Influence of Early Leaf Removal on Flavonoid Accumulation and Antioxidant Capacity in Merlot (Vitis vinifera L.) Berry Components

Cool-climate viticulture regions limit the accumulationof color-specializedmetabolites, such as proanthocyanidins (PAs), total non-extractablePA (NEPA), anthocyanins (TA), and flavonoids in red wine cultivars.This study aimed to evaluate the accumulation of flavonoids and antioxidantcapacity in Merlot berry components such as whole berries, skins,and seeds, after an early leaf removal (ELR) intervention, a managementpractice with proven benefits to increase sunlight and temperatureexposure in grapevines. Pre-bloom manual leaf removal (PB-MA) andpre-bloom mechanical leaf removal (PB-ME) treatments were applied,and color-specialized metabolites were followed through ripening (at33, 56, 70, 96, and 105 days after bloom). The ELR treatments stronglymodulated PAs, while NEPA accumulation differed by tissue type. Wholeberries and skins showed higher capacity (DPPH and FRAP) in both ELRtreatments at harvest. Also, PB-ME treatment enhanced the accumulationof TA, confirming that ELR significantly enhances the accumulationof color-specialized metabolites in Merlot cultivated in cool climateregions.