Berry shattering phenomena in vineyards: The influence of maximum temperatures during flowering period in an extreme year

Phenological stages, vine yield, and quality of grapes are increasingly affected by extreme temperature conditions caused by climate change. This study aimed to investigate the impact of high temperatures over 40 °C at the flowering period of cv. Sultana Seedless (Vitis vinifera L.) vineyards on the berry shattering problem. A total of 79 vineyards were examined in the western region of Türkiye, and a level of berry shattering (0–4) was defined rapidly to determine the extent of the damage caused by high temperatures. When the two years were compared, it was found that the flowering period was eight days shorter in the first year due to the high temperatures. The study found that the berry shattering problem was more severe in the first year than in the following year among vineyards in Saruhanli, Yunusemre, and Ahmetli locations. High temperatures during the flowering period in the 2020 growing season had a more significant impact on vine yield, resulting in more berry-shattering problems compared to the second year. However, the overall number and weight of clusters increased by between 15.15%-39.52% and 20.51%-42.49% in all locations respectively, under seasonal norms in the following year. Two-year analyzes made in the same vineyards revealed that high temperatures during the flowering period are more effective than the subsequent year, affect the yield of the vines, and more berry shattering problems occur. This study also recommended that the maximum temperatures be examined during specific days and hours during the flowering period, as well as the duration of exposure. Temperatures above seasonal norms can decrease yield and cause berry shattering.