OCCURRENCE OF COMMON BACTERIAL BLIGHT CAUSED BY Xanthomonas axonopodis pv. phaseoli ON COMMON BEAN AND THE INFLUENCE OF DIFFERENT FACTORS ON IT’S INCIDENCE IN UASIN GISHU COUNTY

Abstract

Beans (Phaseolus vulgaris) is a popular legume crop in Kenya, ranking first among the legumes in importance. The production of this crop in Kenya has not kept pace with the demand. Among the main causes for poor yields in common beans are bacterial diseases of which common bacterial blight caused by Xanthomonas axonopodis pv. phaseoli (Xap), is a major seed-borne disease of common bean worldwide and can cause 10 to 40% loss in yield. A survey was carried out in 60 farms in three sub counties of UasinGishucounty, to establish occurrence of common bacterial blight, during the rainy seasons between April - June and September – December, which are the main bean production seasons. The disease incidence was determined in each farm by taking four quadrants at random, in each quadrant the number of plants showing disease symptoms were counted against the total number of plants in the quadrant and the means were used as the disease incidence of each farm. The altitude which determines the agro ecological zone was established from the reading of Geographical Positioning System equipment (GPS). Diseased plant parts were collected and the bacteria isolated. The isolates obtained were confirmed through gram staining, microscopy, biochemical and pathogenicity tests. Farmer practices were determined through questionnaires and farmers’ interview. Descriptive statistics, Chi-square tests and spearman’s correlation coefficient analysis were used for data analysis and correlations. Common bacterial blight disease incidence in the individual farms varied from 13.2 to 32.5%. There was a significant correlation between altitude and common bacterial blight incidence. The Pearson’s correlation coefficient (p<0.01) indicated a reduction in common bacterial blight incidence as altitude increased. The disease also reduced with an increase in the number of seasons the field was occupied by other crops besides beans. There was a wide spread occurrence of the disease, and major contributing factors to common bacterial blight in the region include; seed source, bean variety, lack of seed renewal and the method of production. The survey provides back ground information useful in the disease management in the region in order to improve bean production consequently increasing the yields.