Impact of heat and drought stress on Vranec grape quality in the Tikveš wine-growing region

Abstract

Although the grapevine (Vitis vinifera) is a thermophilic plant wich is well adapted to regions with warm and dry summers, it is increasingly affected by climate change. Rising average temperatures, more frequent drought periods, and extreme weather conditions lead to significant heat and water stress, which can negatively affect grape yield and quality.

The aim of this study was to evaluate the impact of extreme weather conditions during the 2024 growing season on the quality of grapes of the Vranec variety, the most widely cultivated red wine grape variety in the Republic of Macedonia. The research was conducted at eight locations in the Tikveš and Veles wine-growing regions using two experimental variants: irrigated and non-irrigated vineyards. At technological maturity, the mechanical composition of clusters and berries, the chemical composition of the must, and the chemical composition of the produced wine were analyzed. The results were compared with multi-year standard values for the Vranec variety.

The results show a significant influence of heat and water stress on the yield and quality of the Vranec variety. The average cluster weight decreased by 16.3% in the irrigated variant and by up to 48.1% in the non-irrigated variant, while the theoretical yield decreased by 6.4% and 14.8%, respectively. The must showed a pronounced imbalance in the chemical composition, characterized by high sugar content (up to 310 g/l) and low total acidity (4–5 g/l), accompanied by insufficient phenolic maturity of the seeds and the presence of ethanol, which indicates that the vines were exposed to considerable stress during the growing season.