New Insights into the Role of Secondary Metabolic Pathways in Resistance of Potato to .

causes soft rot in potato ( L.) tubers. We used bulk RNA-seq to compare the early transcriptional responses of the diploid F genotypes from the mapping population that varied in tuber resistance to . RNA was collected from wounded tubers inoculated with (B), wounded tubers treated with sterile water (W), and non-treated tubers (NT) at 8, 24, and 48 hours post-inoculation (hpi). The largest transcriptional divergence between resistant (R) and susceptible (S) genotypes occurred at 8 hpi, with R tubers showing stronger induction of phenylpropanoid biosynthesis, phenylalanine and tyrosine metabolism, amino sugar and nucleotide sugar metabolism, isoquinoline alkaloid biosynthesis, and glutathione metabolism. Phenylpropanoid biosynthesis was dominant in R tubers, in 17 differentially expressed genes (DEGs), consistent with rapid suberin and lignin deposition as a physical barrier. RT-qPCR of nine defence-related genes corroborated the RNA-seq trends. The suberisation-associated anionic peroxidase was located within a QTL for resistance on chromosome II, supporting its role as a candidate for future functional studies. This is the first transcriptome-based comparison of R and S potato genotypes challenged with , providing candidate pathways and genes that may guide future molecular breeding once their roles are validated.