PHENOTYPIC DIVERSITY OF XANTHOMONAS-ORYZAE PV ORYZAE IN NEPAL

Fifty-three strains of Xanthomonas oryzae pv. oryzae collected from various rice-growing areas in Nepal were characterized for differences in biochemical and physiological characteristics, bacteriocin production, and virulence. Numerical analysis of phenotypic features revealed that all strains were associated at 82.4% similarity of coefficient (S(sm)) in the dendrogram. No distinct phenons were observed, suggesting homogeneous populations of X. o. oryzae. Forty-four percent of the strains produced bacteriocin, and six bacteriocin groups were distinguished. Inoculation of X. o. oryzae strains on five IRRI differential rice cultivars (IR8, IR20, IR1545-339-2-2, Cas209, and DV85) and three Nepalese rice cultivars (Himali, Laxmi, and Sabitri) demonstrated significant cultivar-strain interaction. As a result, nine pathogenic races of X. o. oryzae were detected. Race 1 isolated from Nepal was similar to race 6 of the Philippines X. o. oryzae. No relationship was observed between virulence and physiological characteristics or bacteriocin production.