Mestrado em Viticultura e Enologia - Instituto Superior de Agronomia - UL ; With the goal to improve the characteristics of the grapes, a Cabernet sauvignon vineyard in Maule valley (Chile) was subjected to 5 different typologies of defoliation compared with a control not defoliated. Different timing and quality of defoliation were analysed. It was also compared a kaolin based product to reduce the warming effect of the direct light on the clusters. The study of the canopy, through the point quadrat and the leaf area analyses, gave objective parameters and enabled to have a repeatibility on the years. The amount of light in the canopy and the temperature of the clusters were registered for each treatment in three different occasions. At the harvest the berries were counted and divided according the dehydration to understand the damage done by the sun. The influence of the light and the temperature was studied on the chemical composition of the musts of the vintage 2016 and on the wines of the vintage 2015 to find the best correlation between the solar exposition and the quality parameters of the grapes as the flavonoids. The 2015 wine resulted from the same trial was also sensory analysed by a panel to find additional differences between the treatments. If on one hand, the solar light allows to diminish the quantity of green aromas and to improve the chemical characteristics, an over-exposition could be dangerous for the grape. The aim of this study was to find the right compromise to have the benefit of the light without the damage of the heat. According to this research a total defoliation of the cluster zone during the veraison could be a damage for the yield and the sensory characteristics of the wine. On the other hand the “no act” philosophy of the control doesn’t seem a valid solution because it has the worst sensory results. Seems that in this South American context, the best solution could be a treatment that allow the exposition to the light of the cluster avoiding the hottest hours of the day and limiting the warming of the berries ; N/A