PHYSIOLOGICAL METHODS TO EVALUATE THE ADAPTIVE POTENCIAL OF PEAR CULTIVARS

Weather conditions in the southern regions are more and more often characterized by an increase in temperature indicators and a decrease in relative humidity during the summer. Such changes lead to an increase in the negative impact on cultivated plants with high-temperature stress and drought, which can be reflected in low yields. The ability to adapt to environmental conditions is not the same for different genotypes, so, there is a problem of assessing the most effective ways to protect and maintain plant growth and development processes. Using the example of a pear, which is a perennial fruit crop and, accordingly, undergoes annual effects of abiotic stress factors, the physiological features of five cultivars were studied during the hottest and driest summer period. The content of soluble sugars, phenolic compounds, and the activity of enzymes such as polyphenol oxidase, superoxide dismutase, and peroxidase were determined in plant leaves. It was found that with the increasing negative impact of weather conditions, in 2023 pear cultivars ‘Conference’, ‘Williams’, ‘Krasnodarskaya zimnaya’ and ‘Flamenco’ had a phenolic compound content 1.2–2 times higher than in 2022. Changes in the accumulation of soluble sugars were not significantly significant. The dynamics of the activity of polyphenol oxidase and peroxidase was correlated with the content of phenols and increased in the summer of 2023 by 1.5–3.7 times in most cultivars. The level of superoxide dismutase activity, on the contrary, reached its maximum values in the milder summer period of 2022, with the exception of the ‘Conference’ cultivar, which showed a 28 % increase in activity in 2023. Thus, it can be concluded that the accumulation of phenolic compounds and changes in the antioxidant enzymes activity in the leaves of different pear cultivars are marker indicators of the response to abiotic stress factors during the summer period.