Effects of pre-bloom defoliation (hand versus mechanical) on gas excange, yield components and must composition in Sangiovese (Vitis vinifera L.).

Recent trials on Sangiovese vines have shown that hand defoliation of shoot basal leaves at pre-bloom is effective in reducing fruit-set and yield, leading to better grape quality composition. This trial was designed to compare pre–bloom hand (HD) and mechanical (HD) defoliation on yield and grape composition of Sangiovese spur pruned cordon trained vines, as compared to non defoliated ones (C). In the HD treatment, the first six basal leaves of each shoot were removed whereas in the mechanically treated vines about half of the leaf area was removed by the machine from the basal part of the shoots. However, total leaf area per shoot at harvest did not differ among treatments. Fruit-set percentage, yield per shoot, cluster and berry weight were lowered by both types of defoliation. Leaf-to-fruit ratios in HD and MD were higher than the control because the source loss was more than compensated by yield reduction. Grape composition as soluble solids and total anthocyanins improved with both defoliation treatments. Hand pre-bloom treatment confirmed its effect on yield reduction and on improving crop quality traits. Mechanical pre-bloom defoliation maintained most of the advantages linked to the hand leaf removal.