Development of KASP marker to enhance breeding efficiency for phytophthora blight resistance in sesame through QTL...

Phytophthora blight, caused by Phytophthora nicotianae, is a destructive disease that severely affects sesame (Sesamum indicum L.). Developing resistant cultivars remains the most effective management strategy. This study aimed to identify genomic regions associated with Phytophthora blight resistance and to develop molecular markers for use in sesame breeding.

Whole-genome resequencing (WGS) was performed for the resistant cultivar Geonbaek, the susceptible cultivar Milsung, and 99 recombinant inbred lines (RILs). Using a high-density genetic map, we identified a major resistance locus on chromosome 10, designated qPB10. The IM-ADD analysis defined a 0.51-Mb marker interval with an LOD score of 25.67, and a complementary binary-trait analysis independently detected the same locus at 75.10 cM. Genomic analysis of the target region revealed several immune-related genes, including clusters encoding nucleotide-binding leucine-rich repeat (NLR) proteins and other defense-associated factors. To utilize these findings in breeding, kompetitive allele-specific PCR (KASP) markers were developed based on sequence polymorphisms within the qPB10 interval. Validation using the RIL population and a diverse panel of sesame cultivars identified a robust marker that reliably discriminates resistant genotypes.

These findings establish qPB10 as the primary locus governing Phytophthora blight resistance in sesame. The KASP markers developed in this study enable efficient marker-assisted selection without the need for extensive disease phenotyping. These results provide a practical genomic resource for accelerated breeding of resistant cultivars and establish a foundation for future functional characterization of resistance mechanisms.