VIRULENCE SPECTRUM OF SOUTH-AMERICAN ISOLATES OF COLLETOTRICHUM-GLOEOSPORIOIDES ON SELECTED STYLOSANTHES-GUIANENSIS GENOTYPES

Anthracnose, caused by Colletotrichum gloeosporioides, is the most imp ortant and widespread disease of Stylosanthes, a diverse tropical and subtropical forage legume naturally distributed in Central and South A merica. Although South American isolates of C. gloeosporioides are kno wn to be variable in pathogenicity, no suitable differential host line s have been identified to fully characterize them. This study takes ad vantage of new S. guianensis inbred lines, cultivars, and accessions t o describe the pathogenicity of South American isolates of C. gloeospo rioides and to select potentially useful differentials. Seedlings of 2 3 S. guianensis genotypes were inoculated with 45 isolates from variou s regions of South America. Virulence patterns were used to select 12 differentials and determine 23 pathotypes in C. gloeosporioides. In co ntrast, the same isolates were grouped into nine pathotypes with the f our Australian differentials currently in use.