Molecular Variability in Colletotrichum lindemuthianum and Management of bean anthracnose

Abstract

This study was aimed to determine pathogenic and molecular variability in Colletotrichum lindemuthianum, the casual organism of bean anthracnose, to evaluate bean germplasm to find out the sources of resistance against prevalent races; and to identify suitable biocontrol agent and biopesticide for the management of disease. The disease was encountered in almost all the major bean growing areas surveyed and the incidence varied between 0.50 to 88.00 per cent at different stages of crop growth. Virulence spectrum of 90 isolates determined by inoculating each isolate on a set of 12 bean differential cultivars revealed the existence of 29 races in Himachal Pradesh. Race 513 contained maximum number of 16 isolates from diverse geographic regions. Sixteen races namely 101, 103, 115, 119, 195, 537, 551, 581, 598, 613, 615, 631, 639, 707, 775 and 935 were identified for the first time as none of them resembled with previously known races from world over. Out of the 29 races, 24 were virulent on both Andean and Mesoamerican gene pool of Phaseolus vulgaris. Race 0 did not infect any of the differential cultivar. Race 2 infected only Andean gene pool whereas races 1, 513 and 515 infected Mesoamerican gene pool. Interaction studies between virulence and the two gene pools of P. vulgaris suggested four types of interactions (Type I to Type IV). Ten virulence factors were present among 90 isolates on the basis of virulence behaviour with individual differential cultivar. Random amplified polymorphic DNA (RAPD) based fingerprinting with nine most polymorphic primers categorized 90 isolates into two main clusters using 57 per cent as cut off point. There was no congruence between RAPD pattern and virulence phenogram as the isolates that were identical for virulence were often dissimilar for RAPD marker. Evolution model for C. lindemuthianum virulences present in Himachal Pradesh was developed, which categorized 29 races into four evolutionary groups (Group I to Group IV). Races which contain more than six virulence genes may pos