José Luiz Lopes Gomes

Adaptabilidade e estabilidade de genótipos de soja avaliados para resistência ao oídio

The objective of this research was to identify soybean genotypes with good adaptability and stability of behavior for resistance to powdery mildew in field conditions. The work was carried out at the Professor Diogo Alves de Mello Experimental Station, Agronomy Department of the Federal University of Vicosa (UFV), Vicosa, Minas Gerais. The experiment was arranged in a randomized block design, in split-plots, with 15 genotypes (plots) and seven evaluation times (subplots), with four repetitions. Evaluation of incidence and severity of powdery mildew in the genotypes were accomplished by visual quantification of fungus infection level (IL), assessing the level of infection of the leaf area infected (NIAFI) by the powdery mildew and the level of infection of the most infected leaflet (NIFI). Data were examined by analysis of variance and analysis of adaptability and stability according to EBERHART & RUSSELL (1966). The results allowed to get to the following conclusions: the genotypes that showed the highest resistance levels, were, in general, also the ones of higher adaptability and stability, both for NIAFI and NIFI, standing out UFV 89-361826 T2, UFV 94-334268, UFV-16 and UFV-19, FT-10 RC5 (F3), FT-Abyara RC6 (F2), Doko RC, FT-Abyara RC5 (F4), whereas the most susceptible genotypes were the ones of worse predictability, standing out UFV 94-5126, FT-104, UFV 94-3500, FT-Cristalina, FT-Estrela and BR-16.

Resistance to stem canker, frogeye leaf spot and powdery mildew of soybean lines lacking lipoxigenases in the seeds

A cultura da soja [Glycine max (L.) Merrill] ocupa lugar de destaque na economia brasileira, tanto em termos de area plantada, quanto de producao de graos. A presenca de gosto de feijao cru tem sido limitante para o consumo de derivados de soja pelos povos ocidentais. Esse sabor caracteristico e proporcionado pelas enzimas lipoxigenases (Lox1, Lox2 e Lox3). A eliminacao dessas enzimas, pela manipulacao genetica dos alelos que as codificam, e a maneira mais adequada de contornar os problemas associados ao sabor desagradavel. Visando elucidar a participacao das lipoxigenases, no processo de resistencia da soja a patogenos, variedades normais de soja (FT-Cristalina RCH, Doko RC e IAC-12) e suas respectivas linhagens obtidas por retrocruzamentos, sem as tres lipoxigenases nas sementes (triplo-nulas - TN) e com as tres lipoxigenases (triplo-positivas - TP), foram testadas quanto as suas resistencias ao cancro-da-haste (Diaporthe phaseolorum f.sp. meridionalis), a cercosporiose (Cercospora sojina Hara) e ao oidio (Microsphaera diffusa Cke. & Pk.). Todos os materiais geneticos foram resistentes ao cancro-da-haste. Com relacao a cercosporiose, FT-Cristalina RCH e Doko-RC e suas respectivas linhagens com ou sem lipoxigenases mostraram-se resistentes, enquanto IAC-12 e suas linhagens derivadas mostraram indices de doenca mais elevados, sendo que as linhagens IAC-12 TP e TN foram mais suscetiveis, indicando perda de gene de resistencia nos retrocruzamentos. Nao houve relacao entre retirada dos genes que codificam lipoxigenases nas sementes com a resistencia a cercosporiose. No caso do oidio, as linhagens TP ou TN apresentaram-se similares ou pouco mais resistentes que seus respectivos progenitores recorrentes, os quais se mostraram suscetiveis na seguinte ordem: IAC-12, menos suscetivel, Doko-RC, intermediario e FT-Cristalina RCH, mais suscetivel.