Comprehensive assessment of drought tolerance in clonal rootstocks of Malus Mill. bred at the Botanical Garden of Orenburg State University named after V.A. Bondarenko

Abstract

Climate aridification, the rate of which is accelerating year by year, has a significant impact on agricultural production, including fruit growing. Breeding drought-resistant cultivars is becoming a priority for breeders to ensure adequate crop yields. The apple tree is a vegetatively propagated fruit crop of global importance, and its fruits have high nutritional value. The preservation of important cultivar traits during propagation directly depends on the quality of the rootstock material used. Therefore, the aim of this study is to assess the drought tolerance of clonal rootstocks of Malus Mill. and to identify the forms most resistant to moisture stress for use as rootstocks for apple cultivars in the steppe zone of the Orenburg region or in regions with similar climatic and geographical characteristics. The objectives of the study were to determine the main parameters of the water regime in plant samples: total water content, water-holding capacity, mobile moisture content, rate of water loss, and severity of water deficit. The plant material comprised twelve forms of Malus clonal rootstocks, ten of which were semi-dwarf and dwarf growth forms. The Ural 5 and Ural 1 rootstocks were used as controls in each group due to their successful cultivation in the steppe zone of the Orenburg region. Based on a comprehensive assessment of leaf water regime parameters, three forms with greater resistance to moisture stress were identified compared to the controls: OB 1-15 among the semi-dwarfs, and OB 2-4 and OB 2-15 among the dwarfs. These clonal Malus rootstocks bred at the Botanical Garden of Orenburg State University are highly drought-resistant and can be used as rootstocks to maintain apple productivity in regions with arid climates.