Integrative physiological, biochemical, and gene expression analysis reveals methyl jasmonate–mediated enhancement of drought tolerance in grapevine rootstocks

Drought stress is one of the major environmental constraints limiting grapevine growth, physiological performance, and productivity in many viticultural regions. Rootstocks play a crucial role in improving drought tolerance; however, their physiological and molecular responses to water deficit remain insufficiently understood. In the present study, six grapevine rootstocks (SO4, 3309 M, Kangzhen 3, 5BB, Beida, and 101–14) were evaluated under control, drought, and drought combined with methyl jasmonate (MeJA) treatments to investigate their morpho-physiological, biochemical, and molecular responses to water deficit. Drought stress significantly reduced vegetative growth parameters, including plant height, stem diameter, internode number, leaf number, and biomass accumulation, and decreased photosynthetic efficiency and relative water content. In contrast, drought conditions increased oxidative stress markers, including hydrogen peroxide and malondialdehyde, and led to the accumulation of osmolytes, including proline, soluble sugars, and soluble proteins. Antioxidant enzyme activities, including superoxide dismutase, catalase, Glutathione Peroxidase, and ascorbate peroxidase, were also enhanced as part of the plant defense response. Foliar application of MeJA (100 μM) effectively alleviated drought-induced damage by improving plant growth, strengthening osmotic adjustment, nutrient retention, and enhancing antioxidant defense systems. Moreover, MeJA significantly upregulated the expression of drought-responsive genes ( VvNAC8, VvNAC17 , and VvNIP1.1 ) and jasmonate signaling genes ( VvJAZ, VvJMT , and VvMYC2 ), indicating activation of molecular pathways associated with stress tolerance. Correlation analysis, cluster heatmap, and principal component analysis revealed strong relationships among growth traits, physiological parameters, biochemical responses, nutrient status, and gene expression patterns, highlighting coordinated mechanisms of drought adaptation. Overall, the results indicate clear differences in drought tolerance among the evaluated rootstocks, with SO4 and 3309 M showing higher tolerance, Kangzhen and 5BB exhibiting moderate tolerance, and Beida and 101–14 being relatively sensitive to drought stress. These findings provide valuable insights for selecting drought-resilient rootstocks and for applying MeJA as a potential strategy to improve grapevine performance under water-limited conditions.