EFFECTS OF IRRIGATION VOLUME ON QUANTITATIVE AND QUALITATIVE PERFORMANCE OF ORGANIC "ITALIA" TABLE GRAPE GROWN IN SOUTHERN ITALY

In Europe there is an increasing consumer demand for residue-free, organically grown table grapes. Organic table grapes cultivation, however, is very delicate and experience to advice organic growers is still quite lacking. Table grapes vines (Vitis vinifera L.) are always grown with irrigation in regions, characterized by low rainfall and a high evaporative demand, as it occurs in Apulia region (Southern Italy). Moreover, only limited guidelines are available for managing irrigation to obtain optimum balance among vegetative growth, yield, quality in organic table grape production of Southern Italy. The objective of this study was to evaluate the effects of two irrigation regimes on ‘Italia’ table grape variety grown in Apulia according to organic European Community rules. In 2010, Italia grapevines grafted onto 1103 Paulsen and trained to tendone system received two irrigation treatments: 80% and 100% of estimated vine evapotranspiration ETc. The number of buds, shoots and clusters per vine was uniformed. Vine water status and stomata conductance were measured at berry set, during berry growth and at grape ripening. At harvest, yield components and berry quality were assessed. As expected, vines that received the lower irrigation volume showed the worse water status and stomata conductance and reduced the leaf area expansion. At commercial harvest (4th October), grapes produced by 80% ETc irrigated vines reached a slightly lower sugar concentration, but SST/AT ratio did not change. The grape yield was reduced as a result of a lower berry number per cluster and a lighter berry weight. Vines irrigated at 80% of ETc were less vigorous, as showed by their lower pruning weight; however, the Ravaz index did not change between treatments.