Abstract:

Bacteria are major pathogens leading to destructive disease inflicting considerable quantitative and qualitative losses in pomegranate. Characterisation of isolates and identification of new strains enables assessment of the evolution of virulence and symptomology. It also helps design better control and management practices. The present study aimed to isolate and characterise biochemical and molecular methods of bacteria from 4 taluks of Chitradurga district, Karnataka, India, with a unique agro-climatic zone. The results of the study report through staining, cultural, and biochemical studies a total of 17 bacterial isolates belonging to Pseudomonas spp., and Erwinia spp. and Xanthomonas species. Isolates of X. axonopodis pv. punicae (Xap) were isolated using selective-medium. Further, staining, cultural, biochemical and molecular variability identified 4 isolates of X. axonopodis pv. punicae (Xap) (Xa-1, Xa-2, Xc-3, Xc-4). The 16sRNA gene analysis indicated the Xc-4 strain was unique, as evidenced by the phylogenetic tree. A strong correlation between in vitro studies and disease severity in the indicator plant assay was observed. In summary, a consortia of bacteria predominantly belonging to Xanthomonas was identified in the Chitradurga area of Pomogranate plants. Evolution of the pathogen in this district could be proposed to be driven by genetic substrates enabling molecular evolution due to its host specificity and other environmental factors. The study has implications for pathogenicity, disease severity and virulence studies. Further, it bears implications in agriculture and the fruit industry with implications for fruit quality and post-harvest technology.