STUDIES ON VIRULENCE REACTIONS OF LOCAL ISOLATES OF XANTHOMONAS ORYZAE PV. ORYZAE

Local isolates of Xanthomonas oryzae pv. oryzae were collected from different rice producing areas of Pakistan and evaluated for their virulence on 12 rice lines viz., IRBB1, IRBB2, IRBB3, IRBB4, IRBB5, IRBB7, IRBB8, IRBB10, IRBB11, IRBB13, IRBB14 and IRBB21. The ability of an isolate to cause lesions with different lengths across the lines was interpreted as virulence. Isolates that were consistently associated with high or low virulence were differentiated. Isolates produced lesions of different sizes on different rice lines. Five virulence groups (races) were identified based on the virulence of the bacterial isolates on these lines. No single gene tested was found to be resistant against all virulence groups prevalent in Pakistan. The results of this study will facilitate the breeders in deployment of effective resistance genes against X. oryzae pv. oryzae strains prevalent in Pakistan.