Virulence analysis of Colletotrichum lindemuthianum and its management in common bean

Abstract

newline 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; validation of R genes using molecular markers; and to identify suitable fungicide, biocontrol agents and botanicals for the management of disease. Virulence spectrum of 65 isolates determined on a set of 12 bean differential cultivars revealed the existence of 27 races in North Western Himalayas. Race 503 contained maximum number of 12 isolates from diverse geographic regions. Fifteen races viz; 5, 6, 7, 16, 18, 51, 87, 99, 145, 179, 211, 259, 337, 503 and 1395 were identified for the first time as none of them resembled with previously known races in Himachal Pradesh hence increasing the total number to 44 in the state. The isolates from JandK (3) and Uttrakhand (13) categorized into different races constitute their first record from these two states. The virulence analysis suggested 4 interaction types in accordance with the genetic origin of differential cultivars that were infected by a particular race. Twenty-one races having virulence for genotypes of both the gene pools showed Type IV interaction. Nine of 12 differential cultivars were found to be infected by one isolate suggesting 9 virulence factors among 65 isolates of C. lindemuthianum. RAPD data at 43 per cent similarity coefficient distinguished various isolates into 8 clusters, whereas, ISSR markers categorized test isolates into 5 clusters using 43 per cent similarity coefficient as a cutoff point. There was no congruence between the pathogenic variability and the molecular diversity data, showing no utility of such markers in differentiation of the physiological races whose identity is based on pathogenic behavior of the given isolate involving many pathogenicity factors. Out of 313 accessions, 45 were found resistant to race 0 (20), 17 (21), 503 (19) and 1395 (13), respectively. R-gene prediction analy