Effects of water regime on vine performance and quality of 'Sublima Seedless' table grape covered with plastic films

In southern Italy, early table grape cultivars are irrigated and covered with plastic films in order to advance the ripening and increase the grower net income thanks to the higher price of these grapes on the market. A study was run to evaluate the effects of three different irrigation regimes, corresponding to 100 (V1), 80 (V2), and 50% (V3) of water lost by evapotranspiration, on 'Sublima Seedless' covered with three plastic films: "YELLOW", "NEUTRAL" and "BASF". The plastic film radiometric properties were analyzed by means of laboratory tests. Midday stem water potential (ΨMDS) and leaf gas exchange were measured. The lowest ΨMDS was shown by V3 vines. Close to berry ripening, V1 and V2 vines had similar photosynthetic rates and, moreover, leaf water use efficiency did not change among irrigation treatments. A low statistical interaction between irrigation and plastic films was shown by ΨMDS. V2 and V3 treatments reduced grape yield due to both a lower bunch size and berry weight. Best balance among vegetative growth, grape yield, berry quality and water use was obtained by V2 treatment. Berry carpological traits and composition were affected also by the type plastic cover.