Preveraison Water Deficit Accelerates Berry Color Change in Merlot Grapevines

In red varieties, berry color change from green to red is one of the first events associated with ripening and is often used as an indicator of veraison by viticulturists. Water deficit can accelerate ripening and increase pigment accumulation in the berry skin. The impact of water deficit on the timing and progression of berry color change in the vineyard has been largely overlooked. Here we present three years of observations (2011 to 2013) on the progression of color change in Merlot vines subjected to water deficit (WD) or irrigation (C) regimes. Water deficit did not affect the date at which berries started changing color in 2011 and 2012, but pigmentation began three days earlier in WD than in C vines in 2013. Water deficit accelerated pigmentation in all three years and WD berries completed color change five days earlier than C berries on average.