ASSESSMENT OF THE FUNGICIDAL SEED TREATMENTS INFLUENCE ON THE SOYBEAN SYMBIOTIC APPARATUS FORMATION

The article presents the results of laboratory studies of the effect of the fungicidal seed protectants Delti Pro (pyraclostrobin) and Maxim (fludioxonyi) on the formation of the symbiotic apparatus of soybeans when combined with inoculants based on strains Bradyrhizobium japonicum (Jordan, 1982), Sinorhizobium fredii (Scholla, Elkan, 1984), Bradyrhizobium elkanii (Kuykendall et al., 1992). The experiments were carried out using the Kinbarovsk 4 soybean variety and collection strains of rhizobia isolated from natural populations of the Far Eastern region of Russia and the border regions of China. It was found that simultaneous treatment of seeds with mordants and rhizobia in most cases reduces nodule formation rates: on average by 2 times for Deltipro and 1.5 times for Maxim compared with the control. The virulence of the strains decreased by 16% and 7%, respectively. However, individual strains (B. japonicum MM-140, S. fredii OB-46, B. elkanii 11554, Wu-15) demonstrated resistance to mordants, maintaining or increasing the intensity of nodule formation (by 18–84%). The dependence of the effect of mordants on virulence on a specific strain has been revealed. The results emphasize the need to develop regulations for the combined use of inoculants and pesticides to optimize seed treatment technologies.