Content of biologically active substances in strawberry (Fragaria × Ananassa) grown in the Forest-Steppe of Ukraine

Aim. To investigate the impact of weather conditions in the Forest-Steppe of Ukraine and genetic specificities of cultivars on the content of vitamin C, polyphenols, flavonoids, and anthocyanins in strawberry fruits. Methods. The study was conducted in 2023–2025; strawberry fruits of 7 cultivars of different ripening periods were selected in the experimental plots of the Institute of Horticulture of the NAAS of Ukraine. The weather indices of the vegetation period prior to collecting strawberry fruits were taken from the meteorological station Vantage Pro2 Plus, located in the experimental plots of the strawberry. The analytical study was conducted by the method of determining the quality of fruit and berry products (Kondratenko et al., 2008), in particular, using spectrophotometry methods, the content of biologically active substances was determined and expressed in mg/100 g FW. The amount of vitamin C was determined using titration with the solution of 2,6-dichlorophenolindophenol, the content of polyphenolic substances was determined using the Folin-Denis reagent, the content of flavonoids by measuring the absorption of the complex of flavonoids by aluminum chloride in the ethanol medium, the content of anthocyanins by the difference method in two buffer systems: with potassium chloride, pH 1.0 (0.025 M) and sodium acetate, pH 4.5 (0.4 M). The statistical analysis of the study data was conducted in STATISTICA 13/1 (StatSoft, Inc., USA). Results. The weather indices of the period of growth and development of strawberry fruits had a considerable impact on the content of vitamin C, polyphenols, flavonoids, and anthocyanins in them. The content of vitamin C in the fruits of cultivar Herkules was the most stable and independent from weather conditions of the cultivation year, with a minimum of 50.4, a maximum of 57.6, and an average of 53.5 mg/100 g FW. The content of vitamin C in strawberry cultivars Florence and Vibrant was the most variable and dependent on the weather conditions of the cultivation year, the average content was 52.0 and 50.9 mg/100 g FW. The amount of vitamin C in strawberry fruits considerably depended on the average daily air temperatures; the correlation coefficients for the investigated group of cultivars were high, over 0.720, the increase in the average daily air temperatures promoted a decrease in the content of vitamin C. The amount of polyphenols in cultivars Herkules and Prezent had a significant correlation with the average daily air temperatures and the HTI for the period of their growth and development, but in the first case, the correlation was direct, and in the second one, indirect. Among the investigated cultivars, the fruits of cultivars Veselka, Vibrant, and Florence were capable of accumulating the maximal amount of flavonoids, over 70 mg/100 g FW. The fruits of Prezent cultivar were capable of accumulating more than 20 mg/100 g FW of anthocyanins. The content of flavonoids in Prezent cultivar and that of anthocyanins in Veselka cultivar was homeostatic. Conclusions. It was determined that the content of biologically active substances in strawberry fruits was determined by genetic specificities of the cultivar and corrected by weather conditions for the period of their growth and development.