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Embryo culture in vitro in the experimental evaluation of drought resistance in cereals (review)

Drought is an unfavorable combination of meteorological conditions when plants experience a long-term water deficiency both in the air and soil. This is one of the most common abiotic stressors, which leads not only to significant crop losses but also rises threat to food security. Researchers are actively developing ways to breed drought-tolerant cultivars of economically valuable crops, especially cereals – the main food resource. One of the promising areas of biotechnological evaluation of the resistance of existing and newly created cereal genotypes to drought for breeding purposes is the use of culture in vitro. In this case, embryos at the particular stage of development are used as explants (so-called embryo culture in vitro). The review aims to analyze the literature and own data on the production of cereal regenerants in embryo culture in vitro under selective experimental conditions of imitation of physiological drought. It has been shown that in vitro cultivation of immature embryos at a critical stage of relative autonomy is especially promising. This kind of embryo does not depend on the physiological factors of the maternal organism and can autonomously give rise to the fully developed plant under adequate conditions in vitro and later ex vitro. This allows the biotechnologist to obtain regenerants directly, excluding an additional time-consuming stage of the formation of morphogenic calli in vitro. As follows, the time required for expensive experiments is also reduced. Data on the identification of the critical stage of the relative autonomy of the cereal embryogenesis are presented. Criterion (proposed by the authors) for identifying this stage by the ability of the embryos to complete embryogenesis and form the seedlings on a hormone-free medium in vitro and give rise to the full developed regenerants ex vitro has been analyzed. Furthermore, the analysis of the laboratory germination of the obtained caryopses was carried out. It was discovered that in spring soft wheat, for example, such stage, corresponding to the formation of all organs in the embryo, occurs 15 days after pollination. The issues of using relatively autonomous embryos in the biotechnological assessment of the genotype drought resistance under selective conditions in vitro are considered.