Symbiosis With Rhizophagus irregularis Improves Grapevine Rootstock Performances Under Water Deficit Conditions.

Grapevine is a major crop of crucial socio-economic importance; however, its culture is threatened by climate change, particularly drought. Indeed, water deficit has a negative impact on grapevine growth and yield, but also affects fruit and wine quality. To improve grapevine resilience to drought, developing strategies such as symbiosis with Arbuscular Mycorrhizal Fungi could be promising. We focused on the benefits of using Rhizophagus irregularis DAOM 197198 in improving performances in controlled conditions with two widely used rootstocks (41B and SO4) under moderate to severe water deficit. At a field capacity of 14%-40%, SO4 was more affected compared to 41B. Successful functional symbiosis was obtained for the two rootstocks, both in well-watered and water-deficient conditions. Interestingly, colonization with R. irregularis improved growth and photosynthetic parameters in both 41B and SO4, especially under water stress, restoring them to the levels of non-stressed plants. Further analysis of mineral nutrition and aquaporin expression revealed contrasting responses between the two rootstocks. Whereas mycorrhization strongly enhanced phosphorus concentration in both 41B and SO4 roots and leaves, the overall beneficial effects of the symbiosis on mineral nutrition were more pronounced in SO4. In contrast, the expression of VvPIP2.1, a highly water-permeable aquaporin involved in root hydraulic conductivity, was increased in mycorrhized roots of 41B but repressed in SO4. This study emphasizes that interaction between AMF and grapevine induces contrasting effects on plant nutrition depending on the rootstock genotype, and that mycorrhizal inoculation could be of interest in the case of drought-sensitive rootstocks.