Estimation of stability of soybean root nodule bacterial strains to the recommended chemical fungicides

The work determines the resistance of various strains of soybean nodule bacteria to the recommended chemical fungicides in the tank solution applied to the seed surface. As experimental rhizobia there were studied such soybean bacteria of the Bradyrhizobium japonicum of the following strains as 634b, 640, BR-648, BR-733. The fungicides “Maksim”, “Protekt”, “Protekt Forte” were used as disinfectants. In the tank solution there was determined compatibility by mixing the biopreparation and the disinfectant, keeping the mixture at room temperature in the dark, with further determining percentage of the survived rhizobia depending on the disinfectant type and the keeping time of the solution. It has been established that different soya rhizobia strains do not practically differ in resistance to disinfectants in the tank solution. However, the disinfectants possess different degrees of toxicity to the studied strains, which made it possible to arrange the disinfectants due to their increasing toxicity for rhizobia “Maksim”, “Protekt”, “Protekt Forte”. Since the strains taken for the study practically did not differ in their resistance to disinfectants in the tank solution, there was investigated only the strain B. japonicum 634b to determine the dynamics of rhizobia death on the treated seeds. Determination of the disinfectants' toxicity was carried out by placing the washes from treated seeds on the plates with nutrient medium. The treated seeds were kept at room temperature in the dark. The selection of the treated seeds was carried out after 2, 4 and 8 hours after treatment. The nature of the curves for rhizobia reduction on seeds showed that “Protekt Forte” was the most toxic to bacteria on the seed surface, and “Maksim” was the most “soft”. This study will allow optimizing the process of soybean seeds inoculation with their simultaneous treatment with chemical disinfectants.

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