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

ABSTRACT 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.