The dissertation is focused on the study of the physiological bases of the formation of the quality grain of 24 genotypes of spring wheat (Triticum aestivum L., T. durum Desf., T. turgidum subsp. dicoccum) of Ukrainian selection, with an emphasis on the content of Fe, Zn, Cu and the identification of wheat endophyte bacteria and the study of their relationship with grain yield and quality. Wheat is one of the most cultivated crops in Ukraine and the world. In the coming years, it is necessary to improve the quality of wheat grain and its production in sufficient quantity for the population, which will increase by 36 % by 2100. “Hidden hunger” caused by a lack of vitamins and microelements is an urgent problem of nutrition and health for 2 billion people worldwide. It is the most common form of malnutrition. The study of complex physiological mechanisms of absorption and maintenance of the necessary concentration of trace elements in plant tissues, the search and research of wheat varieties with the increased ability to accumulate them in the grain is an essential prerequisite for the development of effective methods of biofortification, environmentally safe technologies that would complement the phenotypic plasticity and adaptability of plants. Bacterial endophytes can serve as tools for developing new strategies for biofortification and food security. An analysis of the main physicochemical properties of the soils of two experimental plots with different bioavailability of microelements: Dmytriv area (50°13'26.6"N 24°36'50.5" E) and D. Luzhok (49°27'17.5"N 23°23'02.6" E). The drought tolerance of the studied wheat varieties was taken in the field experiment. Differences in response to drought among soft and hard wheat varieties were confirmed. The average yield of wheat in 2017 on the Dmytriv plot was 67 % higher than on the D. Luzhok plot. In 2018, a 53 % higher grain yield was obtained at the Dmytriv site. In addition, higher grain yields were established for soft wheat varieties. The total protein content in wheat grain ranged from 8.65 to 17.21 %. The higher content of proteins in grain was observed on the D. Luzhok plot. Varieties with an increased ability to accumulate proteins in grain under different conditions of mineral nutrition: Etiud, Kolektyvna 3, Dynastiia, Izol’da, and Holikovs’ka. As a result of the analysis of the yield and structure of the crop, it was assumed that the varieties Dubravka, Oksamyt myronivs’kyi, Chado, Dynastiia, are more resistant to environmental factors, with their inherent higher adaptive plasticity to conditions cultivation, under the conditions of a different provision of mineral elements. The dependence of the concentration of Fe, Zn, and Cu in wheat organs on the content of their available forms in the soil was confirmed. The ability of varieties to accumulate Fe, Zn, and Cu in flag leaves and spikes with their subsequent loading into grain was investigated. Correlations between concentrations of microelements were established. It was found that the higher yield is characteristic of the varieties under the conditions of cultivation on chernozems of carbonate rocks with a high content of soil organic matter and low bioavailability of Fe, Cu, and Zn. Bacterial endophytes of grain and vegetative organs of spring wheat seedlings obtained in vitro were identified for the first time in the work. Their ability to accumulate Fe, Zn, and Cu differed due to their low bioavailability. From spring wheat grain, 20 endophytic bacteria strains were isolated, cultivated, and identified, representing the genera Staphylococcus, Pantoea, Sphingobium, Bacillus, Kosakonia, Micrococcus, Kocuria, and Corynebacterium. The determined nucleotide sequences of bacterial endophytes are included in the GenBank database under the names MT302194 – MT302204, MT312840, and ОР445710 – ОР445717. Cultivated strains demonstrated the ability to synthesize and secrete auxin-like compounds into the culture medium (IRCs max.: 16.57 µg·mL−1). As a result of the metagenomic analysis of the tissues of roots and leaves of wheat seedlings obtained in sterile in vitro culture, 14 genera of bacteria were identified. It has been proven that sterile embryos became the starting point of formation of the endophytic microbiome of wheat seedlings grown in sterile conditions in vitro. Bacterial endophytes of grain and tissues of leaves and roots of T. turgidum subsp. dicoccum was isolated and identified for the first time. The presented results provide novel insights into the relationships between the grainendophytic bacteria, the Fe, Cu, and Zn concentrations, and the yield in the spring wheat varieties grown with limited bio-availability of these microelements in the field. A detailed analysis of the composition and functions of the endophytic microbiome of spring wheat can contribute to developing a new group of biological preparations – phytoprobiotics.
