Accumulation of proanthocyanins during ripening because of early leaf removal in Merlot ( Vitis vinifera L.) grapevines.

Abstract

Abstract Accumulation of color compounds including proanthocyanidins (PAs) and anthocyanins were evaluated during berry ripening at 33, 56, 70, 96, and 105 Days after bloom (DAB), due to early leaf removal (ELR) treatments in Merlot applied at pre-bloom. Three treatments were used: 1) pre-bloom manual leaf removal (PB-MA), 2) pre-bloom mechanical leaf removal (PM-ME), and 3) undefoliated control (C). Whole berries were separated into their major components (skins and seeds). PAs were determined by vanillin assay and Non-Extractable Polymeric proanthocyanidins (NEPA) methods; Antioxidant capacity was evaluated as the inhibition percentage of DPPH radical and FRAP. Total phenolic content was measured in whole berries, skins, and seeds, while sugars, anthocyanin, and flavonols by HPLC-MS were also analyzed in whole berries. PAs were strongly modulated by the ERL treatments, while NEPA accumulation was different by the type of tissue. Anthocyanin and flavonol contents began to accumulate at 70 DAB (verasion) and increased throughout the berry development. ELR enhanced cluster microclimate conditions, resulting in an increased accumulation of color compounds. These results support the use of PA in addition to anthocyanins and flavanols profile as excellent candidates for studies aiming to modify canopy architecture, with early leaf removal strategies.