Effects of regulated deficit irrigation (RDI) on grape composition in Monastrell grapevines under semiarid conditions

The influence of two pre-veraison and post-veraison regulated deficit irrigation (RDI) strategies on yield and grape quality was analyzed during a two year period for mature grapevines (cv. Monastrell) in Southeastern of Spain. Three irrigation treatments were applied: T1 control treatment which was irrigated at 60% ETc for the full season (without water stress), applying 319 mm per year; RDI-1 irrigated equal to the control, except from fruit set to harvest (early June-mid –September) where 50% respect to the control was applied and post-harvest (mid-September-end of October) where 75% respect to the control was applied; the water quantity applied in this treatment was 206 mm per year. RDI-2 irrigated equal to the control except from fruit set to harvest where 25% respect to the control was applied and post-harvest irrigated at 75%, applying 157 mm per year. The severity of water stress was characterized by measurements of midday xylem water potential and photosynthesis rate. The grape quality parameters (º Brix, berry weight, titratable acidity, pH, malic, tartatic, color intensity and anthocyanins and polyphenols contents) were also analyzed at harvest. The influence of water stress in different phenological stages on grape quality and the relationship between berry size, fruit quality and level of water stress was analyzed.