Leaf removal, vine physiology and wine quality in cv. Negroamaro (Vitis vinifera L.)

Negroamaro has a very dense canopy. Farmers improve the bunch microclimate by removing leaves and laterals in that zone. As a consequence, clusters are exposed to a very high summer irradiance and are susceptible to sunburn. In order to individuate a best defoliation practice for Negroamaro, the effects on canopy microclimate, leaf functioning, berry and wine composition of three treatments were compared: i) cluster zone farm hand defoliation (FD), ii) cluster zone low intensity mechanical defoliation (MDl), iii) hand canopy defoliation (CD) removing the main leaf and the lateral shoot, at alternate nodes, from the canopy base to the top. Treatments were imposed at berry set. FD removed about 63 % of the total vine leaf area, MDl about 32 %, CD about 48 %. In late June, the shade at the cordon level was almost the double in MDl compared to both FD and CD. At veraison, the photosynthetic rate was higher in FD and CD than in MDl, while stomatal conductance and leaf transpiration did not change significantly. At veraison, the berry internal temperature, measured when the air temperature reached the maximum value (40 °C), was very proximal to this value, independently from the skin color (still green or blue) or the defoliation treatment. Also cluster sunburn damages did not differ among treatments. Compared to FD, the grape yield increased by 16 % in CD and 35 % in MDl. Wine alcohol and phenol content, as well as the anthocyanin content, were higher in FD and CD. The tasting panel preferred FD wines for color and CD wine for flavor.