Foliar Zinc and Potassium Applications Enhance Fruit Quality and Modulate Pungency Gene Expression in Urfa Pepper (Capsicum Annuum L.)

Abstract

BackgroundUrfa pepper (Capsicum annuum L.), locally known as isot, is a traditional and economically significant landrace cultivated widely in T & uuml;rkiye for its pungency, aroma, and vibrant color. However, there is limited information on how nutrient management influences its fruit quality and pungency at the molecular level.MethodsThis study investigated the effects of foliar-applied zinc sulfate (7.5 mg L--(1)), potassium sulfate (550 mg L--(1)), and their combination on the isot cultivar A-Z-30 F1 under greenhouse conditions. Treatments were applied at three phenological stages, and physiological (chlorophyll index, biomass, relative leaf water content), biochemical (Brix, pH, color), and molecular traits (capsaicin, dihydrocapsaicin, vitamin C content, and expression of Kas, pAmt, PAL, AT3 genes) were evaluated.ResultsZinc application markedly improved fruit color attributes (a* and chroma), Brix content, and dihydrocapsaicin levels. Both Zn and K enhanced chlorophyll index and leaf biomass, although Zn alone decreased biomass. Notably, potassium upregulated AT3 gene expression, while Zn and Zn + K treatments downregulated Kas, pAmt, and PAL. No significant changes were observed in capsaicin or vitamin C content.ConclusionThis study is the first to demonstrate that foliar applications of zinc and potassium significantly influence fruit quality parameters and modulate the expression of capsaicinoid-related genes in Urfa pepper. These findings offer important insights for optimizing nutrient management practices to enhance the biochemical composition and genetic expression profiles of traditional pepper cultivars.