Genome-Wide Identification of β-D-Xylosidase Gene Family in Potato and Functional Analysis Under Alkaline Stress

β-D-xylosidase (BXL) is a key enzyme involved in xylan degradation and plays crucial roles in plant development and stress responses. However, its functional roles in potato (<i>Solanum tuberosum</i>) remain poorly understood. In this study, we performed a genome-wide identification of the <i>StBXL</i> gene family and identified eight <i>StBXL</i> genes distributed across five chromosomes. A phylogenetic analysis classified these genes into four groups. Conserved motif and domain analyses indicated functional conservation among StBXL proteins. Analyses of cis-acting elements in the promoters and expression profiles of <i>StBXL</i> genes in various plant tissues under different stress treatments revealed their spatiotemporal expression patterns, as well as potential roles in phytohormone signaling and stress responses. Alkali stress significantly inhibited the expression of <i>StBXL4</i> and <i>StBXL5.</i> The overexpression of <i>StBXL4</i> enhanced the sensitivity of potato seedlings to alkali stress, whereas the overexpression of <i>StBXL5</i> showed no significant phenotypic differences under the same conditions. These results suggest that <i>StBXL4</i> acts as a negative regulator of the alkali stress response in potato. This study fills the research gap regarding the potato <i>StBXL</i> gene family and provides valuable insights for the molecular breeding of alkali-tolerant potato varieties.