Relation of soybean productivity to the functioning of the symbiotic and photosynthetic apparatuses

Background. Increasing the yield of soybean necessitates the maintenance of a high protein level in seeds, and therefore the process of fixing atmospheric N2. Seed inoculation with soybean nitrogen-fixing bacteria is known to improve N2-fixation and soybean grain yield. At the same time, the introduction of new nodule bacteria strains into preparations for soybean inoculation requires the study of their influence on the main interconnected physiological processes that form the basis of leguminous plants productivity – N2-fixation and photosynthesis. The aim of the work was to study the relationship of vegetative growth and grain productivity of soybean inoculated with new nodule bacteria Bradyrhizobium japonicum strains of different functional activity with the plants’ symbiotic and photosynthetic apparatuses functioning. Materials and Methods. The research was carried out on symbiotic systems created with soybean plants (Glycine max (L.) Merr.) of the Almaz variety and nodule bacteria B. japonicum strains: analytically selected PC09, and recombinant strains B157, B201, D45, D52 (pSUP5011::Tn5mob) and C30 (pSUP2021::Tn5) from the N2-fixing microorganisms museum collection of the Institute of Plant Physiology and Genetics NAS of Ukraine. Research methods – microbiological, biochemical and physiological, statistical analysis. Results. It was found that the N2-fixing activity (NFA) of nodules formed by B. japoni­cum PC09, D45, D52, B157 and B201 strains at the stage of 3 true leaves exceeded the NFA of nodules formed by Tn5-mutant C30 by 1.6–4.0 times, and at the stage of budding–beginning of flowering – by 4.2–6.2 times. Highly active strains also differed from each other in NFA, although to a lesser extent than with strain C30. On the basis of a comparative analysis of the physiological indices of soybean inoculated with B. japonicum strains of different activity, close positive linear correlations were found between NFA, photosynthetic rate, and the biological and grain productivity of plants. Conclusions. The results obtained indicate that the higher the nodulating and NFA of rhizobia in the symbiotic system soybean–Bradyrhizobium japonicum, the higher the functional activity of photosynthetic apparatus formed by plants. This provides a more complete genetic potential release of soybean crop productivity.