BSA-seq-based identification of candidates associated with stable resistance to Ralstonia pseudosolanacearum in pepper.

Bacterial wilt is a major constraint on pepper production, and the development of resistant cultivars is the most effective and sustainable strategy for disease management. However, pepper germplasm with stable resistance and its genetic basis remain insufficiently characterized. In this study, 63 pepper accessions were screened for bacterial wilt resistance using a leaf-to-whole plant bioassay. Based on disease severity index values, seven accessions were classified as extremely resistant (ER), 25 as resistant, 22 as moderately susceptible, and nine as susceptible. Selected accessions were further evaluated against five Ralstonia pseudosolanacearum strains with distinct pathogenic and genetic characteristics. Most ER accessions maintained strong resistance across diverse pathogen backgrounds, although their resistance levels varied among strains, suggesting the involvement of multiple resistance factors. To identify resistance-associated genomic regions, bulked segregant analysis sequencing (BSA-seq)-based QTL analysis was performed using an F2 population of 398 individuals derived from a cross between an ER accession ('MC4') and a susceptible accession ('Subicho'). Two candidate regions were identified on chromosomes 8 and 11. These regions contained candidate genes encoding LCB1-like, CABIN1, NAR1, and G3BP-like proteins. These findings provide useful genetic resources and candidate loci for further investigation and breeding of bacterial wilt-resistant pepper.