Abstract

--- - Background and goals - Sunburn is one of the most important problems in fresh fruit production, but little information exists about its effect on the winegrape industry. The objective of this study was to physically and chemically characterize the severity of sunburn in berries from traditionally farmed Muscat of Alexandria vineyards. - Methods and key findings - Three Muscat of Alexandria nonirrigated vineyards, each of a high (similar to 50 cm from the soil) and a low (2 to 10 cm from the soil) fruit zone height, were selected in the Itata valley, Chile. Sunburn damage at commercial harvest was estimated for two consecutive years. There were no differences in soluble solids concentration, weight, shape, color, or sunburn severity of berries between fruit zone heights. Results showed that 40% of sampled berries exhibited moderate to severe symptoms of sunburn. The appearance of sunburn lesions on the berry surface correlated with changes in hue and maximum chlorophyll fluorescence, but not with the concentration of soluble solids. In general, greater concentrations of volatile terpenes were associated with more severe symptoms of sunburn in berries, and linalool showed the clearest response to sunburn damage. - Conclusions and significance - Contrary to previous research, our results indicate that moderate levels of berry sunburn induce positive changes in the aromatic profile of berries. However, the high incidence of berry sunburn found in the present study highlights the significant vulnerability of traditional farming systems to high solar radiation and thermal stress.