Post-Veraison Water Stress and Pruning Level on Merlot Grapevine: Effects on Berry Development and Composition

Abstract

Productivity and wine quality are greatly affected by the growth and make-up of the grapevine berries when harvest time rolls around. The development of fruit traits in grapevines, such as berry size, weight, and volume, and berry composition, including total soluble solids (TSSs), titratable acidity (TA), pH of the grapes, total anthocyanins, and phenolic content and concentration, can be influenced by increasing grapevine productivity through appropriate pruning and watering. Within this framework, the objective of this research was to investigate how berry growth and composition react to the combined influence of pruning intensity and water stress after veraison. The experiment included four different degrees of pruning (severe, standard, light, and minimum) and four different water stressors (none, light, moderate, and extreme) after veraison. With the exception of berry weight, which was affected by the combined impact of pruning level and post-veraison water stress, every parameter has been drastically changed by the interaction. A decrease in berry volume, weight, yield, and TA, along with a rise in total sugar, pH, total anthocyanins, and phenols, are typical results of post-veraison water stress. Pruning levels have a negative effect on berry output per vine, total solids, and pH, while having a positive effect on berry weight, volume, total anthocyanins, and phenols. Specifically, grapevines that were severely trimmed and given enough water produced the most fruit in terms of volume, weight, and tannin content. The TSS and pH of the grape juice were greatest from severely water-stressed, minimally-pruned plants. As the degree of pruning increased from mild to severe, total anthocyanins and phenols increased, but as the degree of water stress increased from zero to extreme, they decreased. However, under extreme water stress, grapevines that had been severely trimmed showed the highest concentrations and contents of total anthocyanins and phenols. Surprisingly, grapevines that were little clipped and given enough water produced more berries per plant, perhaps because there were more nodes on each vine. The volume, weight, yield, and TA of the berries were strongly inversely related to TSS, while pH was positively related to TSS. The fruit production per grapevine was likewise negatively linked with total anthocyanins and phenols. Based on the findings, a potent strategy for achieving berry growth and composition balance is the combined influence of water stress and pruning levels. Although Merlot's berry development characteristics, such as berry output per vine, may decrease, it is crucial to enhance the berry composition since the grapevine is a typical red wine grape.