Characterization of xanthomonas strains causing bacterial leaf spot in capsicum

Abstract:

Bacterial leaf spot (BLS) caused by Xanthomonas spp. destroys 20–60% of capsicum yield annually in western India, yet the pathogen's strain-level diversity in Gujarat remains poorly documented. This research characterised seven Xanthomonas isolates collected from symptomatic capsicum fields across Navsari and Dantiwada districts during the 2022 kharif season. Morphological, biochemical (LOPAT), molecular (16S rDNA sequencing), and pathogenicity tests were performed at Navsari Agricultural University. All seven isolates were confirmed as Xanthomonas euvesicatoria. Disease severity on five capsicum cultivars ranged from 1.1 to 4.9 on a 1–5 scale. Strains XCV-02 and XCV-05 were the most aggressive, producing disease scores above 4.0 on susceptible cultivars California Wonder and Arka Mohini. Antibiotic sensitivity tests showed that streptomycin sulphate at 500 ppm gave the widest inhibition zones. The findings provide a strain-level baseline for designing targeted resistance breeding and chemical management strategies against BLS in Gujarat.