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

<i>Dickeya solani</i> causes soft rot in potato (<i>Solanum tuberosum</i> L.) tubers. We used bulk RNA-seq to compare the early transcriptional responses of the diploid F₁ genotypes from the mapping population that varied in tuber resistance to <i>D. solani</i>. RNA was collected from wounded tubers inoculated with <i>D. solani</i> (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 <i>POPA</i> was located within a QTL for <i>D. solani</i> 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 <i>D. solani</i>, providing candidate pathways and genes that may guide future molecular breeding once their roles are validated.