Effects of foliar application of exogenous selenium on anthocyanin biosynthesis in tubers of light purple-fleshed potatoes

This study investigated how foliar selenium (Se) application affects chlorogenic acid, total phenols, flavonoids, and anthocyanins in light purple-fleshed potatoes, as well as the expression of genes involved in the anthocyanin biosynthesis pathway, with the aim of identifying the optimal external Se concentration and spray frequency to promote anthocyanin accumulation in tubers. The purple-skinned, light purple-fleshed cultivar ‘Diancaishu 104’ was used as the experimental material. Sodium selenite was applied by foliar spraying at three Se concentrations: 0 (distilled water, CK), 5 (Se1), and 10 mg L⁻¹ (Se2), with two application frequencies (2 or 3 sprays). For the two-spray treatment, applications were performed at the tuber formation and tuber bulking stages; for the three-spray treatment, applications were performed at the tuber formation, tuber bulking, and tuber maturation stages, giving a total of five treatments. Chlorogenic acid, total phenols, flavonoids, and anthocyanins were quantified, and the expression of anthocyanin pathway-related genes was analyzed. The results showed that two sprays of Se1 more effectively promoted anthocyanin synthesis in potatoes. Specifically, two foliar sprays of Se1 significantly upregulated StF3'5'H, StCHS, StDFR, StANS, and StMYB113 expression in the skin by 9.11-10.11-fold, and increased StCHS and StDFR expression in the flesh by 2.99-3.72-fold. In contrast, three sprays of Se2 were more effective at increasing chlorogenic acid and total phenols in tubers, raising their contents by 30.12% and 40.80%, respectively, compared with CK. Moreover, Se treatment strengthened the expression correlations among multiple structural genes and transcription factors in the anthocyanin biosynthesis pathway, facilitating the formation of a synergistic regulatory network and thereby promoting anthocyanin accumulation.