The diversity and overwintering of Colletotrichum coccodes in tomato fields in southwestern Ontario

At least fifteen distinct biotypes of Colletotrichum coccodes were characterized from 435 isolates obtained from diseased tomato (Lycopersicon esculentum) fruit and leaves of various commercial processing tomato cultivars and breeding lines. These biotypes differed in pathogenicity, spore production, spore size, growth rate and cultural characteristics in potato dextrose agar. The differences in pathogenicity were demonstrated by inoculations made on mature green fruit of several tomato cultivars. Spores of C. coccodes were able to overwinter in infected plant debris in the field. Since the fungus can overwinter in southwestern Ontario and also parasitize a local common weed (velvetleaf) and potato, it is evident that these biotypes should be stable in this region if introduction from outside is prevented.