Effects of Water Regimes on Vine Performance and Quality of 'Sublima' Seedless Table Grape Covered with Plastic Film to Advance Grape Ripening

In Southern Italy, vineyards of early seedless table grape are always grown under irrigation and covered with plastic film to advance grape ripening. A trial was carried out in a commercial vineyard located in the Apulia region, on cv. 'Sublima Seedless' trained to “tendone” trellis system. Vines were covered with plastic film and applying different water regimes. The effects exerted by the irrigation regime on vine water status, vine ecophysiological activity and the productive characteristics were investigated. Three watering regimes were compared: WR1, WR2 and WR3 corresponding to 50, 100, and 80% of water lost by evapotranspiration (excluding effective rainfall). Irrigation was scheduled using the “water balance” method, starting after berry set. The radiometric properties of the plastic film were evaluated by means of laboratory tests. Stem water potential was measured at different phenological stages in order to evaluate crop water status. Leaf gas exchange was also measured. 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 has significantly affected berry growth and fruit yield. Leaf gas exchange was more active with WR2 treatment. A yield reduction of 9 and 44%, due to both, bunch size and berry weight, was observed for WR3 and WR1 treatments, respectively, compared to WR2 treatment