Sunburn in Grapes: A Review

Abstract

Sunburn is a physiological disorder that affects the visual and organoleptic properties of grapes. The appearance of brown and necrotic spots severely affects the commercial value of the fruit, and in extreme cases, significantly decreases yield. Depending on the severity of the damage and the driving factors, sunburn on grapes can be classified as sunburn browning (SB) or as sunburn necrosis (SN). Sunburn results from a combination of excessive photosynthetically active radiation (PAR) and UV radiation and temperature that can be exacerbated by other stress factors such as water deficit. Fruit respond to these by activating antioxidant defense mechanisms, de novo synthesis of optical screening compounds and heat-shock proteins as well as through morphological adaptation. This review summarizes the current knowledge on sunburn in grapes and compares it with relevant literature on other fruits. It also discusses the different factors affecting the appearance and degree of sunburn, as well as the biochemical response of grapes to this phenomenon and different potential mitigation strategies. This review proposes further directions for research into sunburn in grapes.

Development and Utilization of a Model System to Evaluate the Potential of Surface Coatings for Protecting Grapes from Volatile Phenols Implicated in Smoke Taint

“…For instance, fungal diseases such as powdery mildew, downy mildew and botrytis rot can be controlled by application of fungicides [ 20 , 21 ]. In more recent years, there has been an increase in the application of sunscreen protectants for the protection of crops against extreme heat [ 22 ]. The application of chemical reflectants (i.e., kaolin, calcium carbonate) to fruit can reduce sunburn severity by reflecting UV and IR light [ 23 , 24 , 25 ].…”

Missing Links in Predicting Berry Sunburn in Future Vineyards

“…Berry sunburn in grapevines is a recurring disorder that can reduce berry quality and cause severe yield loss (Keller, 2015). Recently, Gambetta et al (2021) reviewed current knowledge on berry sunburn in grapevine. They conclude that processes resulting in sunburn are highly complex and not fully understood, but key drivers of sunburn are local light conditions and heat impact on the berry surface and a cultivar-specific susceptibility of the berry to sunburn.…”

“…An increased emergence of sunburn has been observed in recent years in some vine regions in France and Germany (Gambetta et al, 2021). Given that berry sunburn is driven by extreme heat, more frequent and intense heatwaves, which can be expected in future (Masson-Delmotte et al, 2021), could indicate a link of climate change and sunburn.…”

“…Given that berry sunburn is driven by extreme heat, more frequent and intense heatwaves, which can be expected in future (Masson-Delmotte et al, 2021), could indicate a link of climate change and sunburn. Thus, a more frequent occurrence of sunburn could be expected in the future (Silvestre et al, 2019;Santos et al, 2020;Gambetta et al, 2021), but only if viticulturist could not fully adapt canopy management and associated practices.…”

“…While timing, extent, and need for leaf removal depend on local environmental factors, opening up the canopy at some point is usually recommended for promoting wine quality (Frioni et al, 2017;Hickey and Wolf, 2019;Satisha and Somkuwar, 2019;Würz et al, 2020;O'Brien et al, 2021). Even though, early leaf removal in the bunch zone can allow berries to better adapt to sunlight and, thereby, reduce their susceptibility to sunburn (Gambetta et al, 2021), leaf removal events just before or during a heatwave might dramatically increase sunburn occurrence due to newly sun-exposed berries being insufficiently adapted to the risky environment (Hayman et al, 2012;Palliotti et al, 2014). Again, if we expect more heatwaves due to climate change, this would shorten and reduce the time windows of leaf removal for protection against sunburn.…”