The development and efficient utilization of molecular markers for the major quantitative trait locus of bacterial wilt resistance in potato

Bacterial wilt, caused by the Ralstonia solanacearum species complex (RSSC), is a severe disease that significantly threatens potato cultivation. Our previous research identified a major strain-specific resistance quantitative trait locus (QTL) on potato chromosome 6, designated as PBWR-6b, which exhibited resistance to Ralstonia pseudosolanacearum (phylotype I/biovar 3) strains of the RSSC, and was most effective at relatively low temperatures. In this study, we compared the nucleotide sequences of one of the candidate genes located within the QTL region of PBWR-6b between the parents used for the QTL analysis. We identified a resistance allele and developed an allele-specific molecular marker (Rbw6-1) for PBWR-6b. This marker assay detected this resistance allele only in genotypes derived from Inca-no-mezame among 107 cultivars and breeding clones; PBWR-6b is thought to have been derived from Solanum tuberosum spp. andigena, which is the hybrid parent of Inca-no-mezame. By utilizing the resistance allele-specific marker, resistant genotypes can be selected from both diploid and tetraploid populations. The inheritance mode of PBWR-6b was then inferred to exhibit dominant inheritance. Furthermore, we developed the Rbw6-2 marker, which can be incorporated into existing multiplex polymerase chain reaction (PCR) methods, to efficiently select resistance genes against bacterial wilt (PBWR-6b), golden cyst nematode (H1), Potato virus Y (Rychc), Potato virus X (Rx1), and late blight (R1 and Saya-akane-derived R2), thus significantly enhancing resistance breeding in potato.