S16 - Session O3 - Irrigation during ripening may reduce sunburn damages on berries of cv. Sangiovese (Vitis vinifera L.)

Authors: Gianluca Allegro *, Chiara Pastore, Gabriele Valentini, Riccardo Mazzoleni, Ilaria Filippetti

In the Mediterranean wine-growing areas, heat waves that occur more frequently due to climate change, may cause severe sunburn damages on clusters with serious consequences on yield. Therefore, high temperatures often hasten sugar accumulation causing the decoupling between technological and phenolic maturity. Considering these issues, the approach on vineyard management has recently been reconsidered and also irrigation may be applied in an innovative way. The aim of the present study was to investigate the effects of irrigation during berry ripening on berry sunburn symptoms and on yield and grape composition at harvest. The trial was conducted in 2021 on adult vines of cv. Sangiovese ( Vitis vinifera L.), trained to VSP spur-pruned cordon. Treatments were laid out in a strip-plot design and the main factors were irrigation and cluster exposure. Irrigation treatments were: a) irrigation from the beginning of veraison to harvest to maintain vines well-watered; b) no irrigation. Cluster exposure treatments were: c) removal of main and lateral leaves from the eight basal nodes of each shoot at the beginning of veraison; d) no leaf removal. From veraison to harvest, berry temperature was continuously measured with thermocouples inserted under berry skin, while the intensity and severity of sunburn damages were recorded weekly as well as the midday stem water potential. At harvest, yield parameters were measured and grape composition analysed, while frozen berries were used for anthocyanin analysis with HPLC. As expected, leaf removal caused berry necrosis and berry shrivel due to the increase of berry temperature, but irrigation halved the severity of those sunburn damages. Sugar and anthocyanin concentration were slightly affected by leaf removal but decreased significantly with irrigation. This study showed an interesting approach to tackle sunburn damages and to slow down sugar accumulation, that still needs to be modulated to avoid detrimental effects on anthocyanin accumulation.