AVALIAÇÃO DA SEVERIDADE DO OÍDIO [Erisyphe diffusa (U. Braun & S. Takam)] EM GENÓTIPOS DE SOJA, EM CONDIÇÕES DE CAMPO

Abstract

The development of soybean cultivars adapted to different regions and generation technologies contribute to Brazil to increase its production, placing it as the second largest world producer and exporter of grain. Several factors have limited its production among these diseases, approximately 40 already identified in Brazil, especially powdery mildew (Erysiphe diffusa U. Braun & S. Takami), one of the most important, resulting in reductions of up to 40% in income susceptible cultivars. The study aimed to evaluate the severity of powdery mildew on soybean genotypes during seven seasons of evaluation, by analyzing disease progress, using regression. It was developed at the Federal University of Viçosa, Minas Gerais arranged in split plots inrandomized block design seven evaluations were performed by visual quantification of the level of infection of leaf area infected (NIAFI). Regression analysis was performed to check the progress of thedisease. The results showed that the method is efficient for such studies, showing clearly the evolution of the disease, and aiding in the discrimination of resistant and susceptible genotypes at the third assessment. Stood out as sources of resistance genotypes UFV-16, UFV-19, UFV 89-361826T2, FT-Abyara RC5 (F4), FT-RC6 Abyara (F2), FT-10 RC5 (F3), Doko RC, UFV UFV 95-4121333 and UFV 94-334268. FT-104 and FT-Crystalina stood out as susceptible and BR-16 and FT-Estrela as highly susceptible, while the other showed intermediate behavior.