Genome editing of susceptibility gene StDND2 enhances Phytophthora resistance in Solanum tuberosum.

Potato (Solanum tuberosum L.) cultivation is severely constrained by multiple pathogens, among which late blight caused by the oomycete P. infestans remains the most destructive disease. Developing pathogen-resistant cultivars can enhance productivity and reduce fungicide use in potato, where R-gene-based resistance is often overcome by evolving pathogen populations. Targeting susceptibility (S) genes represents a promising alternative strategy for improving disease resistance. Here, we employed CRISPR/Cas9 genome editing to introduce a targeted missense single-nucleotide polymorphism in the susceptibility gene StDND2, a putative susceptibility-associated cyclic nucleotide-gated channel family gene showing sequence similarity to Arabidopsis thaliana DND2, to evaluate its association with late blight resistance. The StDND2 sequence was retrieved from the Spud DB database, and guide RNAs targeting the first exon were designed, Cas-OFFinder was used for off-target assessment. Agrobacterium tumefaciens-mediated transformation generated kanamycin-resistant edited lines, which were confirmed by PCR amplification of the Cas9 transgene. Resistance was evaluated using detached leaf assays following inoculation with Phytophthora infestans, and lesion areas were measured at 7 days post-inoculation. Edited lines showed significantly reduced lesion sizes (~74% lower infection rates) compared with empty-vector control plants, without obvious visible developmental abnormalities under the tested growth conditions after visual inspection. These findings provide preliminary evidence that CRISPR/Cas9-mediated editing of StDND2 is associated with reduced late blight severity in potato under controlled experimental conditions and support further evaluation in advanced generations and field environments.