Characterization of pathogenic variability of Xanthomonas oryzae pv oryzae isolates causing bacterial leaf blight disease in Malaysian rice granaries

Abstract

Xanthomonas oryzae pv oryzae, the causative pathogen of bacterial leaf blight (BB) disease is one of the most prevalent rice diseases in Malaysia. Breeding for resistance requires information on the pathogenic variability of X. oryzae for decision-making on the deployment of appropriate resistance genes. In this study, nine Near Isogenic rice Lines (NILs) carrying single BB resistance genes (Xa) used to characterize the virulence of 40 X. oryzae isolates collected from Malaysian rice granaries. The results revealed a highly diverse pathogenic profile, consisting of 21 distinct X. oryzae races named R1 to R21. Race R20, followed by R16 were identified as dominant, showing the highest frequency. Although no Xa genes have been used in Malaysian rice granaries up to now, unexpectedly race R20 was found virulent to most of the NILs carrying the Xa genes. However, the wide distribution of avirulence gene avrxa5 and avrXa7 among the isolates indicated that the population was most effective to NILs carrying the xa5 and Xa7 genes. The information obtained helps to understand the virulence of X. oryzae population and facilitates an adequate gene deployment to increase BB disease resistance in Malaysia.