Sunburn Damage Assessment Under Different Levels of Sun Exposure and Temperature in Sangiovese and Pignoletto Berries
Gianluca Allegro,* Chiara Pastore, Gabriele
Valentini, Riccardo Mazzoleni, and Ilaria Filippetti
*Department of Agricultural and Food Sciences – University of
Bologna, viale Fanin, 46, Bologna – 40127, Italy
(gianluca.allegro2@unibo.it)
In the low-vigor vineyards of the North Italian hills, sunburn damage has drastically increased due to elevated summer temperatures and prolonged drought caused by climate change. With serious consequences on yield and berry composition, sunburn damage is now an emerging issue in these wine areas. In 2021, we conducted a study on the Vitis vinifera cultivars Sangiovese (red) and Pignoletto (white) to determine the role of cluster exposure and berry temperature on sunburn symptoms. Three levels of cluster exposure were imposed at veraison by leaf removal to differentiate the light incidence on the berries and their temperature. Afterward, the evolution of sunburn browning, sunburn necrosis, and berry shrivel was monitored weekly. Berry temperature was recorded continuously by thermocouples to identify the threshold level for the appearance of each symptom. A thermocamera was used to monitor changes in cluster temperature during the day. Damaged berries were sampled throughout ripening and high-performance liquid chromatography analysis was used to characterize sunburn browning and berry shrivel in terms of anthocyanin and flavonol content. Sunburn necrosis was observed on the most exposed berries of both varieties just after leaf removal and this damage worsened with maximum berry temperatures > 40°C. Berry shrivel appeared on Sangiovese only about three weeks after veraison and progressed until harvest, often leading to complete dehydration of the berries. Broadly, berry shrivel reduced concentrations of anthocyanins and flavonols (expressed as mg/berry) compared to healthy berries. Sunburn browning was evident only on Pignoletto, in berries receiving the most sunlight, and the concentration of flavonols increased with intensification of the brown color. In the next seasons, adaptation strategies will be tested on both varieties.
Funding Support: This project is part of the ERA-NET Cofund ICT-AGRI-FOOD, with funding provided by national sources (Italian Ministry of University and Research) and co-funding by the European Union’s Horizon 2020 research and innovation program, Grant Agreement number 862665.
