Genetic architecture and major genes for tuber skin texture in potato

Potato (Solanum tuberosum L.) is a globally important tuber crop and a vital component of the food system. Tuber skin texture is a key quality trait that influences market appearance and is closely associated with resistance to biotic and abiotic stresses as well as tolerance to mechanical damage. However, the genetic basis and regulatory mechanisms underlying this trait remain poorly understood. In this study, we investigated the genetic and molecular mechanisms underlying potato tuber skin texture. A quantitative trait locus (QTL) for tuber skin texture was mapped to a 1.94-Mb interval on chromosome 4 using bulked segregant analysis of a segregating population derived from a cross between russet-skinned variety Innovator and smooth-skinned variety Zhongshuzao43 (Z43). The tuber skin of Innovator contained more cell layers than Z43 and developed progressive cracking during tuber expansion. Innovator also exhibited lower suberin content but higher lignin accumulation in tuber skin compared to Z43. Transcriptome profiling across multiple developmental stages identified a distinct gene expression cluster enriched in pathways related to lignin and suberin biosynthesis. Integrating genes within the QTL with this expression cluster revealed StPXG4, which encodes a peroxygenase, as strongly correlated with skin texture. StPXG4 showed significantly higher expression in commercial smooth-skinned varieties than in russet-skinned varieties. Co-expression analysis further identified two potential upstream regulators of StPXG4, namely StMYB103 and StMYB58. These findings provide key insights into the genetic regulation of tuber skin texture and identify candidate genes that could be targeted to improve tuber appearance and stress tolerance through molecular breeding.