Sphaerotheca fuliginea is the causal agent of powdery mildew, one of the most important cucurbit diseases in Brazil. Disease control is achieved by using fungicides, but resistant varieties of cultivars can also be used. This fungus presents physiological specificity in melons with race 1 being apparently prevalent in Brazil and world wide. Knowledge of prevalent races of the pathogen in a specific region is of vital importance to plant breeders. In this research a total of 31 isolates was obtained from different cucurbit species, showing symptoms of powdery mildew, cultivated in several Brazilian States. All isolates were identified as S. fuliginea. Isolates were maintained on plants growing in the greenhouse and evaluated for virulence on a set of differential melon and one watermelon cultivars. Twenty-one isolates were identified as race 1, and eight as race 2. Two isolates from watermelon were considered specific to this species because they infected only the cultivar "Crimson Sweet" of watermelon. Race 1 is the most prevalent in Brazil and race 2 is present in the Federal District. Race 2 seems to be adapted to greenhouse conditions as the isolates from this race were found only under this specific condition. This is the first report of race 2 of S. fuliginea in the Federal District of Brazil.
Cucumis melo; Cucumis sativus; Citrullus lanatus; Cucurbita spp.; powdery mildew; plant breeding
