Mycorrhizal symbiosis improve fruit quality in Tempranillo grapevine sensitive to low-moderate warming

An adequate clonal selection could help the adaptation of Vitis vinifera cv. Tempranillo to warming. Moreover, the resilience of Tempranillo to elevated air temperatures increases when associated with arbuscular mycorrhizal fungi (AMF). Our objective was to assess if mycorrhizal association can counteract the deleterious effect of elevated temperatures on plant performance and fruit quality in clones (CL) highly sensitive to warming. Fruit bearing cuttings of Tempranillo CL-843 were cultivated under greenhouse conditions. Assay included plants inoculated (+M) or not (-M) with AMF and grown at either 24/14 degrees C or 28/18 degrees C day/night air temperatures. Elevated temperatures shortened the period between fruit set and veraison in both -M and +M plants and also the period between veraison and maturity in +M plants. Photosynthetic rates were higher under warm tem- peratures irrespective of mycorrhizal inoculation, but sugars and proteins in leaves decreased in-M plants under these environmental conditions. Warming induced the accumulation of Ca, P, Cu and Mn in leaves of all plants and those of Mg and Zn in a greater extent in +M plants. Only in +M plants mature berries maintained the balance of sugars to organic acids and increased the Arg-to Pro-ratio under elevated temperatures. The associ- ation of Tempranillo with AMF may result in a more adequate source of N for yeasts during the must fermen- tation process and could mitigate the increased pH and ethanol levels found in the wines elaborated with grapes developed under low-moderate warming. However, extrapolating these findings to fields in the Mediterranean region or areas subjected to intense warming and frequent heatwaves deserves further study.