In the dissertation the ecological and biological properties of Bradyrhizobium japonicum isolates isolated from the сhernozem soils of Ukraine after their long existence in a saprotrophic conditions have been researched. Based on the conducted studies, the ecological and biological features of Bradyrhizobium japonicum isolates from the chernozem soils of Ukraine were identified, which ensure the formation and effective functioning of the symbiotic interaction with soybean plants under pre-treatment bacterization of seeds. The evaluation of the properties of Bradyrhizobium japonicum isolates from the soil, which ensuring the effective formation and functioning of symbiotic systems with Glycine max (L.) Merrill was evaluated. The formation of sustainable legume-rhizobial symbiosis is ensured by their nodulating ability, nitrogenase activity, the synthesis of exopolysaccharides, the effectiveness of interaction with soybean plants.
It has been established, that the isolates, which, after a long existence in a saprotrophic conditions, retained a high activity, and they form an active symbiotic soybean nodule apparatus, are virulent, have high nitrogen activity, mark a considerable amount of leg-hemoglobin in the nodules of soybean roots, are characterized by high the synthesis of EPS, with significant rheological properties. Thanks to the ability of the isolates to synthesize EPS with significant rheological features and increase the adhesive properties of crops, which allow them to be stored longer in the culture fluid and on the surface of soybean seeds. It can be assumed, that the ability of the nodule bacteria isolates to substantial development of the EPS may increase their adaptation and survival in the soil of various biocenoses.It has been established, that in the chernozem soils of the Forest-steppe of Ukraine there are highly active isolates of Bradyrhizobium japonicum, that adapted to saprotrophic existence, but did not lose their ability to ensure the formation and effective functioning of the symbiotic system with soybean plants Glycine max (L.) Merrill.
The existence of highly active isolates of Bradyrhizobium japonicum adapted to saprotrophic existence in the chernozem soils of the Forest-Steppe of Ukraine and their ecological and biological properties, ensuring the formation and effective functioning of the symbiotic system with soybean plants of Glycine max (L.) Merrill, promotes an increase in yield and seed quality.
It was established, that the usage of the B. japonicum LG 5 and LG 2 isolates conduced the formation of 1.29 and 1.33 m2 of the absorbing surface of the soybean roots, which were at the level of the absorbing surface formed with using the Rizoaktiv preparation.
The possibility of seed inoculation with B. japonicum LG 2 and LG 5 isolates has been studied, after they have been treated by Maxim, Vitavax 200 FF and Redigo M, because they do not reduce the inoculation of the inoculum load on soybean seeds by pre-treatment. Moreover, the use of culture broth of B. japonicum LG 5 isolate with a high content of EPS with significant rheological parameters were more resistant to the action of pesticides.
Thanks to the analysis of chernozem soils, highly effective isolates of nodule bacteria Bradyrhizobium japonicum LG 2 and LG 5 were obtained, which can be used as a basis for the production of a microbial preparation of nitrogen fixing soybean bacteria to increase the yield and quality of soybean seeds. It was found, that the use of B. japonicum LG 5 and LG 2 isolates of contributed to the formation of a significant absorption surface of the roots, was at the level of the absorption surface formed whith usage of the Rizoaktiv preparation. Under field conditions, it was also shown, that after pre-sowing treatment of soybean seeds with a culture of B. japonicum LG 5 isolate, nitrogenase activity of the nodules les increased by 20.4% relative to pre-sowing treatment with a standard and was equal to 1.18 nmol C2H4 formed per plant per hour, and when using strain LG 2, it was 1.05 nmol C2H4 formed per plant per hour, which is 7.1% more than the standard (Rizoaktiv preparation). For the first time competitive highly active Bradyrhizobium japonicum LG 2 and LG 5 isolates, which were isolated from chernozem soil and which retained the ability of active symbiotic interaction with Glycine max (L.) Merrill, namely, the nitrogenase activity of nodules on soybean roots 2.07 and 2.18 nmol/plant/h, nodulating ability of 31.5 and 38.6 nodules per plant, content of leghemoglobin – 0.565 and 0.658 mg/g, accordingly. They contributed to an increase in yield of 0.5–0.6 t/ha compared with the control. Whith usage of the isolates Bradyrhizobium japonicum LG 5, the yield increased by 4.4% compared to the standard.
