Exogenous abscisic acid application modulates source-sink relationships under a leaf number-regulated production system to improve grape and wine quality in hot-climate regions.

Abstract

Under global warming, wine grapes in hot and arid regions often exhibit sugar-acid imbalance, limited phenolic accumulation, and simplified aroma profiles, constraining wine quality. Leaf retention could regulate canopy microclimate and photosynthetic supply (source), whereas exogenous abscisic acid (ABA) could influence fruit metabolic activity (sink). However, their combined effects on the regulation of grape and wine quality remain unclear. A two-year field experiment (2023-2024) was conducted with 'Marselan' (Vitis vinifera L.) using a two-factor factorial design combining three leaf-retention levels (low, moderate, high) with three ABA concentrations (0, 150, 300 mg/L). Grapes and wines were analyzed for physicochemical traits, phenolics, and volatile compounds. The results indicated that lower leaf retention reduced potential alcohol and increased titratable acidity, whereas ABA promoted phenolic accumulation. Significant interactions between the two factors were observed. High ABA (300 mg/L) promoted phenolic and anthocyanin accumulation under low leaf retention. Moderate leaf retention with 300 mg/L ABA resulted in the highest tannin concentration. Lower leaf retention increased C6 compounds and terpenes. Overall, combining optimized leaf retention with exogenous ABA showed potential to improve grape and wine quality by increasing acidity and promoting phenolic accumulation and aroma composition. This combination may provide a promising approach for quality management of wine grapes cultivated in hot and arid regions.