Variations in random amplified polymorphic DNA profile and toxin production among isolates of Colletotrichum falcatum Went from sugarcane in Tamil Nadu,India

Red rot, caused by Colletotrichum falcatum Went, is one of the most important diseases of sugarcane (Saccharum officinarum L.). The pathogen shows a great diversity in virulence as a number of pathotypes are known to occur in nature. In the present study, the toxin producing ability and genetic variability among isolates of C. falcatum collected from major sugarcane growing areas of Tamil Nadu, India were analysed. The C. falcatum isolates differed significantly in their ability to produce toxin in vitro. The toxin from C. falcatum isolate Cf 671a induced the maximum electrolyte leakage (300 μS) from sugarcane leaf tissues. The genetic relatedness of the isolates of C. falcatum differing in toxin production potential was investigated by using RAPD analysis. Analysis of the genetic coefficient matrix derived from the scores of RAPD profiles showed that minimum and maximum percent similarities among the tested C. falcatum isolates were in the range of 19 to 95% respectively. The phylogenetic analysis by the UPGMA identified two main clusters. Cluster A contains only one isolate (Cf 98061) and all the other isolates were placed in Cluster B confirming high genetic diversity among the isolates. No correlation was observed between clustering of the C. falcatum isolates in the dendrogram and their toxin producing abilities.