Characterization of Xanthomonas campestris pv. viticola causing bacterial leaf spot of grapes in Maharashtra, India

ABSTRACT

Aim: The aim of the present study was to isolate, characterize and identify pathogenic bacteria from bacterial leaf spot infected grape vineyards of Maharashtra. Methodology: Collected diseased samples were subjected to isolation. All isolates were further subjected to different morphological and biochemical characterization. These isolates were also used to standardize inoculation methods to study host range and test pathogenicity to confirm infectivity. Genomic DNA was isolated from bacteria for phylogeneitc analysis using 16 rDNA. Results: The disease is characterized by water soaked, angular leaf spot which later turns to irregular, dark brown to black necrotic region on the leaf surface. Microbial studies confirmed that it is a Gram negative, rod shaped bacterium with white, mucoid, glistening and convex circular colonies on artificial medium. Pathogenicity test was performed to confirm virulence. Phylogenetic analysis of 16S rDNA gene exhibited more than 99% similarity with other Xanthomonas campestris pv. viticola. The bacterium was found resistant to vancomycin, peniciliin and oxacillin antibiotics. The bacterium is also capable of infecting Mangifera indica and Citrus limon along with eight weed species.