Comparative evaluation of clonal apple rootstocks of various origin for use in the Irkutsk region

The use of clonal apple rootstocks represents a potential prospect for horticulture in the southern part of the Irkutsk region. This paper presents the results of long-term research in the Southern Cis-Baikal region. All studies were conducted in 2018–2024 at the collection sites of the Institute of Physiology and Biochemistry of the Siberian Branch of the Russian Academy of Sciences, located in Irkutsk and the Irkutsk district of the Irkutsk region. The study of rootstocks in the nursery plantation and variety-rootstock combinations in the garden was carried out according to the Program and methodology for variety study of fruit, berry and nut crops. As a result of the evaluation of clonal rootstocks, the Arm-18 and K-2 genotypes were assessed as slightly winter-hardy when cultivated in the conditions of the Irkutsk region in the period from 2018–2024, the remaining genotypes were assessed as winter-hardy. We classified the Siberian berry apple clone, Ural, Ural 2, 4-12 (Volga 12) and E-56 as highly winter-hardy clonal rootstocks. To evaluate the variety-rootstock combinations, several genotypes of clonal rootstocks were grafted with the varieties of winter-hardy semi-cultivated apple trees. All clonal rootstocks used for grafting, except for the control, the Siberian berry apple clone, were assessed as winter-hardy, the Siberian berry apple clone as highly winter-hardy. The semi-cultivated apple trees grafted onto clonal rootstocks began to bear fruit a year earlier than those grafted onto the Siberian berry apple tree, while no significant differences in the productivity of the trees studied were noted. Long-term studies have shown that most of the clonal rootstocks studied are promising for further study.