Journal of Plant Pathology & Microbiology

Abstract

Occurrence and Importance of Xanthomonas axonopodis pv. Phaseoli in Common Bean (Phaseolus vulgaris L) Seed Produced under Different Seed Production System in Central Rift Valley of Ethiopia

Leta A, Lamessa F and Ayana G

Common bacterial blight of bean caused by the seed-borne bacteria Xanthomonas axonopodis pv. phaseoli (Xap) (Smith) Vauterin and X. axonopodis pv. phaseoli var. fuscans (Burkholder) Starr and Burkholder is one of the most constraint of common bean production all over the world. The pathogen is seed-borne and survives as long as the seed remains viable. Use of pathogen-free seeds has been the main method used to control the disease in most bean production areas, and detection of this pathogen in seeds is essential for effective disease control. This study was carried out to detect and characterize Xap in seed lots collected from different seed dealers and local markets in Central Rift Valley of Ethiopia. A semi-selective medium Xanthomonas campestris pv. phaseoli (XCP1) and yeast extract-dextrose-calcium carbonate agar (YDCA) were used to recover the bacterium from whole bean seed extract and direct seed plating respectively. The pathogenicity test was done on Mexcan-142 bean cultivar to confirm pathogen identification. Colonies of the bacterium were yellow, mucoid and convex on XCP1 media and zone of hydrolysis formed around them. Further biochemical test results also confirm that the colonies were gram negative, rod shape and hydrolyze starch, casein and Tween80. The results confirmed the presence of seed borne Xap in all seed dealers and local market seed lots in the study area. The result reveled Xap was prevalent in 79.27% of the total seed samples collected. Lower prevalence (21.43%), seed infection percentage (1.643%) and bacterial population were resulted in seed lots from Melkassa Agricultural Research Center seed lots; while the higher prevalence, seed infection percentage and bacterial population were observed in cooperative union, local market, and seed producer’s cooperative seed lots. From the result, it can be concluded that Xap was potentially recovered from naturally infected seeds using XCP1 media and the pathogen is highly distributed in seed lots in the study area with high prevalence in farmer’s produced seed lots. Therefore, seed plating on semi selective medium XCP1 can be used as standard method for routine analysis of Xap from bean seeds. Seed dealers in the study area should follow strict disease free seed production programs and farmers in the study area should be encouraged not to use local market and/or their own saved seeds for planting purpose.