RAPD and virulence analyses of Colletotrichum capski isolates from chilli (Capsicum annuum)

Abstract

Chilli (Capsicum annuum) fruits showing symptoms of an-thracnose disease were collected from farmer’s fields in different chilli-growing areas of Tamil Nadu, India, and fungal pathogens were isolated from the infected fruits. The isolates were identified as Colletotrichum capsici, C. gloeosporioides and Alternaria alternata, based on morphological and cultural characters. Colletotrichum capsici was the most commonly isolated fungal species from infected chilli fruits. The virulence of all the fungal isolates was determined in vitro by artificial inoculation on detached chilli fruits (cv. K2). The measurement of disease severity of chilli revealed differences in the virulence between isolates. The molecular variability among isolates of C. capsici that differed in virulence was analysed by means of random amplified polymorphic DNA (RAPD), using 22 random primers. Analysis of the genetic coefficient matrix derived from the scores of RAPD profile showed that minimum and maximum per cent similarities among the C. capsici were in the range of 16 to 81% respectively. Cluster analysis, using the unweighted pair-group method with arithmetic average (UPGMA), clearly separated the isolates into three clusters (I, II and III), confirming the genetic diversity among the isolates of C. capsici from chilli. Cluster III consisted of only one isolate (CBE1), cluster II consisted of two isolates (TEN 3 and TEN 4) and all the remaining isolates belonged to cluster I. No relationship between clustering in the dendrograms and virulence of C. capsici isolates was observed.