Evaluation of Cluster Bean Genotypes for Resistance to Charcoal Rot Caused by Macrophomina phaseolina Using Different Host Inoculation Methods

Ten different isolates of Macrophomina phaseolina from cluster bean (Cyamopsis tetragonoloba), selected on the basis of wide geographical distance and potassium chlorate sensitivity, showed remarkable variation in virulence on the susceptible cluster bean genotype, FS 277. Four different host inoculation techniques were employed for resistance screening of six elite cluster bean genotypes under artificial infection conditions using the most pathogenic isolate, MP-6(D). The symptoms induced in the plant tissues from seedling to maturity following artificial inoculation clearly simulated lesions produced under natural conditions. Both greenhouse and field experiments demonstrated significant differences in all parameters-plant weight, plant death, root lesion length and stem lesion length-in all the genotypes tested from seedling stage to pod set. The host inoculation methods described in this study might be useful for screening and analysis of crop varieties' resistance to various other disease infestations. The present investigation involved evaluation of pathogenicity of isolates of M. phaseolina as well as a critical examination of occurrence of resistance to charcoal rot in selected cluster bean genotypes. This is the first report on cluster bean resistance to M. phaseolina. (C) 2005 by The Haworth Press, Inc. All rights reserved.