k-mer analysis of publicly available resources enables rapid development of an improved KASP marker linked to the H1 resistance locus in potato

High-throughput markers for resistance loci are widely used in potato breeding but often benefit from periodic redevelopment to improve diagnostic performance. Here we re-analysed bulked resequencing data generated by Meade et al. (2020) to redesign a KASP marker for the H1 potato cyst nematode resistance locus. We applied the CoSSA k -mer subtraction approach to sequencing pools generated by Meade et al., extracting H1 -associated k -mers and mapping them to the DM reference genome to identify candidate SNPs near the diagnostic 57R region. Two SNPs were converted to KASP assays, of which one produced a modest but statistically significant improvement in classification accuracy relative to the previously published marker when tested across three years of breeding material. This study therefore provides a practical, low-cost workflow to modernise legacy markers by converting reference-free k -mer signals into breeder-ready assays for potato improvement.