Improving salt stress tolerance in grapevine rootstocks and cultivars through foliar application of ascorbic acid.

Salt stress (SS) significantly limits the productivity of fruit trees, highlighting the need for effective strategies to increase plant resistance. This study aimed to investigate the effects of ascorbic acid (AA) and SS on two grapevine rootstocks, 140Ruggeri (Ru) and 1103Paulsen (Pa), as well as two cultivars, Yaghouti (Ya) and Sultana (Su) The experiment was conducted in pots using three salinity levels (0 mM as control, 25 mM, and 50 mM NaCl) and four concentrations of AA (0 mM as distilled water, 2 mM, 4 mM, and 6 mM). In this study, we evaluated traits related to roots, shoots and leaves, photosynthetic pigments, leaf relative water content (RWC), electrolyte leakage (EL) and compatible osmolytes include total soluble carbohydrates, proline, and glycine betaine. The results indicated that the response of rootstocks and cultivars under SS varied according to stem, root, and leaf traits. The rootstocks Pa and Ru showing the least reduction in morphological traits and photosynthetic pigments and the highest synthesis of compatible osmolytes under SS. In contrast, the Su cultivars was identified as the most sensitive to SS, showing the strongest reduction in RWC, pigments, and osmolyte synthesis. The application of AA effectively alleviated SS, depending on rootstock and cultivar responses. In the rootstocks Pa and Ru, particularly at a concentration of 6 mM AA, was more pronounced in the synthesis of compatible osmolytes. Meanwhile, in the Su, the impact of this treatment was more significant in improving morphological traits and reducing EL under SS. Moreover, multivariate analyses clearly revealed the differentiation of rootstock and cultivar under SS and AA treatment. The findings of this study suggest that foliar application of AA can serve as a promising strategy to alleviate the detrimental effects of SS in grapevine.