Irrigation Strategy Affects Quantitative and Qualitative Vine Performance of ‘Italia’ Table Grape

Table grape vines (Vitis vinifera L.) grown in arid regions require irrigation to achieve optimum fruit yield and quality. Quality is usually considered as a combination of appearance, physical and chemical characteristics at harvest and during storage. Irrigation management, undoubtedly, represents a key strategy to optimize vine performance, in relation to both quantitative and qualitative response. The objective of this research was to evaluate the effects of three different water regimes on berry growth and fruit quality of 'Italia' table grape. To reach this aim, a field trial was carried out on an experimental vineyard located in Apulia region, on 'Italia' table grape (grafted on SO4 rootstock), trained to "tendone" trellis system. Three watering regimes were compared: V1, V2 and V3 (corresponding to 120, 80 and 40% of water lost by evapotranspiration (excluding effective rainfall)). Irrigation was scheduled using the "water balance" method starting after berry set. During the growing season, berry development and ripening kinetics were monitored; stem water potential and stomatal conductance were measured at different phenological stages in order to evaluate crop water status. At commercial harvest, the main quantitative and qualitative yield parameters were determined. Water stress was evident since fruit set, as shown by midday stem water potential and stomatal conductance, and has significantly affected berry growth, ripening kinetic and fruit yield. Compared to V1 treatment, a yield reduction of 12 and 32%, due to both bunch size and berry weight, was observed for V2 and V3 treatments respectively.