Influence of irrigation strategy and mycorrhizal inoculation on fruit quality in different clones of Tempranillo grown under elevated temperatures

The projected climate scenario for South Mediterranean Europe predicts lower precipitation and higher temperatures that will negatively affect viticulture in the region. The application of moderate deficit irrigation at crucial moments of berry ripening has been found to improve berry quality. Furthermore, grapevine association with arbuscular mycorrhizal fungi (AMF) may improve grapevine's ability to cope with abiotic stresses. Therefore, the aims of this research were: (1) to characterize the response of three clones of Vitis vinifera L. cv. Tempranillo to the combination of different water deficit programs and AMF inoculation under elevated temperatures, and (2) to determine whether AMF inoculation can improve berry antioxidant properties under these conditions. The study was carried out on three fruit-bearing cuttings clones of cv. Tempranillo (CL-260, CL-1089 and CL-843) inoculated (+M) or not (−M) with AMF and subjected to two temperature regimes (24/14 °C and 28/18 °C (day/night)) combined with three irrigation regimes during berry ripening. Irrigation treatments were: (i) water deficit from fruit set to veraison (early deficit, ED); (ii) water deficit from veraison to maturity (late deficit, LD); and (iii) full irrigation (FI). Although each Tempranillo clone seemed to have different abilities to respond to elevated temperatures and water supply, in general, at 24/14 °C the LD treatment performed better than ED. Differences among clones were attenuated at 28/18 °C. In addition, potential benefits of the LD treatment were improved by AMF inoculation. Thus, in all clones the loss of anthocyanins at 28/18 °C detected in −M plants after applying LD did not occur in the +M plants. Moreover, AMF inoculation increased must antioxidant capacity in CL-843 under these environmental conditions. Our results suggest that the implementation of measures to promote the association of grapevines with appropriate AMF for each variety could contribute to optimize effects of irrigation strategy on berry properties under future warming conditions.