Responses of four winegrape varieties to managed water stress and partial defoliation in an arid environment

In viticulture, the imposition of managed water deficits is a strategy which has been used to increase both water use efficiency and winemaking quality in arid climates. Partial defoliation early in the season is another innovative practice that may also be used as an aid in regulating yield components and improving fruit quality. The aim of this work was to evaluate the effects of managed water stress and early season partial defoliation on crop yield and quality in two autochthonous (‘Frappato’ and ‘Nero d’Avola’) and two international varieties (‘Syrah’ and ‘Cabernet Sauvignon’) growing in an arid environment. The four treatments were: (i) no leaf removal, un-irrigated, (ii) no leaf removal, irrigated at 30 % of estimated crop evapotranspiration (ETc), (iii) partial leaf removal, un-irrigated, and (iv) partial leaf removal, irrigated at 30 % of estimated ETc. The results confirm the effectiveness of partial defoliation in yield management which leads to smaller clusters. Managed water stress was also an effective strategy for reducing berry size, improving must quality and generally enhancing anthocyanin accumulation.