Symbiosis with Rhizophagus irregularis improves grapevine rootstock performances under water deficit conditions

Grapevine represents a major crop with crucial socio-economic importance, however, its culture is threatened by climate change, especially drought. Indeed, water deficit has a negative impact on grapevine growth and yield but also impacts fruit and wine quality. To improve grapevine resilience to drought, developing strategies such as symbiosis with Arbuscular Mycorrhizal Fungi could be a promising. We focused on the benefit of using Rhizophagus irregularis DAOM 197198 for improving performances in controlled conditions of two highly 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 deficit 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 on non-stressed plants. Further analysis of mineral nutrition and aquaporin expression revealed contrasting responses between the two rootstocks. Whereas mycorrhization strongly enhanced phosphorus contents 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 induce 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.