Evaluation of Common Bean Cultivars for their Resistance Against Xanthomonas Axonopodis Pv. Phaseoli

Abstract

Common bacterial blight (CBB) caused by the bacterium Xanthomonas axonopodis pv.phaseoli (Xap), is an economically important disease of beans worldwide. Since there wasno satisfactory chemical control for the disease, use of resistant cultivars is an important management strategy. The main objective of this study was to determine CBB reaction oftwenty different bean genotypes breed and/or maintained by Melkassa Agricultural Research Center. The genotypes were evaluated under field and greenhouse conditions for their reaction to Xap following leaf-spray inoculation with bacterial suspension of 10 8cfu/ml. Disease was ratted with 0 - 9 visual scale and the percent severity index (PSI)was calculated. The results revealed that the evaluated genotypes showed various levelof reaction to Xap. Three genotypes GLP-2, ECAB005 and Gobe Rasha were showed resistant reaction against Xap. Eleven genotypes showed moderately susceptible disease reaction with mean disease severity rating values ranging from 3.57- 5.00 while sixgenotypes were categorized as susceptible and one genotype Mexcan-142 showed highsusceptibility. The study results were in a conclusion that there is a resistant gene in theresistant and moderately susceptible genotypes. Therefore, the resistant genotypesshould be promoted in bean production system to increase common bean production and productivity in reducing CBB epidemics and associated yield loss. Moreover, theresistant and moderately susceptible genotypes identified can be used as possible sources of resistance for breeding program against CBB to improve the susceptibility ofcommercial bean cultivars commonly cultivated in the study area.