Physio-biochemical criteria for apple tree tolerance to summer abiotic stresses

In Russia's North Caucasus where drought is frequent the apple tree is one of the most important garden crops. Physiological and biochemical studies are necessary to assess adaptiveness of apple varieties to stressors during summer, in particular, to summer drought. The purpose of this work is to study physiological, biochemical and anatomical parameters of leaves to assess the water regime, photosynthetic activity of apple trees in summer conditions, and to identify the most drought tolerant varieties for cultivation in the North Caucasus region. Research was carried out in 2011-2013 in fruit-bearing plantations (Central'noe Farm, Krasnodar) on apple varieties of different eco- geographical origin and ploidy: Idared, Earle Mack, Dayton (United States), Ligol (Poland), Prikubanskoe, Rassvet, Fortuna, Soyuz, Rodnichok (Russia). Varieties Soyuz and Rodnichok are triploids, the rest ones are diploids. Monthly, fully formed leaves were collected from (from the middle part of annual shoots of three trees in 3 replicates for each variety, 10 leaves per replicate...