Describing the ultra violet light radiation environment of the grape bunch

Abstract

In recent years the focus of much research has turned to the influence of light and heat loads on wine grape quality. Findings over the past years have illustrated negative influences of excessive bunch sunlight exposure and high fruit zone temperatures, impacting on colour development, accumulation of secondary metabolites and berry sunburn and skin integrity. Importantly, berry ultraviolet radiation exposure – particularly to UVB - may enhance the accumulation of compounds such as flavonols, but may also have negative impacts such as berry sunburn. Sophisticated equipment is available for the measurement of temperature and visible light in very small spaces however measurement of UV radiation has until now required quite cumbersome light meters. In this project we have utilised a system for measurement of UVB exposure which comprises small films of polysulphone, sensitive to wavelengths shorter than 330 nm. These films, measuring 3 cm by 3cm, were applied to Cabernet sauvignon bunches in a VSP canopy from veraison to harvest during the 2010 ripening season. Bunches were situated in the shaded canopy interior and in the west facing side and the east facing side of a N-S running row, and films positioned at the bunch top, bottom and north, east, south and west sides of the bunches. The object of this project was to describe the UV environment of the grape bunch at different positions in the canopy. Results of this project will be presented at the AWITC.