarboximides dans l'oignion. Pour B. squamosa, deux champs ont été échantillonnés, un en 2009 et un en 2010, et pour B. cinerea, deux champs ont été échantillonnés en 2011, pour un total de quatre sites d'échantillonnage. L'échantillonnage a été réalisé en suivant le même dispositif expérimental que pour la première expérience, à la différence que 10 échantillons ont été prélevés dans chaque quadrat. Les échantillons ont été analysés par PCR-RFLP, et les patrons de distribution spatiale ont été caractérisés sur base de l'ajustement des lois de distributions. Dans la première expérience, les proportions de PNS étaient de 90%, 64%, 67%, 33% et 1% pour G143A, I86S, H272R, H272Y et N230I, respectivement. Ces résultats démontrent que, lorsque les PNS associés à la résistance aux fongicides sont comparés par paires, trois types de relation spatiale peuvent survenir: l'absence de relation spatiale (56%), l'inclusion spatiale (31%) et l'exclusion spatiale (12%). En dépit du fait que plus de la moitié des paires de PNS testées ne montraient aucune relation spatiale, la présence de relation spatiale inclusive (31%) supporte les modèles de coexistence entre phénotypes sensibles et résistants, mais suggère un niveau de complexité supérieur. Pour la seconde expérience, la distribution bêta-binomiale s'ajustait mieux aux données que la distribution binomiale pour tous les jeux de données. Les valeurs estimées de l'indice d'agrégation θ étaient comprises entre 0.09 et 0.23 (valeur médiane de 0.20), indiquant une agrégation locale des PNS au sein d'une même unité d'échantillonnage. Finalement, en se basant sur les niveaux d'agrégation observés, des courbes d'échantillonnages ont été calculées pour différentes incidences de PNS et différents niveaux de précision. Ces résultats mettent ainsi l'emphase sur l'importance de l'échantillonnage pour une détection rapide de la résistance aux fongicides en épidémiologie.
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Christovam, Rafael de Souza [UNESP]. "Assistência de ar em barra, ângulo e volume de pulverização no controle de doenças e na produtividade da cultura do trigo." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/105408.
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Com o intuito de melhorar a eficiência de controle de Blumeria graminis Tritici e Puccinia Tritici na cultura do trigo, o presente trabalho objetivou avaliar diferentes técnicas de pulverização sobre os depósitos, controle de oídio e ferrugem da folha, bem como sobre a produtividade da cultura. Oito experimentos foram conduzidos na área experimental da FCA/UNESP – Campus de Botucatu, na cultura do trigo (cultivar IAC-370), sendo divididos em duas fases: quatro na área didática do Departamento de Produção Vegetal – Agricultura (Fase I) e quatro na área cascalheira (Fase II) na safra agrícola de 2009. O experimento 1 foi conduzido no delineamento em blocos ao acaso com 6 tratamentos e quatro repetições, totalizando 24 parcelas. Os tratamentos foram distribuídos no esquema fatorial 3 x 2 (três níveis de ar: 0, 15 e 29 km h-1 combinados a dois volumes de pulverização: 100 L ha-1 com pontas de jato plano XR 110015 e 200 L ha-1 com pontas de jato plano XR 11003). As parcelas foram dimensionadas em 8,0 x 10,0 m (largura x comprimento). De cada parcela foram selecionadas, ao acaso, 20 plantas para amostragem dos depósitos da pulverização. Para avaliação dos depósitos, foi utilizada uma substância marcadora (corante Azul Brilhante) na concentração de 0,15% do volume da calda de pulverização e a quantificação dos depósitos foi por espectrofotometria. O experimento 2 foi conduzido no mesmo local e os tratamentos distribuídos no mesmo delineamento do experimento anterior, acrescido da testemunha (plantas não tratadas). Nos estádios de desenvolvimento 32 (segundo nó visível) e 45 (emborrachamento completo) foram realizadas pulverizações com um fungicida triazol 2 (tebuconazole) à 100 e 200 L ha-1. A severidade das doenças oídio e ferrugem da folha foram avaliadas através...
In order to improve the control efficiency of Blumeria graminis Tritici and Puccinia Tritici in wheat crop, this study aimed to evaluate different spraying techniques on spray deposits, the control of wheat powdery mildew and wheat leaf rust, as well as crop productivity. In general, eight experiments were conducted at experimental area of FCA / UNESP - Botucatu city, in the wheat crop (IAC-370 variety) being divided into two steps: four experiments were carried out at experimental area of Plant Production - Agriculture Department (Step I) and others four experiments were performed at experimental area entitled Cascalheira (Step II) during 2009 season. The first experiment was carried out in randomized blocks with six treatments and four replications, totaling 24 plots. The treatments were arranged in a factorial scheme 3 x 2 (three air speed levels: 0, 15 and 29 km h-1 combined with two spray volumes 100 L ha-1 produced by flat fan nozzle XR 110 015 and 200 L ha-1 produced by flat fan nozzle XR 11003. The plots were dimensioned with 8.0 x 10.0 m (width x length). For each plot, it was selected 20 plants at random, which these plants were utilized to quantify spray deposits. For spray deposits evaluation, it was used a tracer substance (Brilliant Blue dye) in the 0.15% of spray volume concentration and the spray deposits quantification was made by spectrophotometer. The second experiment was carried out at the same place and the treatments were arranged in the same design from the previous experiment, plus a control treatment (untreated plants). In the growth stages 32 (second visible node) and stage 45 (complete boot), it was sprayed a triazol fungicide (tebuconazole) with... (Complete abstract click electronic access below)
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Silva, Flávio Nunes da. "Retenção foliar de mancozebe com adjuvantes e taxas de aplicação no controle da ferrugem da soja /." Botucatu, 2020. http://hdl.handle.net/11449/192368.
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Orientador: Carlos Gilberto RaetanoResumo: Fungicidas multi-sítio, a exemplo do mancozebe tem sido cada vez mais utilizados no controle da ferrugem da soja (Phakopsora pachyrhizi) e como estratégia anti-resistência aos fungicidas de sítio de ação único, amplamente utilizados na agricultura. Dessa maneira, buscou-se entender como a tecnologia de aplicação por meio da redução da taxa de aplicação e pelo uso de adjuvantes podem influenciar no controle da doença causada por Phakopsora pachyrhizi, quando associada ao fungicida mancozebe. Para isso, no capitulo 1, o objetivo foi avaliar a retenção foliar do fungicida de contato mancozebe em diferentes formulações na interação com adjuvantes em folhas de soja. No capítulo 2, o objetivo foi avaliar o controle da ferrugem da soja sob variação da taxa de aplicação de mancozebe em mistura com adjuvantes. Para a superfície adaxial a formulação GD apresenta maiores volumes de líquido retido enquanto que para a superfície abaxial, em geral, a formulação não apresenta interferência significativa. No geral, maior retenção da calda foi constatada na superfície abaxial do folíolo de soja, com destaque para caldas fungicidas contendo o polímero natural J-S e o óleo mineral Argenfrut. A redução da taxa de aplicação para 50 L ha-1 e a associação do fungicida mancozebe com adjuvantes pode influenciar a severidade da ferrugem da soja, contudo, de maneira geral, se considerar apenas a redução da taxa de aplicação, de 120 L ha-1 para 50 L ha-1, não há interferência no controle da doença, prin... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Multi-site fungicides as mancozebe has been increasingly used to control soybean rust (Phakopsora pachyrhizi) and as an anti-resistance strategy to single-site fungicides, widely used on agriculture. Thus, this study aimed a better understanding on how the application technology through the reduction of application rate and the use of adjuvants can influence on the control of the disease caused by Phakopsora pachyrhizi, in association with the fungicide mancozeb. To do so, on chapter 1 the study aimed to evaluate the foliar retention of mancozeb fungicide, in the WP and WG formulations, mixed with adjuvants on soybean leaves. On chapter 2, the aim of this study was to evaluate the soybean rust control under different volume rates of mancozeb spraying mixed with adjuvants. On the adaxial surface, the WG formulation has higher volumes of liquid retained while for the abaxial surface, in general, the formulation does not present significant interference. In most cases, greater retention of the spray mixture was found on the abaxial surface of the soybean leaflet, with emphasis on those containing the natural polymer J-S and the mineral oil Argenfrut. The reduction of the application rate to 50 L ha-1 and the association of the fungicide mancozebe with adjuvants can influence the severity of soybean rust, however, in general, if we consider only the reduction of the application rate, of 120 L ha-1 to 50 L ha-1, there is no interference in disease control, especially in early stag... (Complete abstract click electronic access below)
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Wood, Henry M. "The genetic basis of prochloraz resistance in the cereal eyespots pathogen Tapesia yallundae." Thesis, University of Nottingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268501.
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Brown, M. C. "Carbendazim resistance in the eyespot pathogen Pseudocercosporella herpotrichoides." Thesis, University of Manchester, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374528.
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Banting, L. "Synthesis and evaluation of perhydroimidazolo[3,4-a]pyridines as fungicides." Thesis, University of Portsmouth, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355127.
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Oliver, Charlotte. "Phylogeny, histological observation, and in vitro fungicide screening and field trials of multiple Colletotrichum species, the causal agents of grape ripe rot." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/99418.
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Colletotrichum acutatum and C. gloeosporioides are fungal plant pathogens that have a global distribution, extensive host range, and convoluted taxonomy. Both species can cause grape ripe rot and are considered endemic to Virginia US. In 2012, C. acutatum and C. gloeosporioides were reclassified into species complexes that consist of 31 and 22 accepted species, respectively. The objectives of this study were to: 1) survey Virginia vineyards for grape ripe rot, and morphologically and phylogenetically identify isolates to the species within the complexes, 2) conduct an in vitro fungicide assay to screen fifteen commercial fungicides and combinations of two fungicides for efficacy to control isolates from seven Colletotrichum species from Virginia vineyards, 3) sequence gene fragments from three subunits of the SDH enzyme in the fungicide-screened isolates to observe potential resistance mutations, 4) investigate the susceptibility of three grapevine tissues to Colletotrichum species, 5) observe potential infection structures before and after the application of fungicides, 6) evaluate the efficacy of commercial fungicide controls of grape ripe rot in the field, and determine the most advantageous timing of applications. In my studies, I identified six Colletotrichum species: C. aenigma, C. conoides, C. fioriniae, C. gloeosporioides, C. kahawae, and C. nymphaeae. I also found two additional groups; an isolate similar to C. limetticola and C. melonis and a group of isolates that are similar to C. alienum, C. fructicola, and C. nupharicola. I also identified captan, and mancozeb as two potential active ingredients for control of grape ripe rot isolates from Virginia via the in vitro fungicide assay. Additionally, I found that combinations of two active ingredients could increase the efficacy of benzovindiflupyr, copper, and polyoxin-D. C. fioriniae germination and production of melanized appressoria was documented on leaves. I observed appressorium formation with isolates of two C. fructicola-like genotypes and C. nymphaeae, as well as secondary conidiation with isolates of C. aenigma, C. fructicola-like genotype 3, and C. nymphaeae on blooms. And finally, benzovindiflupyr, cyprodinil + fludioxonil pre-mix, and potassium phosphite + tebuconazole were identified as candidates for chemical control for grape ripe rot in the field.PHD
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Snowdon, Philip J. "The cause of fruit flavour differences associated with the fungicide prochloraz." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/843276/.
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Commercial development of the fungicide prochloraz for the control of pre- and post-harvest diseases in fruit crops has been restricted by the occasional occurrence of 'musty' taints. The primary aims of this research were to identify the cause of taint and and its means of formation. Sensitive and selective residue methodology based upon determination by gas chromatography with mass selective detection was devised, validated and used to establish 2,4,6-trichloroanisole (2,4,6-TCA) as the direct cause of taint by analysis of field-treated samples and studies involving 14C-radiolabelled prochloraz. Evaluation of analytical results in conjunction with corresponding sensory data led to proposals of flavour threshold levels ranging between 0.04 and 1.0mug/kg for 2,4,6-TCA in different fruit types. Formation of the anisole in pre-harvest treatment situations was shown to proceed via the minor plant metabolite 2,4,6-trichlorophenol (2,4,6-TCP) as the direct precursor; under post-harvest conditions, however, metabolism of prochloraz was minimal, and 2,4,6-TCA taints arose primarily from 2,4,6-TCP as an impurity (measured at 0.9% w/w) in the commercial emulsifiable concentrate formulation. Detailed investigation of the relationship between 2,4,6-TCP and 2,4,6-TCA under controlled conditions demonstrated that certain fruit types possess a capacity for direct O-methylation of the phenol to the anisole, whereas others do not. These findings were generally consistent with occurrences of taints associated with prochloraz. Kinetic studies of the active O-methyltransferase system in apple homogenates indicated the same Vmax value for 2-chlorophenol, 2,4-dichlorophenol, 2,6-dichlorophenol and 2,4,6-TCP. Reactivity in this series was found to be closely related to the ability of the molecules to to form effective nucleophiles for reaction with s-adenosylmethionine as the assumed methyl donor, and a linear relationship was established between chlorophenol pKa and log(apparent Km). The O-methylation of 2,4,6-TCP, whilst inhibited competitively by other o-chlorophenolic substrates, remained unaffected by the addition of representative plant o-diphenolics previously reported as substrates for O-methylation in plants.
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Lee, Susannah. "Mode of action of quinoxyfen, a fungicide specific to powdery mildew." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442829.
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McCartney, Cliodhna. "Fungicide resistance in Mycosphaerella graminicola and Rhynchosporium secalis in Northern Ireland." Thesis, Queen's University Belfast, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437472.
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Ruske, Rachel. "Effects of strobilurin fungicide programmes on the quality of winter wheat." Thesis, University of Reading, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288140.
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Ntushelo, Khayalethu. "Comparative studies on genetic variability and fungicide resistance in Tapesia yallundae." Thesis, Stellenbosch : Stellenbosch University, 1998. http://hdl.handle.net/10019.1/55834.
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Thesis (MScAgric)--Stellenbosch University, 1998.ENGLISH ABSTRACT: Eyespot is an important disease of spring wheat (Triticum aestivum L.). Four species of Ramulispora are associated with this disease, of which Tapesia yallundae and T. acuformis. are common. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance in Tapesia yallundae. Each of the chapters treats specific but related topics. T. yallundae, which is the only species thus far reported from South Africa, has been associated with yield losses of up to 50%. To enable the implementation of more accurate and effective control measures, understanding the dynamics of reproduction and the genetics of the pathogen is of utmost importance. Of the many plant disease control measures such as cultural practices, sanitation, biological control, etc., fungicide application is the most commonly resorted to measure in eyespot control. This thesis investigates the broader subjects of genetic variability, reproductive dynamics and fungicide resistance of Tapesia yallzll7dae. Fungicide application, however, is not without problems. The pathogen can build up resistance to fungicides. The most commonly used fungicides in eyespot control include the benzimidazole carbendazim, triazoles such as flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol, fenbuconazole, triademinol, and the imidazole, prochloraz. Cases of resistance to the groups listed above have been reported. Frequent monitoring for resistance is thus crucial to prevent wastage of fungicide and unnecessary impregnantation of the environment with potentially ineffective chemicals. In chapter 2 of this thesis 300 isolates of T. yallundae from 15 fields were evaluated for resistance against carbendazim, flusilazole, tebuconazole, propiconazole, bromuconazole, flutriafol and fenbuconazole. These results indicated that to some triazoles, such as fenbuconazole, a high level of resistance was already present in field populations. In a sexually reproducing fungus such as T. yallundae, knowledge pertaining to its ability to pass resistance factors to offspring is equally important. Mating studies were, therefore, also conducted with parental strains that showed signs of triazole resistance. Three generations were subsequently tested for resistance to five triazoles, namely flusilazole, tebuconazole, propiconazole, bromuconazole and flutriafol. Results of this study showed variable sensitivity in progeny, which indicated quantitative inheritance of resistance to triazoles. Although the sexual stage has not yet been observed in the field in South Africa, this knowledge lays the foundation for the long-term understanding of the population dynamics of the fungus. The ability of a heterothallic ascomycete population to reproduce sexually is dependent on the availability of its two mating types, MATI-I and MATI-2, their distribution, and female fertility amongst other factors. In the UK. the teleomorph is commonly observed in the field, which is in contrast to the situation in South Africa, where it has only been induced in the laboratory. A comparative study between the South African and the UK. populations was therefore undertaken. Isolates representative of the two populations were mated with tester strains as both sperm recipients and as sperm donors. This allowed the percentage of hermaphrodites to be determined. No difference in terms of female fertility was observed between the South African and the UK. populations, with both populations showing low effective population numbers. These data suggested, therefore, that the teleomorph would also occur more frequently in South Africa if the climate was more indusive to its development. The overall results of this study indicated that eyes pot could still be controlled by means of fungicide application in South Africa. Although a shift in sensitivity was observed towards fenbuconazole and flusilazole, no resistance was detected towards carbendazim. The latter might be due to the absen<.:eof the sexual stage in the field, coupled by the monocyclic nature of the pathogen and sensible fungicide regimes. The absence of T. acujormis makes the disease situation less complicated in terms of fungicide application and management. Continuous surveys will have to be conducted, however, to monitor this situation in future.
AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die genetiese variasie, reproduksie dinamika en fungisied weerstand in Tapesia yallundae. Elke hoofstuk handel oor spesifieke maar verwante onderwerpe. Oogvlek is 'n belangrike siekte van lentekoring (Triticum aestivum L.). Vier spesies van Ramulispora word geassosieer met die siekte, waarvan Tapesia yallundae en T. acuformis mees algemeen voorkom. T. yallundae, wat tans die enigste spesie is wat in Suid-Afrika aangeteken is, het al verliese van tot 50% veroorsaak. Om meer akkurate en effektiewe beheermaatreels te implementeer, is dit noodsaaklik om die oorlewingsdinamika van die patogeen te verstaan. Van al die siektebeheermaatreels soos kulturele praktyke, sanitasie, biologiese beheer ens., bly fungisiedbehandeling die mees algemene maatreel vir die beheer van oogvlek. Fungisiedtoediening het egter ook verskeie probleme. Die patogeen kan weerstand opbou teen die fungisied. Die mees algemene fungisiedes wat vir oogvlekbeheer aangewend word sluit onder meer die benzimidasool karbendazim in, triasole soos flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol, fenbukonasool, triadimenol, en die imidasool, prochloraz. Weerstand is egter reeds teen hierdie middels bekend. Gedurige monitering vir weerstand is dus krities om die vermorsing van fungisied en besoedeling van die omgewing met oneffektiewe middels te beperk. In hoofstuk 2 van hierdie manuskrip word 300 isolate van T. yallundae van 15 lande geevalueer vir weerstand teenoor karbendazim, flusilasool, tebukonasool, propikonasool, bromukonasool, flutriafol en fenbukonasool. Resultate dui daarop dat teen sommige van hierdie triasole, soos bv. fenbukonasool, daar reeds 'n hoe vlak van weerstand teenwoordig was in veldpopulasies. In 'n seksueel reproduserende fungus soos T. yalluJ1dae, is dit noodsaaklik om te bepaal wat sy vermoe is om weerstandbiedenheid aan die nageslag oor te dra. Om die rede is paringstudies ook op ouers wat tekens van weerstand teenoor triasole getoon het uitgevoer. Drie generasies was gevolglik getoets vir weerstand teenoor vyf triasole, naamlik flusilasool, tebuconasool, propikonasool, brumukonasool en flutriafol. Resultate van die studie het 'n variasie in sensitiwiteit van die nageslag getoon, wat op 'n kwantitatiewe oorerwing van weerstand teen £riasole dui. Alhoewel die teleomorf nog nie in lande in Suid-Afrika opgemerk is nie, Ie hierdie kennis die fondament vir die langtermyn vertolking van die populasie dinamika van hierdie fungus. Die vermoe van 'n heterotalliese askomiseet populasie om seksueel voort te plant is afhanklik van die beskikbaarheid van sy twee paringstipes, MATI-I en MATl-2, hul verpreiding, vroulike vrugbaarheid en ander faktore. Alhoewel die teleomorf algemeen in lande in die Verenigde Koninkryk opgemerk word, is dit in kontras met die situasie in Suid-Afrika, waar hierdie stadium nog slegs in die laboratorium gelnduseer kon word. 'n Studie is dus onderneem om die Suid-Afrikaanse en V.K. populasies met mekaar te vergelyk. Isolate van die twee populasies is dus gepaar met paringsisolate as beide sperm ontvangers en sperm donors. Hierdie prosedure het dit moontlik gemaak om die persentasie hermafrodiete te bepaal. Geen verskille in vroulike fertiliteit is tussen die Suid-Afrikaanse en V.K. populasies bespeur nie, en beide populasies het ook 'n lae effektiewe populasie getal getoon. Hierdie data het dus voorgestel dat die teleomorf ook meer algemeen in Suid-Afrika sou voorkom as die klimaat meer geskik was vir teleomorf vormmg. Die resultate van hierdie studie het tot die slotsom gelei dat oogvlek steeds deur fungisiedbehandeling in Suid-Afrika beheer kan word. Alhoewel daar 'n merkbare verskuiwing in sensitiwiteit teenoor fenbukonasool en flusilasool was, was geen weerstand teenoor karbendazim waargeneem nie. Laasgenoemde kan dalk toegeskryf word aan die afwesigheid van die teleomorf in die veld, gekombineer met die monosikliese natuur van die patogeen en gebruik van alternerende fungisiedes. Die afwesigheid van T. acuformis maak die plaaslike siektetoestand minder gekompliseerd in terme van fungisied aanwending en bestuur. Voortdurende opnames sal egter uitgevoer moet word om hierdie situasie ook in die toekoms te monitor.
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Jensen, Mari N. "UA Licenses Patent for Natural Fungicide: Natural Product Fights Plant Diseases." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2005. http://hdl.handle.net/10150/622198.
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Way, John Alexander. "Investigating a microbial fungicide to enhance biological control of plant disease." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/843864/.
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The antibiotic, 2,4-diacetylphloroglucinol (Phl), is produced by a range of naturally isolated fluorescent pseudomonads, found in disease suppressive soils. The natural isolate, P. fluorescens F113, protects pea plants from the pathogenic fungus, Pythium ultimum, by reducing the number of pathogenic lesions on the plant's roots. This beneficial effect was however, outweighed by the F113 causing an overall reduction in the emergence of the pea plants in the infected soil. The gene locus responsible for the Phl production was shown to be functionally conserved between the P. fluorescens F113 and another Phl producing organism, P. fluorescens Q2-87. Following identification of this functional sequence homology, the genes were isolated from F113, by optimised, long PCR. The 6.7-kb gene cluster was inserted into the chromosome of a non-pathogenic P. fluorescens, SBW25, which can effect biological control against the plant pathogen, Pythium ultimum through competitive exclusion of the fungus, by means of its strong colonising competence. The insertion was a targeted, homologous recombination designed to insert the Phl coding genes, from the F113, into a non-essential, lacZY coding region of the SBW25 chromosome. The transformed strains of SBW25 assumed two different morphological appearances. The morphological changes were noted at a ratio of 1:1 of normal morphology and altered morphology. Transformation of SBW25 with the Phl locus without this repressor element led to transformants with only normal morphology. All transformants were able to suppress P. ultimum through antibiotic production following the Phl transformation. However, the fitness of the transformants was reduced in flask culture, at 30°C, against the un-transformed SBW25. The organisms transformed with the entire Phl locus were seen to clump together in the culture media. The strain transformed with the Phl locus lacking the repressor element behaved normally. When inoculated on pea seedlings, the strain containing no repressor element behaved similarly to the F113, causing lower pea seed emergence. A transformant containing the entire Phl genetic locus had not lost its environmental competence on the pea roots, maintaining a high population, but was unable to maintain a high population in the surrounding soil.