Abstract
Canopy shading is a widely used viticultural strategy for mitigating early grape berry ripening caused by global warming. In this study, we covered half of the canopy with a black shade cloth from the pea-size stage to harvest. In the fruit zone, canopy shade treatment (ST) reduced daily average solar radiation by about 74.6 % compared to the untreated control (UC), and significantly reduced daily average temperature. ST leaves were found to have lower net assimilation rates and higher internal CO2 concentration than in UC, which resulted in reduced yield, bunch weight, cane starch and berry total soluble solids. A delayed development stage was found in ST berries which had lower pH and higher titratable acid than UC. ST increased both berry and wine anthocyanin concentration while significantly decreasing flavonol concentration. ST wines had higher concentrations of a number of ester compounds and β-damascenone than UC wines, thus significantly enhancing the floral and fruity aroma of ST wines. Higher C6/C9 and fatty acids concentrations in ST berries may have caused higher ester concentrations in ST wines. The results showed significant effects on metabolites in berries and wines caused by canopy shade.
Highlights
Global warming has profoundly impacted many crops all over the world (Lobell et al, 2008)
The results show that only ΣCy and ΣDp content were significantly increased by shade treatment (ST) and there was no significant difference in other anthocyanin and total anthocyanin content between ST and untreated control (UC)
Grape and wine phenolic compounds were influenced by partial canopy shade significantly with an increase in anthocyanins and a decrease in flavonols
Summary
Global warming has profoundly impacted many crops all over the world (Lobell et al, 2008). The warmer climate has resulted in earlier vine phenological events with increased sugar at harvest. Unsynchronised sugar and phenolic compound accumulation makes it hard for winemakers to set a harvest date (Palliotti et al, 2014). Most winemakers delay the harvest date to ensure phenolic maturity and to avoid a herbaceous aroma, which results in higher alcohol levels and pH in the wines. To reduce the alcohol content of wines, wineries around the world have tried strategies such as membrane technology, supercritical extraction, or vacuum distillation. These technologies are relatively costly (Palliotti et al, 2014)
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