Characterization of Acidovorax avenae subsp. avenae causing bacterial leaf streak of maize in Punjab state of India

Twenty five isolates of Acidovorax avenae subsp. avenae causing bacterial leaf streak collected from infected maize crop grown in different geographical regions of Punjab, northern India were characterized for their molecular diversity using twenty five random amplified polymorphic DNA (RAPD) markers. All the primers showed amplification with a total of 1769 amplified fragments. Among RAPD primers, S112 was found to be highly polymorphic with PIC value of 0.95 while OPT-4 was least polymorphic. The size of amplified DNA fragments ranged from 59bp to 3.9kbp. Dendrogram based on molecular data generated by 25 RAPD collectively divided all 25 isolates into four groups. From 25 isolates, 20 were used for their pathological characterization and based on the multivar cluster analysis of pathogenicity data, these were divided into three groups, each producing a distinct range of disease score on particular maize inbred/hybrid used in this study. Isolate Aaa2 was found to be the most virulent with an average disease score of 8.6, whereas Aaa17 was found least virulent with average disease score of 5.1. The most virulent isolates of this pathogen were present in central Punjab. This was the first attempt to study the genetic diversity and pathogenic variation in Punjab populations of A. avenae subsp. avenae.