Assessment of sunburn damage in Chardonnay grapes in relation to leaf removal timing

Sunburn damage commonly appears as browning of the berry surface when these are directly exposed to sunlight in combination with high temperatures and ultraviolet radiation. Factors such as variety, berry developmental stage, ambient temperature, water availability and viticultural practices (i.e. defoliation) modulate the intensity of symptoms. Leaf removal is a common practice in cool viticultural areas to reduce disease pressure. However, overexposure of bunches can lead to a higher degree of sunburn. Previous research indicates that if performed before véraison, defoliation leads to an early accumulation of photoprotective compounds such as the flavonoids and the carotenoids which would protect the berry from UV damage and reduce the intensity of sunburn but evidence is lacking. The aim of this study was to evaluate the effect of leaf removal timing on the incidence of sunburn as well as on the concentration of photoprotective compounds.