Les oomycètes représentent un groupe d’organismes très diversifiés responsables de diverses maladies d’animaux et de plantes. En agriculture le mildiou de la pomme de terre, causé par un oomycète phytopathogène, occasionne à lui seul des pertes économiques mondiales annuelles de 3 à 5 milliards de dollars américains. La lutte contre le mildiou de la pomme de terre et de la laitue, causés respectivement par, Phytophthora infestans et Bremia lactucae, repose en grande partie sur l’utilisation de fongicides. Cependant, l’apparition de nouvelles souches résistantes au métalaxyl a réduit de manière substantielle l’efficacité des fongicides de synthèse. De plus, les fongicides doivent être appliqués au moment opportun pour être efficaces contre le mildiou. L’approche par modélisation constitue donc une option intéressante pour améliorer la lutte contre les mildious en offrant la possibilité de prédire les périodes à risque et d’améliorer la régie d’application des fongicides. Toutefois, l’évaluation de ces modèles a montré qu’ils manquent de précision et que leur efficacité varie d’une année à l’autre. Ce manque de précision peut s’expliquer en partie par l’absence de considération de la présence ou de l’abondance de l’inoculum aérien. P. infestans et B. lactucae produisent un inoculum adapté à la dispersion aérienne. Cependant, il existe un manque de connaissance notable dans la littérature sur l’aérobiologie de ces deux oomycètes phytopathogènes. Un modèle de simulation dynamique qui intègrerait l’information sur l’aérobiologie de l’agent pathogène permettrait de prédire plus efficacement les périodes de risque d’infection par le mildiou. Ainsi, l’objectif général de ce projet de doctorat était d’améliorer la connaissance sur l’aérobiologie de deux oomycètes (P. infestans et B. lactucae) dans l’optique de mieux comprendre et prédire les périodes d’infection du mildiou de la pomme de terre et de la laitue. Dans un premier temps, la distribution spatiotemporelle des spores à l’échelle d’une région de production de monoculture de pommes de terre a été déterminée. Les résultats ont montré que la distribution des spores est hétérogène et l’efficacité des mesures prophylactiques peut être évaluée à l’aide de l’aire sous la courbe de progression de l’inoculum aérien. De plus, l’information dérivée de l’implantation d’un réseau de capteur permet de pondérer le risque d’infection estimé par les modèles prévisionnels. Dans un deuxième temps, la relation entre la concentration aérienne de spores et l’intensité du mildiou a été établie. Cette relation a permis de définir des seuils d’intervention basés sur la concentration aérienne de spores. Dans le pathosystème de la pomme de terre, le seuil d’intervention varie en fonction des lignées clonales de P. infestans alors que dans celui de la laitue, ce seuil ne tient pas compte des lignées clonales de B. lactucae. Un outil moléculaire pour le comptage des spores a été développé pour pallier aux inconvénients liés à la quantification des spores au microscope. Les résultats de cette étude ont montré, entre autres, que sous conditions climatiques au Canada deux heures de mouillure sont suffisantes pour l’établissement d’une infection par B. lactucae, contrairement aux trois à quatre heures de mouillure proposées dans la littérature. Dans un troisième temps, un modèle de simulation de la concentration aérienne des spores a été développé. La relation entre le nombre de spores observées à l’heure et le nombre de spores prédit à l’heure est linéaire. Dans plus de 94% des cas, les coefficients de détermination de la régression entre le nombre de spores observées et celui prédit sont supérieurs à 0,7. Même si ce modèle est une première dans la littérature publiée et représente une avancée significative dans l’aérobiologie des oomycètes, il est à améliorer notamment dans l’optique de pouvoir développer un modèle générique comme outil de recherche pour l’étude de l’aérobiologie des oomycètes phytopathogènes. En effet, l’étape à venir sera d’incorporer ce modèle comme module dans un système de support décisionnel pour prédire efficacement l’apparition des symptômes de mildiou. Les auteurs espèrent que ce modèle constituera la base pour le développement d’un modèle générique pour tous les oomycètes phytopathogènes à dispersion aérienne.

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

<i>Phytophthora infestans</i>, the oomycete pathogen responsible for late blight of potato and tomato, is regarded as the biggest threat to global potato production and is thought to cost the industry around £6 billion annually. Traditionally, fungicides have been used to control the disease, but this is both economically and environmentally costly, as multiple chemical applications may be required during a single growing season. <i>P. infestans</i> has rapidly overcome genetic resistances introduced into cultivated potato from wild species. This provides the rationale for developing artificial resistance genes to create durable resistance to late blight disease.<i>Phytophthora</i> species secrete essential effectors into plant cells that target critical host cellular mechanisms to promote disease. One such <i>P. infestans</i> effector is AVR3a^KI which is recognised by the potato R3a protein, a member of the CC-NB-LRR type resistance gene family. However, the closely related virulent form, AVR3a^EM, which is homozygous in more than 70% of wild <i>P. infestans</i> isolates, evades this recognition. Domain swapping experiments have revealed that the LRR domain of R3a is involved in recognition of AVR3a^KI, as the CC-NB domain of an R3a-paralog which does not mediate recognition of AVR3a^KI, is able to induce a HR when combined with the LRR of wild-type R3a. However, a chimeric protein consisting of the CC-NB domain of a more distantly-related homolog of R3a and the LRR of domain of R3a, is unable to recognise AVR3a^KI, suggesting that function is achieved only when the different domains of an R protein are attuned to recognition and signalling. Gain-of-function variants of <i>R3a</i> (<i>R3a*</i>), engineered by an iterative process of error-prone PCR, DNA fragmentation, re-assembly of the leucine rich repeat (LRR)-encoding region of <i>R3a</i>, are able to recognise both forms of AVR3a. This gain-of-recognition is accompanied by a gain-of-mechanism, as shown by a cellular re-localisation from the cytoplasm to prevacuolar compartments upon perception of recognised effector forms. However, R3a* variants do not confer resistance to AVR3a^EM-carrying isolates of <i>P. infestans</i>.Future efforts will target the NB-ARC domain of R3a, in a bid to fine-tune the intra-cellular signalling of gain-of-recognition R3a* variants. It is hoped that a shuffled <i>R3a*</i> gene, capable of conferring resistance to <i>P. infestans</i> isolates harbouring AVR3a^EM, will provide durable late blight resistance when deployed in the field in combination with other mechanistically different R proteins.

In this thesis, I set out to investigate the nature of nonhost resistance responses of Nicotianae sylvestris against Phytophthora capsici and P. infestans. Schulze-Lefert and Panstruga (2011) proposed that the inability of a pathogen to establish infection in nonhost plants could be a feature of the phylogenetic distance between host and nonhost plants. In distantly related plants PAMP triggered immunity is thought to be the major contribution to resistance as effectors are inappropriately attuned to perturb their orthologous plant targets. In contrast, effector triggered immunity (ETI) could be the major contributor to resistance in nonhost plants that are more closely related to the host plants. P. capsici and P. infestans can both infect Solanaceae plants including Solanum lycopersicum and N. benthamiana but both fail to cause disease or complete their life-cycle in N. sylvestris. Based on the hypothesis of Schulze-Lefert and Panstruga (2011), ETI should be contributing towards effective nonhost resistance responses in N. sylvestris against both pathogens. In addition, it is tempting to speculate that N. sylvestris, with a limited availability of functional resistance genes including Nucleotid binding-Leucine rich repeats (NB-LRRs), could be setup to recognise and responds to sequence-related effectors from P. infestans and P. capsici, rather than to have resistance genes that are specifically attuned to either pathogen. I conducted three research strands to test this theory. In Chapter 3 I used MCL clustering to classify 563 P. infestans and 515 P. capsici RXLR effector genes and defined families on the basis of sequence similarity. I found that the P. infestans and P. capsici RXLR complements are mostly species-specific. To investigate the role of ETI in nonhost resistance, 48 P. capsici and 82 P. infestans RXLR were screened for recognition by the nonhost plant N. sylvestris. Using this approach I identified 4 P. infestans and 8 P. capsici effectors that are consistently recognised in N. sylvestris (Chapter 4). Surprisingly, most of the recognised effectors are part of species-specific clusters. In Chapter 5 I established and implemented PathSeq, an enrichment and sequencing tool that facilitates the massively parallel study of naturally occurring diversity of pathogen effectors, including those that are recognised in N. sylvestris. In the same chapter I also used PathSeq and de novo prediction to expand the P. infestans RXLR complement from 563 to 1220 putative effectors. In this thesis I have shown that P. infestans and P. capsici effector set are diversifying at the sequence level. My data also suggests that ETI might play a part in nonhost resistance of N. sylvestris to P. capsici and P. infestans. Finally I have presented PathSeq, a tool that allows the study of the effectors set in multiple isolates at the time, and this, for a fraction of the cost of a full genome sequencing experiment.

<p>Oomycetes have long been considered as a separate class within the kingdom Fungi, but they are in fact closer to brown algae. They are currently classified in the Stramenopile eukaryotic kingdom, which includes heterokont algae and water molds. The major cell wall polysaccharides in Oomycetes are b-(1à3) and b-(1à6)-glucans, as well as cellulose, which has never been reported in any fungal species. Chitin - the major cell wall polysaccharide in fungi - occurs in minor amounts in the walls of some Oomycetes. Some Oomycete species are pathogens of great economical importance. For example, species of the genus <em>Phytophthora </em>are well studied plant pathogens that cause considerable economical losses in agriculture. Saprolegniosis, a fish disease caused by species from the genus <em>Saprolegnia</em>, is a major problem in the aquaculture industry and represents a threat to populations of salmonids in natural habitats. Currently, there are no chemicals available that are at the same time efficient Oomycete inhibitors, environmentally friendly and safe for human consumption of treated fishes. The biosynthesis of cellulose in Oomycetes is poorly understood, even though this biochemical pathway represents a potential target for new Oomycete inhibitors. In this work, cellulose biosynthesis was investigated in two selected Oomycetes, the plant pathogen <em>Phytophthora infestans</em> and the fish pathogen <em>Saprolegnia monoica</em>.</p><p> </p><p>A new Oomycete <em>CesA</em> gene family was identified. It contains four homologues designated as <em>CesA1, CesA2, CesA3</em> and <em>CesA4</em>. The gene products of <em>CesA1, 2</em> and <em>4 </em>contain Pleckstrin Homology domains located at the N-terminus. This represents a novel feature, unique to the Oomycete <em>CesA </em>genes. <em>CesA3</em> is the dominantly expressed <em>CesA </em>homologue in the mycelium of both <em>S. monoica</em> and <em>P. infestans</em>, while <em>CesA1</em> and<em> CesA2</em> are up-regulated in virulent life stages of <em>P. infestans</em>. <em>CesA4</em> was expressed only in minute amounts in all investigated types of cells. Gene silencing by RNA interference of the whole <em>CesA</em> gene family in <em>P. infestans</em> lead to decreased amounts of cellulose in the cell wall. The inhibitors of cellulose synthesis DCB and Congo Red had an up-regulating effect on <em>SmCesA</em> gene expression, which was accompanied by an increased b-glucan synthase activity <em>in vitro</em>. In addition, these inhibitors slowed down the growth of the mycelium from <em>S. monoica</em>. Zoospores from <em>P. infestans</em> treated with DCB were unable to infect potato leaves and showed aberrant cell wall morphologies similar to those obtained by silencing the <em>CesA</em> gene family.</p><p>Altogether these results show that at least some of the <em>CesA1-4</em> genes are involved in cellulose biosynthesis and that the synthesis of cellulose is crucial for infection of potato by <em>P. infestans</em>.</p><p> </p>

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2007. / Härtill 5 uppsatser.

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-04-20T13:00:17Z No. of bitstreams: 1 texto completo.pdf: 327861 bytes, checksum: 10b3c4ac9c1fb002cc94c4da4da28d0e (MD5) / Made available in DSpace on 2017-04-20T13:00:17Z (GMT). No. of bitstreams: 1 texto completo.pdf: 327861 bytes, checksum: 10b3c4ac9c1fb002cc94c4da4da28d0e (MD5) Previous issue date: 2002-12-03 / Fundação de Amparo à Pesquisa do Estado de Minas Gerais / A busca de alimentos produzidos sob um sistema de manejo menos agressivo ao meio ambiente vem sendo adotado por um número cada vez maior de produtores. Entretanto, apesar de existirem diversos benefícios na redução ou até eliminação do uso de defensivos, a grande diversidade de doenças em tomateiro (Lycopersicon esculentum Mill.), capazes de limitar a produção, torna necessária a busca por alternativas viáveis, eficientes e tecnicamente comprovadas. Dentre os organismos mais estudados, bactérias têm sido relatadas como agentes de biocontrole capazes de atuar por meio de mecanismos como antibiose, parasitismo, competição e indução de resistência. O presente trabalho teve como objetivos selecionar bactérias do filoplano do tomateiro, baseado em uma estratégia de seleção in vivo, verificando se há um método de isolamento que permita obter antagonistas eficientes no controle da pinta-preta, causada por Alternaria solani, requeima por Phytophthora infestans, mancha-bacteriana pequena por Pseudomonas syringae pv. tomato e mancha-bacteriana por Xanthomonas vesicatoria. Objetivou ainda estudar a possibilidade dos mecanismos de antibiose e indução de resistência serem responsáveis pelo controle destas doenças e se testes de antibiose in vitro são adequados como critério de seleção. Caracterizar aspectos biológicos dos antagonistas que podem otimizar sua aplicação como agente de biocontrole. Determinar a quais produtos antimicrobianos os isolados são insensíveis, visando fornecer subsídios para o desenvolvimento de meios semi-seletivos e estudos de dinâmica populacional. Verificar sua compatibilidade com antibióticos e fungicidas registrados para o controle de enfermidades do tomateiro, a fim de inseri-lo no sistema de manejo integrado e estudar a eficiência de antagonistas selecionados em condições de campo. Os resultados demonstram que, em folíolos mais jovens, os métodos de isolamento que visam obter bactérias da população total e da superfície do filoplano, foram os que permitiram obter a maioria dos antagonistas. O único obtido de folíolos mais velhos foi proveniente da população capaz de habitar sítios protegidos do filoplano e/ou resistir a fatores de estresse. Não se observou relação entre características biológicas dos antagonistas e dos patógenos testados. Nos testes de antibiose com os antagonistas selecionados, o isolado UFV-STB 6 foi capaz de produzir compostos voláteis e inibir a germinação de cistos de Phytophthora infestans, o que possivelmente deve estar envolvido no controle da requeima. O isolado UFV-IEA 6 produziu quitinase, havendo uma tendência em reduzir a taxa de crescimento de Alternaria solani por compostos voláteis. Ficou demonstrado que os testes de antibiose in vitro são inadequados como critério para seleção de agentes de biocontrole do filoplano de tomateiro. A caracterização dos melhores antagonistas demonstrou que três são bactérias Gram-positivas, em forma de bastonete, e uma Gram-negativa, pleiomórfica. Dentre as Gram-positivas todas são anaeróbias facultativas e uma forma endósporos. Nenhum antagonista foi capaz de causar reação de hipersensibilidade (HR) em fumo e produzir pigmento fluorescente in vitro. Os períodos de geração calculados a partir das curvas de crescimento revelaram que três isolados são capazes de se multiplicar rapidamente em meio de cultura, o que é uma característica desejável. Os resultados obtidos a partir dos antibiogramas, mostraram que existem antibióticos que podem ser utilizados para elaboração de meios semi-seletivos, adequados a cada antagonista e os testes de compatibilidade com antibióticos e fungicidas utilizados na cultura do tomateiro revelaram que os antagonistas podem ser expostos aos fungicidas benomyl, enxofre, dimetomorph e tiofanato-metílico. Verificou-se também a inadequação de se utilizarem compostos antimicrobianos em meio de cultura para isolamento de agentes bacterianos de controle biológico, uma vez que os antagonistas selecionados foram sensíveis à maioria dos produtos testados. Os testes com as enzimas indicadoras do estado de indução de resistência, β-1,3-glucanases, Fenilalanina amônia-liase (PAL), Peroxidases (PO), Polifenoloxidases (PPO) e Lipoxigenases (LOX), indicaram que o isolado UFV-IEA 6 foi capaz de promover aumento significativo na atividade das PO, evidenciando a possibilidade do antagonista agir como indutor de resistência. Esse parece ser o primeiro caso que se tem conhecimento de uma bactéria não fitopatogênica do filoplano induzindo resistência na mesma cultura de onde foi obtida. Os testes com os dois antagonistas em condições de campo demonstraram que UFV-STB 6 foi o mais eficiente em reduzir a severidade da requeima no terços médio e superior das plantas, enquanto UFV-IEA 6, somente no terço superior. Houve tendência na redução do progresso da septoriose por UFV-STB 6 e capacidade em diminuir o número de frutos com sintomas de requeima. Os resultados demonstram o potencial de uso dos agentes de biocontrole selecionados para as doenças da parte aérea de tomateiro estudadas. / Farmers are increasingly adapting environmentally less aggressive management systems for food production and there are many benefits in reducing or even eliminating pesticide use. Due to a large number of production limiting diseases on tomato (Lycopersicon esculentum), it is desirable to find technically viable and proven alternatives for their control. Among the microorganisms, bacteria have been reported as biocontrol agents capable of acting through antibiosis, parasitism, competition and induced resistance. The present study aimed at selecting the tomato phylloplane bacteria, based on in vivo isolation strategy, and to determine if this method permits obtaining efficient antagonists to control Alternaria solani leaf spot, Phytophthora infestans blight, small bacterial leaf spot caused by Pseudomonas syringe pv tomato, and bacterial leaf spot caused by Xanthomonas vesicatoria. The study also aimed at determining mechanisms of action, such as antibiosis and induced resistance, involved in disease control, and to determine if the antibiosis tests are sufficient selection criteria. The study also included biological characterization of the antagonists that may optimize their use. To help develop selective or semi-selective media for population dynamic studies, insensitivity of selected isolates to some antimicrobial compounds was also determined. The compatibility of select antagonists with antibiotics and fungicides registered for control of tomato diseases was elucidated so that the antagonist can be inserted in the integrated management. Field studies were done to determine the efficiency of select antagonists. The isolation method that obtain total bacterial population from the phylloplane of the young leaflets permitted obtaining maximum number of antagonists. The only one isolate obtained from the older leaflets originated from the population capable of inhabiting protected sites of phylloplane and/or that resist stress factors. There was no relation between biological characteristics of the antagonists and of the pathogen tested. In the antibiosis testes, the isolate UFV-STB 6 produced volatile compounds that inhibited germination of P. infestance cyst and may be involved in the control of blight. The isolate UFV-IEA 6 produced chitinase and showed a tendency to reduce A. solani growth by the volatile compounds. In vitro antibiosis testes were inadequate criteria to select biocontrol agents from tomato phylloplane. The characterization of promising antagonists showed that three were Gram positive bacilli and one was gram negative pleiomorphic bacteria. Among the Gram positives all were facultative anaerobes and the one formed endospores. None of the antagonists caused hypersensitive reaction (HR) in tobacco, and did not produce fluorescent pigment in vitro. The generation period calculated from the growth curve revealed that three isolates are capable of multiplying rapidly in the culture media, which is a desirable characteristic. The antibiograms showed that there are antibiotics that can be used for elaboration of semi-selective media for each of antagonists and the compatibility testes with antibiotics and fungicides used on tomato crop revealed that the antagonists can be exposed to fungicides such as benomyl, sulfur, dimethomorph and thiophante-methyl. Many antimicrobial compounds were inhibitory to the selecte antagonists in culture media used for isolation of bacterial biocontrol agents, therefore were inadequate for use in selective media. The analysis of enzymes involved in induced resistance, like -1,3-gluconase, phenylalanine ammonia lyase (PAL), peroxidase (PO), polyphenol oxidase (PPO) and lipoxigenase (LOX), showed that the isolate UFV-IEA 6 was capable of increasing PO activity, showing the possibility of being a resistance inducer . This appears to be the first case of a non-pathogenic phylloplane bacterium inducing resistance in a plant of origin. The field testes with two antagonists, UFV-STB 6 was more efficient in reducing the blight severity in the middle and upper third of the plant, while UFV-IEA 6 only in the upper third. The latter isolate also showed a tendency for reducing the Septoria leaf spot progress and the number of fruits with the blight symptoms. The results showed these isolates have the potential of use to control tomato diseases of aerial parts. / Tese importada do Alexandria

Submitted by Marco Antônio de Ramos Chagas (mchagas@ufv.br) on 2017-06-05T18:18:40Z No. of bitstreams: 1 texto completo.pdf: 526941 bytes, checksum: 4b11f2d8692c5b778d06c143cc4554c4 (MD5) / Made available in DSpace on 2017-06-05T18:18:40Z (GMT). No. of bitstreams: 1 texto completo.pdf: 526941 bytes, checksum: 4b11f2d8692c5b778d06c143cc4554c4 (MD5) Previous issue date: 2005-07-29 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / Foi realizado neste trabalho um cruzamento interespecífico de tomateiro entre a cultivar Santa Clara (Lycopersicon esculentum) e o acesso do Banco de Germoplasma de Hortaliças da UFV BGH 6902 (Lycopersicon hirsutum), resistente a Phytophthora infestans, responsável por causar uma das mais importantes doenças da cultura do tomateiro, requeima, para a qual não existe variedade resistente. Os genitores, as gerações F1, F2, RC1 e RC2 foram utilizados para estudar a herança da resistência a P. infestans, e estimar os parâmetros genéticos associados à resistência. Através da análise da área abaixo da curva de progresso da doença, constatou-se que a herança é do tipo poligênica e que existe dominância controlando o caráter, porém, pela análise de médias, o efeito aditivo foi o mais importante. A herdabilidade do caráter é baixa, mas existe possibilidade de selecionar indivíduos resistentes em gerações segregantes. Estudou-se também a herança de características de frutos como peso, comprimento, largura de frutos concluindo-se que a herança destas é do tipo quantitativa. A característica pilosidade de frutos é de herança monogênica e segue o padrão de segregação 3:1 (com pilosidade/sem pilosidade), com dominância completa do alelo que condiciona a presença de pilosidade nos frutos. Foi estudada a correlação existente entre a severidade de requeima e características medidas nos frutos: peso, comprimento e largura de frutos, e verificou-se que estas características não estão correlacionadas com a resistência a P. infestans. Por meio de gráfico de dispersão gerado pelo estudo de componentes principais, foi possível visualizar o comportamento das seis populações estudadas ( Santa Clara , BGH6902, F1, F2, RC1 e RC2) e identificou- se, também, que a característica peso de frutos não foi importante para a explicação da variabilidade genética estudada. Com avanço da geração F2, via SSD, conseguiram-se genótipos da população F5 que foram avaliados quanto à resistência a P. infestans. Esta resistência foi encontrada em níveis superiores à média do genitor BGH6902. Além disso, foram identificados os melhores genótipos pelo método de seleção entre e dentro de famílias, que poderão ser utilizados na continuidade deste programa de melhoramento. / Interespecific crossing between tomato cultivar 'Santa Clara' (Lycopersicon esculentum) and the access BGH 6902 (Lycopersicon hirsutum), resistant to Phytophthora infestans, causal agent of late blight, one of the most important tomato diseases, for which resistant variety doesn't exist. The parents, F1, F2, BC1 and BC2 generations were used to study the heritability of P. infestans resistance and estimate the genetics parameters. By area under the disease progress curve, it was concluded that heritage is polygenic and there is a dominance controlling the character, however, by media analysis the additive value was more important. The heritability is low, even though there is the possibility to select resistant genotypes in segregating generations. The heritage of fruit characters such as weight, length and width, was studied and it was concluded that the heritage is quantitative. Presence of trichomes have monogenic heritage and follow the pattern 3:1 of segregation (with trichomes/without trichomes), with complete dominance of the allele to trichomes presence. The correlation among late blight severity and fruit characters was studied and it was verified that there isn't correlation among these characters and late blight resistance. By graphic dispersion of principal components study, it was possible to see the behavior of the generations ('Santa Clara', BGH6902, F1, F2, BC1 e BC2) and it was identified that weight of fruits wasn't important to explain the genetic variability. Advancing generations by SSD, F5 genotypes were obtained which were evaluated for late blight resistance, and resistance in superior levels was found comparing with BGH 6902. The best genotypes by the method of within-between families selection was identified as well, which may be used in the continuity of this breeding program.

Submitted by Nathália Faria da Silva (nathaliafsilva.ufv@gmail.com) on 2017-07-07T16:54:28Z No. of bitstreams: 1 texto completo.pdf: 697730 bytes, checksum: 97e65860ffb26826b1b8a3b89981adc8 (MD5) / Made available in DSpace on 2017-07-07T16:54:28Z (GMT). No. of bitstreams: 1 texto completo.pdf: 697730 bytes, checksum: 97e65860ffb26826b1b8a3b89981adc8 (MD5) Previous issue date: 2001-03-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo deste trabalho foi avaliar o efeito da temperatura e do tempo de molhamento foliar nos componentes epidemiológicos de isolados das linhagens clonais US-1 e BR-1 de isolados de Phytophthora infestans existentes no Brasil e a validação do simulador de epidemias de requeima Blight nas condições ambientais do País. Os componentes epidemiológicos avaliados neste estudo foram o período de incubação, o período latente, o crescimento das lesões, a esporulação e a germinação dos esporângios do patógeno. Estudou-se o efeito da temperatura na germinação dos esporângios, no período de incubação, no período latente, no crescimento das lesões e na esporulação do patógeno. As linhagens clonais US-1 e BR-1 foram afetadas de maneira diferenciada pelas variações de temperatura. Os isolados de US-1 e BR-1 apresentaram maior percentual de germinação indireta em temperaturas inferiores a 15°C. O maior percentual de germinação direta foi a 22°C, em ambas as linhagens. Os menores valores de período de incubação e de período latente ocorreram a 22°C em ambas as linhagens. A essa temperatura, o período de incubação para US-1 foi de 66,7 h e, para BR-1, de 44,0 h, enquanto o período latente foi de 93,3 h para US -1 e de 68,0 h para BR-1. O crescimento das lesões também foi influenciado pela variação de temperatura entre 10 e 27°C, em ambas as linhagens clonais. Na avaliação da esporulação, em plantas de batata e tomate observou-se maior esporulação a 22°C. Na quantificação dos efeitos do binômio temperatura – tempo de molhamento foliar, a linhagem clonal BR-1 apresentou maior número de lesões no hospedeiro a 10°C com 24 horas de molhamento foliar, e a US-1, a 15°C, com o mesmo tempo de molhamento foliar. Na validação do simulador Blight, realizaram-se dois ensaios de campo, um no inverno e outro no período de primavera-verão, com a cultura da batata. Quantificou-se o progresso da doença nessas duas épocas, e com os dados climáticos coletados foram realizadas simulações. Houve boa correlação entre a epidemia observada no campo no período do inverno e a simulada. No segundo ensaio, o simulador subestimou a intensidade da doença. Para ser usado no Brasil, o simulador Blight necessitará de ajuste nas equações matemáticas que o compõem. / This study aimed at evaluating temperature and leaf-wetness period effect on the epidemiological components of clonal lines of Phytophthora infestans isolates US-1 and BR-1 present in Brazil and to validate the simulator of the late blight epidemic Blight under Brazilian environmental conditions. The isolates were affected differently by the temperature variation although maximum indirect and direct sporangial germination of both the isolates occurred at temperatures below 15°C and at 22°C, respectively. Both the isolates had the least incubation and latent period at 22°C, which was, respectively, 66.7 h and 93.3 h for US-1 and 44.0 h and 68.0 h for BR-1. In both the clonal lines, the lesion growth was also affected by the temperature variation between 10 to 27°C. The maximum sporulation on potato and tomato plants occurred at 22°C. Quantification of the combined effect of temperature and leaf-wetness period showed that the largest lesion, in 24 h, on the host was produced at 10°C by the BR-1 and at 15°C and by the US-1 lines with 24 h leaf-wetness period. The Blight simulator was validated on the winter and spring-summer season potato crop . Simulations were done by quantifying the disease progress and using the climatic data of the crop period. While there was a good correlation between the observed epidemic and the simulation in the winter planting, the simulator under- estimated the disease intensity in the spring-summer season. Therefore, the Blight simulator may require adjustments in the component mathematical equations for use in Brazil.

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-graduação em Engenharia de Produção / Made available in DSpace on 2012-10-20T21:06:49Z (GMT). No. of bitstreams: 1 225932.pdf: 1800466 bytes, checksum: 7546469656bbd6296a6ac29ff925f29e (MD5) / Este trabalho apresenta um estudo desenvolvido com dados longitudinais, usando a metodologia de modelos não lineares em curvas de crescimento, com diferentes estruturas para a matriz de covariância, fixando uma função para a parte determinística. Após a seleção da melhor matriz de covariância, foram experimentadas diferentes funções, a fim de se escolher o modelo não linear mais adequado. Este procedimento foi aplicado em dados da porcentagem de severidade da doença Late blight em quatro variedades de batata (Solanum tuberosum), causada por Phytophthora infestans. O modelo não linear selecionado foi o que usa uma das parametrizações da função de Gompertz e matriz de covariância de Simetria Composta. Os testes de hipóteses realizados sobre os parâmetros do modelo confirmaram a existência de diferença significativa entre as variedades.