Efficacy of soybean inoculation by biopreparations based on fungicide-resistant rhizobium strains under seed treaters impact

The effectiveness of soybean inoculation with pesticide-resistant nodule bacteria strains Bradyrhizobium japonicum PC07 and PC10 on the background of pre-sowing seed treatment with Maxim XL, Standak Top and Fever was studied in pot experiments. Under the influence of fungicide Maxim XL, the number and weight of nodules, the weight of the aboveground part of plants and soybean roots exceeded the control plants throughout the growing season in variants with bacterization of both rhizobia strains. Fever had a depressing effect on soybean plants, and their interaction with nitrogen-fixing microorganisms. Under the action of this preparation there was a decrease in the root nodules number by 8.0—30.2 %, an increase in aboveground mass by 6.8—18.9 %, and root mass by 13.2—21.3 %. With the combined use of all seed treaters and nodule bacteria, there was a decrease in the level of N 2 assimilation at the stage of three true leaves. At the budding-beginning of flowering stage under inoculation of soybean seeds with B. japonicum PC10 on the background of fungicide application, the indices of nitrogen-fixing activity were higher by 4.4—22.7 % in compari-son with control plants. At the bean formation stage in the variants with seed treatment with Maxim XL and Standak Top, it was observed the highest nitrogen fixation by nodules formed with the participation of B. japonicum PC07 and PC10, which exceeded the indices of control plants by 1.8—3.9 times. When seed treatment with Fever was combined with bacterization by B. japonicum PC07, the negative influence on the functioning of the symbiotic apparatus throughout the soybean vegetation affected the level of crop productivity. Under the application of pesticides Standak Top and Maxim XL and inoculation of B. japonicum PC07 and PC10, soybean grain productivity increased by 9.5—25.8 %, due to the tolerance of the formed symbiotic systems to the active substances in these pesticides. Thus, the use for soybean seed treatment of bacterial preparations based on rhizobia strains resistant to modern fungicides will help reduce the effects of chemical stress on the symbiotic systems formation and functioning. In turn, maintaining the efficiency of plant-microbial systems combined with the implementation of seed treaters prophylactic action create the precondi-tions for increasing plant productivity.