Isolation and characterization of Xanthomonas oryzae pv. oryzae isolates from North West Frontier Province (NWFP) Pakistan

Xanthomonas oryzae pv. oryzae the causal agent of bacterial leaf blight (BLB) of rice was characterized through pathogenecity and biochemical assays. Plant samples were collected from major agro-ecological rice zones including Lower Dir, Swat and Agricultural Research Station, Mingora in NWFP during 2002. The isolates obtained were subjected to pathogenecity test on six rice cultivars that varied significantly in terms of disease severity among each other. However, non-significant results were recorded when clip and pinprick methods of leaf inoculation were compared for pathogenecity test. The isolates were also subjected to different biochemical tests and were found to be negative for Oxidase, Lecithinase and Gram reactions. Results of biochemical tests like Tween 80 and Starch Hydrolysis, Anaerobic nature and Acid Production from Carbohydrates varied among the isolates. Only 20% isolates were similar in terms of their reactions to these tests. Based on biochemical responses it was established that despite the small sample size (n=15) genetic variability was detected in Xanthomonas oryzae pv. oryzue isolates.