Separation of Sunlight and Temperature Effects on the Composition of Vitis vinifera cv. Merlot Berries

Anthocyanin and phenolic profiles of berry skins from Vitis vinifera cv. Merlot in the Yakima Valley of Washington were influenced by sun exposure and temperature in 1999 and 2000. Growing degree days (base 10°C) accumulated between veraison and harvest were lower in 2000 than in 1999. Total skin monomeric anthocyanin (TSMA) concentrations were higher in 2000 than in 1999 in any given treatment. Berry temperature was increased as much as 13°C above ambient and shaded cluster temperatures when clusters were exposed to sunlight, regardless of aspect for north-south oriented rows. However, maximum fruit temperatures were higher for clusters on the west side of the canopy because ambient temperatures were higher…