MANUAL AND MECHANICAL LEAF REMOVAL IN THE BUNCH ZONE (VITIS VINIFERA L. 'NERO D'AVOLA'): EFFECTS ON PLANT PHYSIOLOGY, VEGETATIVE PARAMETERS, YIELD AND GRAPE QUALITY IN A WARM AREA

Mechanical and manual leaf removal of Nero d Avola vines were carried out in a commercial vineyard in Sclafani Bagni area, Sicily (South Italy), in the 2007 growing season. Rows were North East-South West oriented and vines were spur pruned and non-irrigated. The aim was to investigate the effects of two different ways of defoliation on plant physiology, vegetative parameters, yield and grape quality in a warm temperature area. Fruit zone defoliation consisted of mechanical (MLR) and hand leaf removal (HLR), applied either to both sides of the canopy (Northweast and Southeast). These treatments were applied when the berries had reached pea size and compared to a non-defoliated treatment (control). Hand and mechanical leaf removal caused different and significant reduction in leaf area per shoot modifying leaf-to-fruit ratio. Different vegetative activity was showed among the treatments during the vegetative season (from pea size to harvest). Consequently, differences in canopy architecture were measured at pea size and harvest. Photosynthetic activity of primary leaves was higher in leaf removal treatments than in non-defoliated. In HLR must sugar (°Brix) tended to increase during ripeness process, but at harvest no significant differences among treatments were found. Skin total anthocyanins was lower in HLR and the control vines showed the highest values. Leaf removal had effect on variability between the two canopy sides (Northeast/Southwest) for total anthocyanins and flavonoids. In this study leaf removal at pea size did not modify significantly grape quality of Nero d Avola .