Nitrogen deficiency is a limiting factor in increasing efficiency of crop production in terrestrial ecosystems, and the transformation of inert nitrogen to forms that can be assimilated by plants is mediated by soil microorganisms. Symbiotic nitrogen-fixing bacteria and roots depend on each other and have developed various mechanisms for symbiotic coexistence. The aim of this work was to investigate the role of nitrogen deficiency on growth and development near isogenic by E genes lines of soybean (Glycine max (L.) Merr.): short-day (SD) line with genotype Е1е2е3(Е4е5Е7), and photoperiodic insensitive (PPI) line with genotype е1е2е3(Е4е5Е7) grown from seeds inoculated with active strains of Bradyrhizobium japonicum against the background of local populations of diazotrophs of the genus Azotobacter spp. and establish how the soybean – Bradyrhizobium symbiosis will develop as the genes of both microsymbionts and macrosymbionts are responsible for the formation of the symbiotic complex. Plants were grown in a vegetation chamber, in sand culture. To assess the quantitative composition of microorganisms in the rhizosphere and rhizoplanes, 6 plants were selected from each soybean line, then separation of the zones of the rhizosphere and rhizoplanes was performed using the method of washing and the resulting suspension was used for inoculation on dense nutrient media (mannitol-yeast agar medium and Ashby medium). The results of study showed that seed inoculation and co-inoculation provides faster formation of the symbiotic soybean – Bradyrhizobium complex. Differences in nodulation rates between the short-day line with genotype Е1е2е3(Е4е5Е7), and a photoperiodic insensitive line with genotype е1е2е3(Е4е5Е7) were identified. Determination of the amount of B. japonicum on the medium of mannitol-yeast agar in the rhizosphere and rhizoplane showed that inoculation by B. japonicum strain 634b caused a significant increase in the amount B. japonicum in the rhizosphere and rhizoplane in both soybean lines, comparison with non-inoculated seeds. Then, co-inoculation by B. japonicum strain 634b + Azotobacter chroococcum significantly increased the amount of B. japonicum only in the rhizoplane and decreased their number in the rhizosphere. Determination of the amount of A. chroococcum on the Ashby elective medium in the rhizosphere and rhizoplane showed that the inoculation by B. japonicum strain 634b caused a significant decrease in the amount of A. chroococcum both in the rhizosphere and in the rhizoplane of the PPI line of soybean, and in the rhizosphere the SD line, in comparison with non-inoculated seeds. That can testify to the competitive interaction of these microorganisms. However, the co-inoculation by B. japonicum strain 634b + A. chroococcum in the SD line significantly increased the number of A. chroococcum in the rhizoplane and decreased their number in the rhizosphere, in the PPI line their number decreased in the rhizoplane and increased in the rhizosphere, in comparison with non-inoculated seeds. Probably, the E genes (their dominant or recessive state) of soybean isogenic lines affect the regulation of the content and distribution of sugars. It was established that the nitrogen deficiency stimulated development of the root system of plants and the synthesized sugars were distributed predominantly to the root system growth. We suppose that the seeds’ inoculation had extended sugar consumption to the symbiont, due to which it compensates the lack of nitrogen, but leads to a slower growth of the root system.

Soybean (Glycine max (L.) Merr.) is a typical short-day and thermophilic crop. Absence of or low sensitivity to photoperiod is necessary for short-day crops to adapt to high latitudes. Photoperiod insensitivity in soybeans is controlled by two genetic systems and involves three important maturity genes: E1, a repressor for two soybean orthologs of Arabidopsis FLOWERING LOCUS T, and E3 and E4, which are phytochrome A genes. The aim of this work was to investigate the role of four maturity genes (E1 through E4) on the yield components, seed quality and on phasic development of near isogenic by E genes lines of soybean: short-day (SD) lines with genotype e1E2E3E4e5E7, e1E2E3e4e5E7, E1e2e3E4e5E7 and photoperiodic insensitive (PPI) lines with genotype e1e2E3E4e5E7, e1e2e3E4e5E7 under a long photoperiod (the natural day length of 50 latitude) conditions and short day conditions. The results of the study showed that soybean development processes under conditions of different day lengths depend on the dominant/recessive state of the main maturity genes. In addition, the response to the photoperiod depends on certain combinations of genes. SD lines began flowering on average 16.9% later under the conditions of a natural long photoperiod. Dominant alleles of genes E1 and E3 extended the pre- and post-flowering phases under conditions of exposure to long and short photoperiods. The dominant allele of the E1 gene delayed the onset of flowering by an average of 26.9%, and the period of full maturity by 39.8% compared to the recessive e1. The dominant allele of the E3 gene, compared to the recessive e3, lengthened the transition to flowering by an average of 16.1%, and the period of full ripeness by 27.1%. The dominant allele of the E2 gene lengthened the duration of the vegetative phase by 20% under the conditions of a long photoperiod. No significant influence of the dominant E4 allele on the duration of the vegetative and generative phases of soybean development was found in our study. PPI lines begin flowering under the conditions of a long and short photoperiod at the same time, but the phases of flowering and full seed maturity in the line with genotype e1e2e3E4e5E7 occurred earlier, due to the loss of the photoperiod sensitivity of the E3 gene. PPI line with genotype e1e2e3E4e5E7 proved to be the most insensitive line to the effect of different photoperiod durations among the studied lines. It was shown that the dominant alleles of E1–E4 maturity genes reduced the parameters of seed weight per plant and the weight of 1000 seeds under the conditions of a natural long photoperiod in comparison with recessive alleles of these genes. The maximum weight of seeds per plant and the weight of 1000 seeds were recorded in the PPI line with genotype e1e2e3E4e5E7. It should be noted that the dominant alleles E1 and E3 increased yield under conditions of a short photoperiod. Maturity genes had different effects on the biochemical composition of seeds. It was shown that soybean lines with dominant E1, E2 and E4 genes showed a higher content of starch and a lower content of total nitrogen and oil in seeds under natural photoperiod conditions compared to lines with recessive alleles of these genes. The dominant E3 allele reduced the oil content and did not affect the starch and total nitrogen content of seeds under long day conditions compared to the recessive e3 allele. The analysis of the effect of photoperiod on the timing of phenophases, yield structure indicators and biochemical composition of seeds in soybean plants with different sensitivity to photoperiod showed that the PPI line with the genotype e1e2e3E4e5E7 was the most adapted to the natural conditions of 50 degrees latitude. The PPI line with the genotype e1e2e3E4e5E7 was characterized by the shortest phases of days from sowing to flowering and full maturity. As a result, this line had the shortest growing season without reducing the yield and seed quality. Clearly, photoperiod had strong effects on all stages of plant reproduction and often acted indirectly, as shown by delayed responses expressed in later phases of development. The obtained results can be useful for the selection of soybean cultivars adapted to the climatic conditions of cultivation of Kharkiv region.