Consequences of leaf removal on canopy structure, yield and fruit composition of Touriga Nacional grapevines

Abstract

Defoliation is one of the canopy management operations used as a technic to reduce the leaf area and, consequently, to contribute to improve production. This study aimed to quantify the defoliation effect on canopy density and to evaluate its consequences on yield and fruit composition of Touriga Nacional (Vitis vinifera L.). The field essay was located at Bairrada winegrowing region of Portugal. Three intensity levels of defoliation were compared: non-defoliated control, [T]; leaves removed up to the third node [I₁] and up to the fifth node [I₂]. Defoliation was accomplished about one week after the setting. Defoliation treatments did significantly modify the canopy structure and increased porosity and exposition of the grape bunch. Defoliation treatments had no significant effect on yield and on must soluble solids showing that the remaining leaves were able to guarantee berry development and sugar accumulation in the fruit. However, the anthocyanins and the intensity of color were increased by the defoliation.