The dynamics of the nitrogen fixation activity of the root nodules, the growth of the vegetative mass of plants and the change in the activity of antioxidant enzymes (superoxide dismutase, ascorbate and guaiacol peroxidase) in different soybean organs for treatment of seeds by rhizobia incubated with lectin, in combination with fungicides have been studied. The objects of the study were symbiotic systems formed with the participation of soybean (Glycine max (L.) Merr.) Almaz and Bradyrhizobium japonicum (standard strain 634b) incubated with lectin. As disinfectants of soybean seeds, the following preparations with fungicidal activity were used – Maxim XL 035 PS, Fever, Standak Top according to one rate of active substance consumption of each preparation specified by the manufacturer. One part of the seeds treated with fungicides was inoculated with pure culture of suspension of rhizobia for one hour (titre of suspension concentration was 108 cells/ml). Another part of the seeds treated with fungicides was inoculated with rhizobia suspension, which was previously incubated with a solution of commercial lectin soybean at a concentration of 100 μg/ml. The research was conducted in strictly controlled conditions of a model vegetative experiment using microbiological, physiological, biochemical methods, gas chromatography, spectrophotometry. It was found that processing of soybean seeds with fungicides (Fever and Maxim XL) together with rhizobium inoculation contributed to the preservation of the nitrogen fixation activity of the root nodules and the growth of vegetative mass of plants. Under these conditions, the intensification of the activity of superoxide dismutase and ascorbate peroxidase was observed, as well as inhibition of the activity of guaiacol peroxidase in soybean root nodules in the phase of three true leaves and increased activity of all investigated enzymes in the phase of mass flowering. It has been established that the use of complex treatment of seeds by soybean rhizobia incubated with lectin and fungicides leads to an increase in the activity of superoxide dismutase and guaiacol peroxidase in root nodules in the phase of three true leaves and the growth of the activity of ascorbate peroxidase in the phase of mass flowering. At the same time, the inhibition of the growth of vegetative mass of plants and their symbiotic properties occurred, as evidenced by the decrease in the nitrogen fixation activity of the root nodules for the joint treatment of seeds with fungicides and lectin. A specific reaction of investigated enzymes in the roots and leaves of soybean was shown, which was more pronounced in the phase of three true leaves, indicating the development of a typical antioxidant reaction to a complex treatment, as a kind of stress that is leveled to the phase of mass flowering. The degree of reaction of antioxidant enzymes in the studied symbiotic systems Glycine max – Bradyrhizobium japonicum depends on the nature of the active substance fungicides and the manifestation of their joint effect in a complex with rhizobia incubated with lectin.
Enhancement of symbiotic nitrogen fixation activity of Bradyrhizobium japonicum by acridine orange.