Effects of solar ultraviolet radiation and canopy manipulation on the biochemical composition of Sauvignon Blanc grapes

Abstract

Background and Aims:New Zealand is exposed to relatively high solar ultraviolet (UV) radiation; such high irradiances of UV radiation having the potential to change the biochemical composition of plants. The aim of this study was to investigate the effects of UV radiation and the role of canopy leaves on berry biochemical composition in Vitis vinifera var. Sauvignon Blanc. Sauvignon Blanc is the major grape variety grown in New Zealand. Methods and Results: Leaves were removed from around the fruiting zones of vines and screens that altered UV radiation exposures were placed over the grape bunches. Samples taken throughout development were analysed for changes in total phenolic compounds (including flavonols), amino acids and methoxypyrazines. Total phenolic compounds increased substantially in response to UV-B exposure and this was reflected in changes taking place within the skins of the berries. Flavonol levels were determined by UV-B radiation exposure and accumulated to maximum concentrations at veraison, subsequently declining to harvest. UV radiation did not have a significant effect on the majority of amino acids or methoxypyrazine concentrations. The most noticeable change in amino acid and methoxypyrazine accumulation was caused by the presence of leaves over the fruiting zone, retaining these leaves maintained significantly higher concentrations in the berries at harvest. Conclusions: UV-B radiation determines the composition of flavonols in the skins of grapes. Amino acid and methoxypyrazine concentrations are not predominantly determined by UV-B, but retention of leaves over the fruiting zone promotes their accumulation in berries. Significance: Canopy manipulations are routinely used commercially in the vineyard to help control vigour and reduce disease pressure. The findings presented here are important for viticulturists to understand how management of the vine leaf canopy can determine the biochemical composition of the grapes and can therefore, ultimately affect wine quality. Gregan et al.Effects of ultraviolet on grape berry biochemistry 227

Effect of grape bunch sunlight exposure and UV radiation on phenolics and volatile composition of Vitis vinifera L. cv. Pinot noir wine

“…Similarly, the UV exposure increased wine colour density, anthocyanin, total pigments, total phenolics and tannins by respectively 79%, 106%, 66%, 85% and 202%. These results are likely to be due to the increased flavonol and flavonoids due to the activation of genes of the phytopropanoid pathway in grape berries simulated by UV radiation (Gregan et al, 2012). However, some researchers reported that ambient UV radiation had no effect on total anthocyanins in grape berries (Keller & Torres-Martinez, 2002;Spayd et al, 2002).…”

“…In this study, polycarbonate and acrylic sheet were used to block or transmit UV radiation, respectively, using the method of Gregan et al (2012). These two covering materials could transmit most of photo-synthetically active radiation, while they had considerably different transmission rate in UV region.…”

“…These two covering materials could transmit most of photo-synthetically active radiation, while they had considerably different transmission rate in UV region. Polycarbonate sheet excludes the transmission of all UV wavelengths, whereas acrylic sheet can transmit all UV wavelengths (Gregan et al, 2012). Actual differences in photosynthetically active radiation (PAR) between the treatments were not measured.…”

Phenology and grape ripening characteristics of cv Tempranillo within the Ribera del Duero designation of origin (Spain): Influence of soil and plot characteristics

“…Thus, temperature plays and important role on flavonoid development (Huglin and Schneider, 1998), anthocyanin concentrations (Coombe, 1987;Tarara et al, 2008), proanthocyanidin (Cohen et al, 2012Zamora, 2003 and on various aroma compounds (Duchêne and Schneider, 2005;Reynolds and Wardle, 1993). Other climatic variables such solar radiation or water distribution are also important for the optimum development of color and aroma during ripening (Sebastian et al, 2015;Gregan et al, 2012), and also affect berry sizes and overall yield (Ubalde et al, 2010). However, within a specific climate zone, soil is the most important environmental factor controlling within vineyard vine development and fruit or wine quality (Sotés and Gómez-Miguel, 2003).…”

What is the expected impact of climate change on wine aroma compounds and their precursors in grape?

“…The work of Allen and Lacey (1993) and Falcao et al (2007) showed that IBMP levels in wines are lower when the temperature is higher during the growing season. This phenomenon is amplified by exposure of the grapes to light and the removal of the basal leaves that contain IBMP during the nouaison-grape closure stages of the vine (Ryona et al, 2008;Gregan et al, 2012.). Conversely, the IBMP content is higher in grapes from vigorous vines with a high vegetation density (Allen and Lacey, 1993).…”