Drought stress has become a limiting factor for viticulture with climate change. The influence of arbuscular mycorrhizal fungi (AMF) on grapevine Vitis vinifera L. cv. Ecolly’s leaf water content, chlorophyll concentration, photosynthesis activity, and chlorophyll fluorescence under drought stress was studied in the greenhouse. The experiment was designed as a randomized complete block with four treatments: AMF colonization, well-watered; non-AMF colonization, well-watered; AMF colonization with drought stress; and non-AMF colonization with drought stress. The grapevines inoculated with mycorrhiza had a higher water content in the leaves and higher chlorophyll concentration under drought stress than those without mycorrhiza inoculation. AMF colonization increased the dry biomass of shoots and roots, photosynthetic rate, stomatal conductance, and transpiration rate and decreased intercellular CO₂ concentration. Mycorrhizal grapevines had higher non-photochemistry efficiency, higher photochemistry efficiency, and higher actual quantum yield than non-mycorrhizal grapevines. The results show that AMF alleviated the negative effects of drought stress on grapevines. The alleviation improved leaf water status, chlorophyll concentration, and photosynthetic capacity. Altogether, the results of our study indicate that AMF inoculation has the potential to protect grapevines under drought stress.

Background and Aims. Drought harms the growth and productivity of grapevines; it thus poses a major threat to the development of viticulture in the background of ongoing climate change. Arbuscular mycorrhizal fungi (AMF) can be used to enhance the resistance/tolerance of plants to environmental stress. The effects of AMF on the osmotic regulation, antioxidant substances, and expression of drought-responsive genes in the grapevine Vitis vinifera L. cv. Ecolly were studied. Methods and Results. The experiment was conducted in a greenhouse in a completely randomized block design with four treatments: AMF colonization, well-watered; non-AMF colonization, well-watered; AMF colonization with drought stress; and non-AMF colonization with drought stress. The concentration of sucrose and proline in the leaves was higher in mycorrhizal grapevine than in nonmycorrhizal grapevine under drought stress. The concentration of malonaldehyde, hydrogen peroxide, superoxide anion, and glutathione and the activity of superoxide dismutase and peroxidase activity in leaves were higher in mycorrhizal grapevine than in nonmycorrhizal grapevine under drought conditions. AMF inoculation affected the expression of drought-responsive genes. Mycorrhization upregulated the expression of VvNCED, VvP5CS, VvSIP, VvPIP1;2, and VvTIP2;1 genes under drought stress. Conclusions. AMF could reduce the harm caused by drought stress by regulating osmosis, antioxidant activities, and the expression of key drought-responsive genes and aquaporin genes. Significance of the Study. This work provides insights into the physiological and biochemical activities influenced by AMF on grapevine under drought stress.