QTL Mapping for Resistance to Bacterial Wilt Caused by Two Isolates of Ralstonia solanacearum in Chili Pepper (Capsicum annuum L.)

Bacterial wilt caused by the β-proteobacterium Ralstonia solanacearum is one of the most destructive soil-borne pathogens in peppers (Capsicum annuum L.) worldwide. Cultivated pepper fields in Korea face a continuous spread of this pathogen due to global warming. The most efficient and sustainable strategy for controlling bacterial wilt is to develop resistant pepper varieties. Resistance, which is quantitatively inherited, occurs differentially depending on R. solanacearum isolates. Therefore, in this study, we aimed to identify resistance quantitative trait loci (QTLs) in two F2 populations derived from self-pollination of a highly resistant pepper cultivar ‘Konesian hot’ using a moderately pathogenic ‘HS’ isolate and a highly pathogenic ‘HWA’ isolate of R. solanacearum for inoculation, via genotyping-by-sequencing analysis. QTL analysis revealed five QTLs, Bwr6w-7.2, Bwr6w-8.1, Bwr6w-9.1, Bwr6w-9.2, and Bwr6w-10.1, conferring resistance to the ‘HS’ isolate with R2 values of 13.05, 12.67, 15.07, 10.46, and 9.69%, respectively, and three QTLs, Bwr6w-5.1, Bwr6w-6.1, and Bwr6w-7.1, resistant to the ‘HWA’ isolate with phenotypic variances of 19.67, 16.50, and 12.56%, respectively. Additionally, six high-resolution melting (HRM) markers closely linked to the QTLs were developed. In all the markers, the mean disease index of the paternal genotype was significantly lower than that of the maternal genotype. The QTLs and HRM markers are expected to be useful for the development of pepper varieties with high resistance to bacterial wilt.