A KASP Marker for the Potato Late Blight Resistance Gene RB/Rpi-blb1

The disease late blight is a threat to potato production worldwide, making genetic resistance an important target for breeding. The resistance gene RB/Rpi-blb1 is effective against most strains of the causal pathogen, Phytophthora infestans. Until now, potato breeders have utilized a Sequence Characterized Amplified Region (SCAR) marker to screen for RB. Our objective was to design and validate a Kompetitive Allele Specific PCR (KASP) marker, which has advantages for high-throughput screening. First, the accuracy of the SCAR marker was confirmed in two segregating tetraploid populations. Then, using whole genome sequencing data for two RB-positive segregants and a diverse set of 23 RB-negative varieties, a SNP in the 5' untranslated (UTR) region was identified as unique to RB. The KASP marker based on this SNP, which had 100% accuracy in the cultivated diversity panel, was used to generate diploid breeding lines containing RB. The KASP marker is publicly available for others to utilize.