Resistance of Pepper Cultivars to Ralstonia solanacearum Isolates from Major Cultivated Areas of Chili Peppers in Korea

Bacterial wilt, caused by Ralstonia solanacearum, is a serious disease in chili pepper (Capsicum annuum L.) and is gradually increasing due to climate change in Korea. In this study, we collected 14 R. solanacearum isolates from 12 major cultivated areas of chili pepper and analyzed their biovar and pathogenicity. The biovar test categorized the 14 isolates into two groups, biovar 3 and biovar 4. Their pathogenicity was further analyzed using 12 commercial pepper cultivars including two controls, 'Geonchowang' (susceptible) and 'Konesian Hot' (resistant). The isolates were divided into six groups based on their pathogenicity and the pepper cultivars were divided into four groups according to their resistance to the 14 isolates. Isolates of group I had the strongest pathogenicity and isolates of group VI had the weakest pathogenicity to the 12 pepper cultivars. Pepper groups B, C, and D were moderately resistant or resistant to some isolates, but the resistance in these cultivars was not as strong as the resistant control 'Konesian Hot'. These results suggest that R. solanacearum isolates from Korea can be classified by their pathogenicity using five different pepper cultivars. This study provides useful information on the biovar distribution ofR. solanacearum in Korea and on the selection of genetic resources available for bacterial wilt resistance breeding.