Assessment of biochemical and physiological responses of several grape varieties under water deficit stress

Grapes ( Vitis vinifera L.) are a crucial crop globally, particularly in arid regions where water scarcity is a concern. This study investigated the physiological and biochemical responses of several grape varieties to water deficit stress. The research was conducted within the controlled environment in a factorial experiment with a completely randomized setup comprising three replicates. The first variable, irrigation, consisted of two levels: a 15-day water stress and a control group receiving irrigation maintained at field capacity. The second variable was the grape variety, encompassing a total of 15 commercial varieties. Water deficit stress reduced chlorophyll content in all varieties. 'Bidaneh Sefid' variety had the highest chlorophyll content (8.76 mu g.g-1 FW). Furthermore, this variety demonstrated superior relative water content under stress (79.22%), whereas 'Keshmesh' variety exhibited such performance under normal conditions. The results illustrated a proline content range spanning from 48.48 to 61.01 mu mol.g-1 FW. Notably, water deficit stress resulted in elevated proline content, with the highest mean observed in the 'Khalili' variety under such stress conditions. Water scarcity impacted grape traits significantly: reduced chlorophyll, relative water content, increased leakage, higher proline, carbohydrate, anthocyanin, and phenols, with varying antioxidants. 'Bidaneh Sefid' variety had most chlorophyll, 'Khalili' highest proline under stress, 'Maskeh' variety excelled in carbohydrate. 'Fakhri', 'Filam Seedless', 'Shiregi' varieties topped anthocyanins; 'Khalili' variety showed best antioxidant activity. The findings highlight specific grape varieties that exhibit desirable traits under water deficit stress, such as higher chlorophyll content, proline accumulation, and carbohydrate accumulation. These varieties could serve as valuable genetic resources for breeding programs aimed at developing drought-tolerant grape cultivars. Additionally, the identification of varieties with enhanced antioxidant capacity and anthocyanin levels holds potential for the development of grape-based products with possible health benefits.