Use of physiological and biochemical indicators to identify apple varieties resistant to drought

As a result of global climate change in the arid regions of the world, a decrease in the adaptability of fruit crops to drought has been noted. This explains the interest of researchers in the issues of increasing the drought resistance of fruit crops in various ways, one of which is the creation of resistant varieties as a result of selection. The use of physiological and biochemical parameters in the breeding process as diagnostic criteria for drought resistance and the identification of highly adaptive varieties of fruit crops is relevant all over the world. The objects of study are apple varieties of various ecological and geographical origins: Idared, Erli Mac, Dayton (USA), Prikubanskoe, Rassvet, Fortuna (Russia). Physiological parameters: the relative water content, the total content of chlorophylls (a + b), carotenoids, ascorbic acid in the leaves of the studied apple varieties were determined during periods before drought and during drought. Differences in the response of varieties to the impact of drought were revealed. It was found that apple varieties of local selection Prikubanskoye, Fortuna and American variety Idared have a greater ability to adapt to changing environmental conditions in comparison with other studied varieties. The revealed adaptive features during drought (retention of a high relative water content, stability of the pigment system, a low ratio of the total chlorophyll to carotenoids, an increased content of ascorbic acid) make it possible to use them in breeding as donors of drought resistance traits. The data of physiological and biochemical studies, obtained in the unique natural and climatic conditions of the North Caucasus region of Russia, complement fundamental research on the physiological foundations of apple tree adaptation to drought