Stolbikova A. V., Shishparenok A. A., Rudikovskiy A. V., Rudikovskaya E. G., Dudareva L. V. Possible Involvement of Gibberellins in the Formation of Dwarf Varieties of Siberian Crab Apple Malus baccata (L.) Borkh. in the Conditions of Forest-Steppe

In the transition zone between the forest and the steppe (in the ecotone) in the territory of the Buryatia Republic, dwarf species (up to 110 cm in height) of Siberian crabapple Malus baccata (L.) Borkh. were found that differ from other (up to 250 cm in height) apple trees. To determine the causes of brachysm by physiological methods, the influence of gibberellins on growth processes were studied. After exogenous application GA3 to the shoot apex of the dwarf apple, we observed a significant increase in growth processes in the apical part of the shoots as compared to the shoots without application. The sensitivity to this hormone, which is found in the dwarf trees, allows to assume the absence of mutations in the genes of repressor proteins of the gibberellin signal and initiates the dilatation of intercalary meristems. The phytohormonal extracts of apple-tree leaves did not remove short stature in dwarf mutants of peas in any of the experiment variants, which may indicate the possible presence in the apple leaves of endogenous retardants. The previously established lower content of indolyl-3-acetic acid in dwarf, compared to tall trees, and the associated differences in IAA / ABC indices, as well as the revealed gibberellin dependence of a dwarf apple, may indicate the participation of phytohormones in the formation of dwarf status M. baccata, as an adaptation to the stressful conditions of growth, especially to insufficient moisture, in the forest-steppe ecotone of the Selenga Dauria.