Influence of leaf removal on grape, wine and aroma compounds of Vitis vinifera L. cv. Merlot under Mediterranean climate

Merlot is one of the most cultivated cultivars in the world since it easily adapts to different climatic conditions. Leaf removal (LR) is commonly used for red berry varieties but in cold wine-growing areas and nothing has been reported on the effects of LR on Merlot cultivated under Mediterranean climate. The aim of the research is to evaluate the influence of this technique on grape and wine quality as well as wine aroma potential of Merlot cultivated in Sicily. Vines were subjected to LR for two consecutive years, and productivity and chemical parameters were monitored in grapes, whereas chemical composition and volatile aroma compounds, analyzed by gas chromatography mass spectrometry, were monitored in wines. LR positively influenced the plant yield, increased the sugar content and decreased the acidity in grapes at harvest. The wines of the defoliated treatment showed a higher content of total polyphenols and anthocyanins, higher color intensity, and lower color hue. Merlot wines obtained under Mediterranean climate were characterized by a high amount of esters and varietal aromas and the content of most of volatiles were even increased by the LR with positive effects on the aroma potential of Merlot wines. The vintage affected almost all the studied parameters with the warmer and dryer vintage enhancing the LR effects on grapes and wines. This is of great interest in the light of the climate changes towards the global warming and the increasing aridity of the Mediterranean area.