Respuesta vegetativa y productiva de Vitis vinifera L. cv Tannat A la práctica de deshojado en diferentes momentos fenológicos del ciclo

During the 2018-2019 harvest, an experiment was carried out with the aim of evaluating the aim of evaulating the effect of leaf removal by the effect of defoliation by manual defoliation at different phenological moments of the grapevine cycle. To evaluate its influence on the microclimate of the cluster, the vegetative expression of the plants, the yield components and the chemical composition of the grapes at harvest were analysed. The experiment was carried out in a vineyard of the cv.Tannat/SO4 (clone 398), with SO4 rootstock, trained on a VSP system (Vertical Shoot Positioned) with bilateral Guyot pruning, located in a commercial vineyard in the town of Juanico, department of Canelones. The defoliation treatments were carried out at pre-flowering (DPF), at fruit set (DC) and at veraison (DE) and were compared with a control without defoliation (TC). The statistical design was a randomised complete block with three replicates and the experimental unit was seven plants. Defoliation was performed manually at the cluster level with an intensity of 70% for DPF and 20% for DC and DE. Defoliation changed the composition of the canopy and thus the microclimate where the bunches were exposed. Defoliation resulted in a 20% reduction in yield compared to the control. In terms of bunch compactness, DPF resulted in fewer berries per bunch, resulting in less compact bunches. The defoliation practice improved the vegetative-productive balance of the plants, which showed a shift towards the vegetative component. With regard to the grape polyphenolic evaluated at harvest, defoliation at fruit set (CD) favoured the concentration and accumulation of potential and extractable anthocyanins compared to the control.