PHENOLICS DYNAMICS OF BERRIES FROM VITIS VINIFERA CV SYRAH GRAFTED ON TWO CONTRASTING ROOTSTOCKS UNDER COMBINED SALINITY AND WATER STRESSORS AND ITS EFFECT ON WINE QUALITY
Wine regions are getting warmer as average temperatures continue raising affecting grape growth, berry composition and wine production. Berry quality was evaluated in plants of Vitis vinifera cv Syrah grafted on two rootstocks, Paulsen (PL1103) and SO4, and grown under two salinity concentrations (LS:0.7dS/m and HS:2.5dSm-1) in combination with two irrigation regimes (HW:133% and CW:100%), being the seasonal water application 483mm (control, 100%). Spectrophotometer measurements from berry skin during veraison and harvest stages and from “young” wine samples, were indicative of the stressors effect and the mediation of the rootstocks. At veraison (i) total phenolics content were high under LSHW (0.7dSm-1 and high water conditions) for SO4 and PL1103. (ii) Tannins were higher in SO4 under LSHW and in PL1103 under HSCW (2.5dSm-1 and control water conditions). (iii) Higher carotenoids were found at HSCW for both rootstocks. At harvest: (i) total phenolics content decreased dramatically from veraison to harvest stage under high salinity in both rootstocks. Phenolic content decreased by 34% in SO4 and 32% in PL1103. Under LS (0.7dSm-1) total phenolics content decreased by 29% in both rootstocks. (ii) Tannins in SO4 were higher under LSCW (0.7dSm-1 and control water conditions) while in PL1103 were higher under HSHW (2.5dSm-1 and high water conditions). (iii) Carotenoids highly accumulated under HSHW in both rootstocks. In young wine samples: (i) total phenolics content was higher in wines made from berries under HSCW in SO4 while in PL1103 was higher under LSCW treatment. (ii) Tannin content was higher in the wine made from berries under HSHW from SO4 and with berries from PL1103 grafts under LSCW. (iii) For carotenoids the highest content was found in wines made with SO4 under LSCW and with PL1103under HSCW. In conclusion, our results show a clear mediating effect of the rootstock on Syrah berry metabolism and wine quality. This data should be considered when planning the use of reclaimed water in irrigation strategies or when growing plants in saline soils. Moreover, graft tolerance and mediating effects on berry metabolism might not be consistent, requiring a compromise between yield and quality.
Issue: OENO Macrowine 2023
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phenolics, rootstocks, combined stress, wineberry quality