A consortium of arbuscular mycorrhizal fungi and plant growth-promoting bacteria modulates wine grape ripening and composition under climate change conditions.

If no major changes in CO2 emissions policy take place, atmospheric CO2 and temperature are expected to increase in the coming decades, negatively affecting grape composition. Arbuscular mycorrhizal fungi (AMF) have been reported to increase plant resilience to various stresses. This study aimed to assess whether the association of young grapevines with AMF, co-inoculated with bacteria (PGPRs), can mitigate the effects of climate change on grape composition. Two-year-old Cabernet Sauvignon plants grafted onto R110 rootstock, either inoculated with a consortium of AMF and PGPRs (+M) or with only PGPRs (-M), were exposed to two CO2 levels (ambient CO2, AC, or 700 ppm, EC) and two temperatures (ambient temperature, AT, or ambient temperature increased by 4 °C, ET) in a factorial design (2x2x2). Plants under ET experienced about 5 heat waves and 21 days with maximum temperatures above 40 °C, 2 heat waves and 4 days above 40 °C in AT. ET reduced berry mass, total soluble solids, and acidity in the must; these differences were less pronounced in +M. Grapes under ET had lower concentration of anthocyanins but these were more methylated (malvidins) and coumaroylated, regardless of the CO2 level and AMF inoculation. The concentration of total amino acids and yeast assimilable N decreased under EC, whereas ET decreased the relative abundance of proline. co-inoculation of AMF and PGPRs increased the concentration of total and aroma precursor amino acids, especially under ACAT, and proline abundance, thus partially counteracting the effects of both EC and ET. Co-inoculation of AMF and bacteria helped attenuate some of the effects of climate change on grape berry ripening and primary metabolite composition.