Pathogenic and Molecular Variability Among Twelve Isolates of Colletotrichum graminicola from Sorghum

Variability in 12 foliar and grain isolates of sorghum anthracnose pathogen Colletotrichum graminicola was studied through virulence and Random Amplified Polymorphic DNA ( RAPD) assay. For virulence analysis, pot grown 21-day-old plants of six differential sorghum lines were spray inoculated with conidia (1 x 105 conidia ml-1). The isolates showed significant (P< 0.05) variations in latent period, aggressiveness and virulence. Overall pathogenic potential was determined as Virulence Index. Hierarchical clustering using euclidean test based on "Virulence Index" grouped the 12 isolates into three groups, while that based on RAPDs using primer OPA8 grouped these into four groups. Monoconidial isolate Cg 226-3 had 85% genetic and pathogenic similarity like its parent, while Cg 227-3 showed virulence variation and 65% genetic similarity with its parent, indicating heterogeneity in Cg 227