Seasonal dynamics of sugar content and acidity in berries of the don native grape variety Varyushkin

The purpose of the study is to analyze the patterns of long-term and seasonal dynamics of the content of sugars and titratable acids in grapes using the example of the Don aboriginal variety Varyushkin. The study was carried out on the Don ampelographic collection named after Ya.I. Potapenko (Novocherkassk, Rostov Region) in 2006-2021. The sugar content and titratable acidity of the berries were determined; analyzes were made 2-4 times per season. The study was carried out using methods generally accepted in viticulture and GOSTs. Trends and agro-climatic dependencies were assessed by methods of correlation and regression analysis. In recent decades, in the Lower Don Region, there has been an increase in temperatures, a decrease in precipitation and a hydrothermal coefficient (HTC). On average, over 16 years of study during the period of technological maturity, the sugar content of berries in the Varyushkin variety was 22.0 g/100 cm3 (variation coefficient 6.6 %), titratable acidity - 7.7 g/dm3 (variation coefficient 15.3 %). Conditions of grapes at the stage of technical maturity did not have significant trends. The main agro-climatic factor of conditions turned out to be HTC for the period with temperatures above 5 °C (HTC5), with a decrease in HTC5 per unit, sugar content increased by 4.5 g/100 cm3, and acidity decreased by 3.7 g/dm3. An analysis of seasonal dynamics revealed that, on average, the growth rate of sugar content was 0.080 g/100 cm3/day, and the rate of acidity decrease was 0.043 g/dm3/day. The growth rate of sugar content increased in years with a shorter period from the beginning of ripening to full maturity of the berries. Climate change is still neutral for grape conditions.