Physiological and biochemical evaluation of resistance to heat and drought in apple varieties

Abstract

The results of physiological and biochemical evaluation of resistance to heat and drought of five apple tree varieties of different ecological and geographical origin in the conditions of the Krasnodar Territory are presented. The following varieties were studied during 2020-–2022: Interprise (America), Florina (France), Orphey, Margo, Bagryanets Kubani (Russia). Indicators of water regime were determined by the weight method after drying the samples in the thermostat at 105°C to constant weight. The content of photosynthetic pigments was determined spectrophotometrically in 85% acetone extract. The ascorbic acid content was determined by capillary electrophoresis. Under the conditions of tension stress factors of the summer period, the varieties Orphey and Margo showed the smallest decrease in water content of the leaf tissues (by 1.32–1.45%) in comparison with the other studied varieties (by 2.40–3.27%). Orphey and Margo varieties showed the highest values of bound water to free water ratio in all summer months, which in August were 9.95 and 9.97, respectively, in other varieties they were 6.54–7.46. Stable content of the sum of chlorophylls during the summer in the varieties Orphey and Margo, as well as low ratios of the sum of chlorophylls to carotenoids, amounting to 2.65 and 2.74 in August, respectively, in comparison with the other studied varieties (3.15–3.46) indicate increased adaptability of their leaf tissues. In response to drought, Orphey and Margo varieties showed an increase in ascorbic acid content to a greater extent (2.02–2.58 times) compared to the other varieties studied (1.17–1.59 times). Orphey and Margo varieties have shown themselves to be more adaptable for cultivation in the conditions of the Krasnodar Territory. They can be used in breeding to develop the most heat- and drought-resistant varieties.