Pavlyshche A. Formation and functioning of soybean‒Bradyrhizobium japonicum symbiosis under using physiologically active substances with fungicidal activity

The dissertation is devoted to the study of physiological and biochemical peculiarities of formation and functioning of legume‒rhizobial symbiosis under the conditions of seed treatment, and improvement of ways of increasing the productivity of soybean plants with the use of nitrogen-fixing bacteria and fungicides. It is established that the investigated fungicides do not exert a bactericidal effect on Bradyrhizobium japonicum 634b nodule bacteria in laboratory conditions, however, they influence the process of formation of root nodules, significantly inhibit the activity of nitrogen fixation, the photosynthetic and transpiration rate at the initial stages of plant development, but subsequently the effect of the disinfectants is eliminated. Complex influence of fungicidal preparations on macro- and microsymbionts was noted. The changes of the activity of antioxidant enzymes ‒ superoxide dismutase, ascorbate and guaiacol peroxidase in soybean plants and the content of organic acids in its roots, were estimated that allowed us to confirm the development of stress-protective reactions of the plant to the treatment and the ability to adapt to the effects of stressors, ensuring the effective functioning of symbiotic systems. It is shown that the process of formation and functioning of symbiotic systems of soybean‒B. japonicum and grain productivity of plants depend significantly on the active ingredient of the fungicide, method, treatment time and conditions of cultivation, and the softening of the inhibitory effect of fungicides can be achieved by early treatment and treatment by vegetation. The results obtained can be the basis for improving existing and developing new elements of soybean cultivation technology and ensuring the effective formation and functioning of legume and rhizobial symbiosis while protecting plants from phytopathogenic hazards.