Exogenous alpha-lipoic acid treatments reduce the oxidative damage caused by drought stress in two grapevine rootstocks.

Drought represents the predominant and most critical abiotic stress challenge within the domain of viticulture, necessitating the identification and application of efficacious strategies to ameliorate its deleterious effects. In the contemporary realm of abiotic stress management, the deployment of α-lipoic acid (α-Lipo), known for its antioxidant capabilities, as an exogenous treatment has been investigated for mitigating various abiotic stresses in numerous plant species, yet a detailed exploration of its efficacy in alleviating drought stress in grapevines remains to be conclusively determined. This study aimed to elucidate the adaptive mechanisms against drought stress by examining the effects of different α-Lipo concentrations (0, 1, 25 and 50 μM) applied on the foliar under well-irrigated and drought conditions on American grapevine rootstocks '1103 P' (drought tolerant) and '3309 C' (drought sensitive). Our findings revealed that the efficacy of α-Lipo varied significantly depending on rootstock type and irrigation status. 1103 P rootstock treated with 1 μM α-Lipo under well-irrigated conditions showed greater positive effects on growth traits, photosynthetic and osmotic parameters. In contrast, in rootstock 3309 C under the same conditions, the highest effects were obtained at 25 and 50 μM α-Lipo concentrations. Under drought stress conditions, 50 μM α-Lipo treatment improved physiological parameters (chlorophyll content, proportional water coverage and stomatal conductance), proline content and antioxidant enzyme activities (SOD, CAT and APX), while reducing electrolyte leakage and MDA levels in both rootstocks, showing a strong potential to increase oxidative stress tolerance and sustain plant growth. Heatmap visualization analysis confirmed the data obtained from Principal Component Analysis (PCA) and revealed that 1103 P treated with 50 μM α-Lipo under drought stress conditions exhibited superior physiological performance compared to 3309 C under the same conditions. This indicates the importance of potential rootstock differences in stress adaptation or α-Lipo uptake efficiency. These findings suggest that α-Lipo holds promise as an eco-friendly, natural bio-stimulant for use in arid environments, contributing to the advancement of sustainable agricultural practices in the foreseeable future.