Pathotypes of Colletotrichum graminicola and Seed Transmission of Sorghum Anthracnose

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Abstract
Of 12 isolates, eight pathotypes of Colletotrichum graminicola from four areas (central and southern Texas; Griffin, GA, USA] and Isabela, Puerto Rico) were identified using eight differential grain sorghum [Sorghum bicolor] cultivars in the greenhouse. The Georgia population possessed virulence toward the differential cultivar SC326-6. The same virulence was not detected in the Texas or the Puerto Rico populations. The Texas pathotypes infected the fewest number of differentials. Except for the reaction of SC326-6, isolates from Puerto Rico and Georgia reacted similarly. One Puerto Rico pathotype was tested for possible seed transmission. Seed without visible acervuli showed no seed transmission of C. graminicola under conditions favorable for development of this disease. In seed with acervuli, 23% of the seedlings exhibited necrotic lesions and new acervuli on seedling tissue after 1-2 wk of incubation on sterilized moist vermiculite in enclosed chambers. Anthracnose lesions were observed on mesocotyledonary sheaths, primary leaf laminae, and primary roots.