The critical stages of grapevine breeding projects involve the identification and exploration of drought-tolerant cultivars, as well as the optimization of plant material selection, to effectively maintain grape production under drought stress. The results of the present study revealed significant differences among all physiological, biochemical, and anatomical responses to moderate drought stress in 20 grapevine cultivars. Drought stress resulted in a significant decrease in relative water content (15%) and soluble proteins (47%), accompanied by alterations in stem and root anatomical parameters. Additionally, it led to elevated levels of ion leakage (70%), malondialdehyde (159%), hydrogen peroxide (75%), proline content (94%), soluble carbohydrates (53%), phenolic compounds (89%), and enzymatic antioxidants i.e. catalase, ascorbate peroxidase, peroxidase, and superoxide dismutase by 108, 88%, 87, and 79, respectively. Moreover, significant associations were observed among these characteristics. Principal component analysis (PCA) revealed that the six and four major components affecting traits explained 78.5 and 76.5% of the total variance in traits under control and drought conditions, respectively. PCA also identified the most suitable criteria for the identifying of cultivars under moderate drought conditions, encompassing traits such as water content, soluble proteins, proline, soluble carbohydrates, phenolic compounds, catalase, ascorbate peroxidase, peroxidase, superoxide dismutase, stem xylem area, stem phloem area, root cross-sectional area, and root xylem diameter variables. Furthermore, hierarchical cluster analysis with a heatmap categorized grapevine cultivars into three groups under drought conditions. Based on our comprehensive findings, it can be concluded that ‘Rashe’, ‘Khalili Sefid’, ‘Yaghuti’, and ‘Laal Ghermez’ exhibit the highest level of drought-tolerant cultivars.
