Universiẗat, Diss., 2001--Mainz. / Auch als gedr. Diss.

Les facteurs d’initiation de la traduction sont des protéines de plante cruciales pour l’établissement du cycle viral des Potyvirus. Des mutations dans ces facteurs sont la source de résistances récessives chez de nombreuses plantes d’intérêt agronomique. Ces résistances peuvent être déjouées par les Potyvirus, principalement par l’acquisition de mutations dans la VPg (Viral Protein Genome-linked) permettant de rétablir une interaction compatible avec les formes mutées des facteurs eIF4E. Ce modèle simple de co-évolution n’est pas applicable au pathosystème Laitue/LMV (Lettuce mosaic virus). En effet, chez la laitue, deux allèles mo11 et mo1² du gène mo1 codant pour eIF4E confèrent la résistance au LMV. Dans ce pathosystème, la VPg n’a été associée qu’au contournement de l’allèle de résistance mo11. Un deuxième facteur de virulence entre en jeu : la protéine CI (Cylindrical Inclusion, helicase caractéristique des potyvirus), responsable du contournement des résistances mo11 et mo1². L’étude approfondie de la diversité naturelle du LMV a permis d’identifier 4 positions en acides aminés dans la CI, potentiellement impliquées dans le mécanisme de contournement. Celles-ci ont été étudiées par une approche de génétique inverse. Les résultats mettent pour la première fois en évidence l’existence d’un contournement de résistance partiel (toutes les plantes ne sont pas infectées) et graduel (la proportion de plantes infectées augmente avec le nombre de mutations). Par ailleurs, ce contournement est associé au rétablissement du mouvement en systémie du virus en contexte de résistance et est dépendant du fond génétique du virus. / Eukaryotic translation initiation factors are essential host factors required for Potyvirus infection and represent a major component of recessive resistance against potyviruses in several crops. Potyvirus adaptation to eIF4E-mediated resistance usually occurs through mutations in the VPg (Viral Protein Genome-linked), restorating its interaction with the mutated eIF4E factor. Such co-evolution model doesn’t match the Lettuce/LMV (Lettuce mosaic virus) pathosystem. Indeed, two resistance alleles mo11 and mo1² of the mo1 gene encoding eIF4E, confer resistance against LMV in lettuce. The VPg triggers virulence only towards the mo11 allele. Another virulence determinant was identified: the CI (Cylindrical inclusion, potyviral helicase), which was associated with both mo11 and mo1² overcoming. By investigating the LMV natural diversity, we identified 4 amino acid positions in the CI-Cterminus potentially involved in mo1 overcoming. Reverse genetics experiments were carried out, demonstrating that mutations at these positions are associated with a partial (not all the plants are infected) and gradual (increase with the accumulation of mutations) resistance breaking mechanism. Resistance-breaking mutations were shown to restore the systemic movement of the virus and to be influenced by the viral genetic background.

Made available in DSpace on 2014-06-11T19:35:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-05-24Bitstream added on 2014-06-13T18:45:55Z : No. of bitstreams: 1 chaves_alr_dr_botfca.pdf: 1845018 bytes, checksum: 6e354e18d8a7d6379c01e67c86d71ad8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Secretaria Agricultura / A alface é uma das hortaliças de maior importância no Brasil e o estado de São Paulo destaca-se como sendo o maior produtor, gerando uma renda anual de cerca de 40 milhões de reais. Como a virose causada pelo Lettuce mosaic vírus (LMV) é uma das principais doenças da cultura, o presente estudo teve como objetivo avaliar a diversidade, a dinâmica populacional e o papel dos afídeos na disseminação do LMV, em três áreas recentemente destinadas à produção intensiva de alface. Assim, os campos de produção situados nos municípios de Igaratá, Jacareí e Jarinu, foram monitorados durante 12 meses. Foram utilizadas três tipos de armadilhas: adesivas amarelas, para determinar a densidade populacional dos afídeos; de Moericke que proporcionaram a determinação das espécies que apresentavam hábito migratório; e as de azulejo verde Irwin que, sendo mais seletivas, determinaram a atividade de vôo das espécies envolvidas na disseminação do LMV. Constatou-se nas 3 regiões, a predominância de dez espécies de afideos. Dentre as de hábito polífago, destacaram-se as espécies Aphis gossypii, A. fabae, Aulacorthum solani, Macrosiphum euphorbiae e Myzus persicae; já as de hábito oligófago, foram capturadas Hyperomyzus lactucae, Nasonovia ribisnigri, Pemphigius bursarius e Uroleucom ambrosiae. Acyrthosiphon lactucae foi a única espécie monófaga. As amostras de alface foram também coletadas e submetidas a testes sorológicos. Constatou-se, que a incidência do LMV na cultura - 2 - da alface estava relacionada não somente aos picos de vôo das espécies de afídeos, mas também às variedades tolerantes e suscetíveis de alface introduzidas no campo. Observou-se também que a temperatura atuou diretamente na densidade populacional dos afídeos e, conseqüentemente, interferiu na incidência do LMV no campo. A atividade de vôo dos afídeos foi menor durante... . / Lettuce is one of the most important vegetables in Brazil, and the State of São Paulo is the major producer, with an annual revenue of about R$ 40 millions. Since viruses can be limiting factors to this production, the present study was designed to evaluate the diversity and dynamic population of aphids, as well as the role of this vector in the spread of LMV. For this, three regions where intensive production of lettuce was recently introduced in Igaratá, Jacareí and Jarinu were monitored for 12 months. The aphids were caught using yellow adhesive traps for determining the aphid population diversity; Moerick traps were used to evaluate the aphid species with migratory habits; while green tile traps (Irvin), which are more selective, were used to estimate flight activity of species involved in spread of LMV. The predominance of 10 aphid species was observed in the 3 evaluated areas. Among them, Aphis gossypii, A. fabae, Aulacorthum solani, Macrisiphum euphorbiae and Myzus persicae stood out as species with polyphagous habits. Hyperomyzus lactucae, Nasonovia ribisnigri, Pemphigius bursarius and Uroleucom ambrosiae, with olyphagous habits, were also collected. With monophagous habits only Acyrthosiphon lactucae was caught. The lettuce samples were also collected and submitted to serological tests. It was observed that the incidence of LMV in lettuce crops was related not only to the peaks of the aphid flight activity but also to the tolerant and susceptible lettuce varieties introduced to the crop. The temperature acted on the population diversity of the aphids and, consequently, influenced the incidence of LMV. The flight activity of aphids was smaller during the winter, and LMV detection followed this trend even when susceptible varieties were introduced. However, during the other seasons these results were not observed, and the tolerance of the cultivar Elisa... (Complete abstract, click electronic address below).

Orientador: Marcelo Agenor Pavan / Banca: Carlos Frederico Wilcken / Banca: Addolorata Colariccio / Banca: Valdir Atsushi Yuri / Banca: José Alfredo Caran de S. Dias / Resumo: A alface é uma das hortaliças de maior importância no Brasil e o estado de São Paulo destaca-se como sendo o maior produtor, gerando uma renda anual de cerca de 40 milhões de reais. Como a virose causada pelo Lettuce mosaic vírus (LMV) é uma das principais doenças da cultura, o presente estudo teve como objetivo avaliar a diversidade, a dinâmica populacional e o papel dos afídeos na disseminação do LMV, em três áreas recentemente destinadas à produção intensiva de alface. Assim, os campos de produção situados nos municípios de Igaratá, Jacareí e Jarinu, foram monitorados durante 12 meses. Foram utilizadas três tipos de armadilhas: adesivas amarelas, para determinar a densidade populacional dos afídeos; de "Moericke" que proporcionaram a determinação das espécies que apresentavam hábito migratório; e as de azulejo verde "Irwin" que, sendo mais seletivas, determinaram a atividade de vôo das espécies envolvidas na disseminação do LMV. Constatou-se nas 3 regiões, a predominância de dez espécies de afideos. Dentre as de hábito polífago, destacaram-se as espécies Aphis gossypii, A. fabae, Aulacorthum solani, Macrosiphum euphorbiae e Myzus persicae; já as de hábito oligófago, foram capturadas Hyperomyzus lactucae, Nasonovia ribisnigri, Pemphigius bursarius e Uroleucom ambrosiae. Acyrthosiphon lactucae foi a única espécie monófaga. As amostras de alface foram também coletadas e submetidas a testes sorológicos. Constatou-se, que a incidência do LMV na cultura - 2 - da alface estava relacionada não somente aos picos de vôo das espécies de afídeos, mas também às variedades tolerantes e suscetíveis de alface introduzidas no campo. Observou-se também que a temperatura atuou diretamente na densidade populacional dos afídeos e, conseqüentemente, interferiu na incidência do LMV no campo. A atividade de vôo dos afídeos foi menor durante... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: Lettuce is one of the most important vegetables in Brazil, and the State of São Paulo is the major producer, with an annual revenue of about R$ 40 millions. Since viruses can be limiting factors to this production, the present study was designed to evaluate the diversity and dynamic population of aphids, as well as the role of this vector in the spread of LMV. For this, three regions where intensive production of lettuce was recently introduced in Igaratá, Jacareí and Jarinu were monitored for 12 months. The aphids were caught using yellow adhesive traps for determining the aphid population diversity; Moerick traps were used to evaluate the aphid species with migratory habits; while green tile traps (Irvin), which are more selective, were used to estimate flight activity of species involved in spread of LMV. The predominance of 10 aphid species was observed in the 3 evaluated areas. Among them, Aphis gossypii, A. fabae, Aulacorthum solani, Macrisiphum euphorbiae and Myzus persicae stood out as species with polyphagous habits. Hyperomyzus lactucae, Nasonovia ribisnigri, Pemphigius bursarius and Uroleucom ambrosiae, with olyphagous habits, were also collected. With monophagous habits only Acyrthosiphon lactucae was caught. The lettuce samples were also collected and submitted to serological tests. It was observed that the incidence of LMV in lettuce crops was related not only to the peaks of the aphid flight activity but also to the tolerant and susceptible lettuce varieties introduced to the crop. The temperature acted on the population diversity of the aphids and, consequently, influenced the incidence of LMV. The flight activity of aphids was smaller during the winter, and LMV detection followed this trend even when susceptible varieties were introduced. However, during the other seasons these results were not observed, and the tolerance of the cultivar Elisa... (Complete abstract, click electronic address below). / Doutor