TACTICS OF EXPLANT CHOICE IN BIOTECHNOLOGICAL STUDIES OF WHEAT DROUGHT RESISTANCE BY EMBRYO CULTURE <i>IN VITRO</i> METHOD FOR BREEDING PURPOSES
Drought is assessed as an unfavorable combination of meteorological conditions in which plants experience a long-term water shortage in the air and soil. One of the directions of experimental evaluation of plant drought resistance in vitro is to use embryos at one or another stage of development as explants (embryo culture in vitro ). The prospects of this direction are determined mainly by the fact that the embryo has all the morphogenetic potentials of an adult organism (Батыгина, 2014), including the ability to withstand various stresses. In biotechnological studies using in vitro embryoculture, depending on the goals of a specific breeding program, it is important to carry out the right tactics for choosing an embryo as an explant at a certain stage of embryogenesis. It is the chosen stage of explant embryogenesis that determines which method the process of regenerant formation in vitro will follow: indirect (according to the scheme "one embryo → one callus → several regenerants") or direct (according to the scheme "one embryo → one regenerant"). Using the example of spring soft wheat, the article presents an overview of a number of literature and original data on the direction of biotechnological studies of drought resistance using the embryo culture in vitro method. The main attention is paid to the analysis of the structural features of wheat embryos at the early and middle stages of organogenesis associated with the induction of indirect and direct methods of formation of regenerants in embryo culture in vitro .