Crimson Seedless table grape grown under plastic film: ecophysiological parameters and grape characteristics as affected by the irrigation volume

Plastic films used to cover vineyard change microclimate conditions aiming to advance or delay grape maturity according to the table grape marked demand. The capacity of the cov-ering materials to modify the greenhouse microclimate strongly depends on their radiometric properties. The aim of this paper is to study the effect of three watering regimes and of the radiometric characteristics of plastic film used to delay harvest of Crimson seedless table grape grown in the Apulia region (Southern Italy). Crimson Seedless vines trained to “tendone” trellis system were irrigated with different water regimes, from berry set to one week before harvesting, corresponding to about 50% (WR1), 100% (WR2) and 80% (WR3) of water lost by evapotranspiration. After veraison, Crimson Seedless vines were covered with plastic film until grape harvest. Laboratory tests were carried out on the new film in order to evaluate the radiometric properties. Vine water status and leaf gas exchange were as-sessed. At harvest, the yield components and the grape characteristics were analyzed. Vine water status measured under midday conditions showed a moderate improvement for WR3 and WR2 treatments, but leaf temperature decreased and leaf gas exchange increased in WR3 vines. Water availability significantly affected berry growth, inducing the lowest cluster weight in the treatment WR1 that received the lowest watering volumes; also berry diameters were significantly affected by the irrigation treatments. Crop water productivity (grape produc-tion per unit of applied water) decreased from WR1 to WR2 and WR3. The greatest water deficit reduced significantly the total pruning weight per vine, that is an indicator of the vege-tative vigor.