Indian Phytopath. 53 (I) : 19-21 (2000) Pathogenic variability of Xanthomonas oryzae pv. oryzae

ABSTRACT: Comparison of virulence of isolates of Xanthomonas oryzae pv. oryzae prevalent in eastern Madhya Pradesh and Punjab on a set of isogenic lines under green house conditions revealed that the isolates prevalent in eastern Madhya Pradesh were more virulent than those prevalent in Punjab. Comparison of reaction of eastern Madhya Pradesh isolates of Xanthomonas oryzae pv. oryzae on a set of differentials with that of their already known reactions against isolates prevalent in Philippines and Japan revealed differences in pathogenicity behaviour of these isolates. Key words: Xanthomonas oryzae pv. oryzae, isolates, virulence, pathogenicity Bacterial leaf blight (Xanthomonas oryzae pv. oryzae) is one of the most wide spread diseases of rice in several rice growing countries. Several resistant cultivars against this disease have been identified and are extensively grown in different parts of the world. However, evolution of new pathotypes have rendered many of these resistant cultivars susceptible. Several isolates of the pathogen are known to occur in differ-ent rice growing countries. Horino (198 I) reported existence of nine bacterial isolates in Indonesia. Six isolates of Xanthomonas oryzae pv. oryzae (Xoo) are known to occur in Philippines (Mew, 1987). Thrimurty et al. (1993) reported existence of six different isolates of Xanthomonas oryzae pv. oryzae in eastern Madhya Pradesh. In the present study, we compared the virulence of isolates of Xanthomonas oryzae pv. oryzae prevalent in eastern Madhya Pradesh and Punjab on a set of isogenic lines obtkined from International Rice Research Insti-tute, Philippines. Comparison of reaction of isolates of Xanthomonas oryzae pv. oryzae prevalent in eastern Madhya Pradesh with that of their known reactions against isolates prevalent in Philippines and Japan was also carried on a set of differentials. *Author for correspondenc