A Threat to Pepper Production: Regional Dominance of Xanthomonas euvesicatoria in Southeastern Türkiye

Bacterial spot disease, caused by Xanthomonas spp., significantly impacts pepper production. This study investigated the prevalence and identity of bacterial spot pathogens in Şanlıurfa and Adıyaman, major pepper-producing regions in Southeastern Türkiye. Field surveys conducted from April to October 2020 collected 171 diseased pepper samples from 76 fields, yielding 122 bacterial isolates (108 from Şanlıurfa, 14 from Adıyaman). Pathogenicity tests on pepper seedlings identified 93 isolates (81 from Şanlıurfa, 12 from Adıyaman) as pathogenic. Xanthomonas euvesicatoria UB-35 isolate obtained from Şanlıurfa showed the highest virulence with a scale value of 4 (on a scale of 0-4). Classical identification tests, including Gram reaction, hypersensitive response, and biochemical assays, combined with molecular analysis using species-specific primers, confirmed that all pathogenic isolates were Xanthomonas euvesicatoria. No other Xanthomonas species were detected. These findings highlight the dominance of X. euvesicatoria in the region.