Effects of leaf removal and applied water on berry flavonoid accumulation of (vitisviniferal.) merlotberry in hot climate

The relationships between variations in grapevine (Vitis viniferaL.) fruit zone light exposure and applied water amounts and the resulting berry flavonoid composition were investigated in a hot climate.The experimental design involved the application of mechanical leaf removal (control, pre-bloom, post-fruit set) and differing water stress [sustained deficit irrigation (SDI) and regulated deficit irrigation (RDI)].Flavonol and anthocyanin concentrations improved with pre-bloom leaf removal.Post-fruit set leaf removal increased total proanthocyanidins in both years while no effects were observed with irrigation treatments.The mean degree of polymerization of berry skin proanthocyanidins increased in both years with the post-fruit set leaf removal while irrigation had no effect. Proanthocyanidin trihydroxylation and conversion yield were consistently greater with post-fruit set leaf removal. Seed proanthocyanidins concentration and mean degree of polymerization were rarely affected by leaf removal or irrigation treatment. The application of post-fruit set leaf removal, regardless of irrigation regime consistently increased the proportion of skin proanthocyanidins, while seed proanthocyanidin proportions were greater with no leaf removal regardless of irrigation treatment. The study provides fundamental information to viticulturists and winemakers on how to manage monomeric phenolics and polymeric proanthocyanidins composition of red wine grape in hot climate.