EFFICACY OF THE ASSOCIATION “SPRING WHEAT – AZOSPIRILLUM BRАZILENSE B-7318”

Abstract

Objective. To evaluate the ability of Azospirillum brasilense B-7318, a bacterium that intensively fixes molecular nitrogen, to form stable effective associations with spring wheat plants. Methods. Microbiological, application (to determine the intensity of azospirilla development in the root spheres of plants), acetylene (to study nitrogenase activity), phosphate (to determine the activity of glutamine synthetase in plant leaves), field experiment, statistical. Results. A new strain of A. brasilense B-7318, capable of intensively fixing molecular nitrogen, was obtained by the method of analytical selection. It was shown that inoculation of spring wheat seeds results in effective colonization of the surface of roots and the rhizosphere soil by diazotrophs during inoculation of spring wheat seeds (the highest density of bacteria was registered up to 2 mm from the root surface). Potential nitrogenase activity in the rhizosphere soil when A. brasilense B-7318 was used for inoculation didn’t significantly different from the values of the control variant (without inoculation). At the same time, potential nitrogenase activity on the washed roots of inoculated plants significantly (by 4.9 times) exceeded this parameter in the rhizoplane of plants of the control variant. A. brasilense B-7318 also contributes to a significant increase in glutamine synthetase activity in the leaves of wheat plants (by 57 %). When wheat seeds were inoculated with A. brasilense B-7318 bacterial suspension, the protein content in plant leaves increased by 9.7 %. The results of determining the structure of the crop in the field experiment proved that azospirilla provided a significant increase in the length of the ear (by 8.1 %), the number of grains in the ear (by 4.1 %), the mass of grains from the ear (by 14.8 %) and the weight of 1,000 grains (by 6.1 %), as well as an increase in yield by 15.7 % compared to the control. Conclusion. A. brasilense B-7318, which is characterized by high nitrogenase activity in pure culture, is able to actively colonize the root spheres of spring wheat plants, increase glutamine synthetase activity and protein content in leaves, as well as contribute to the increase of potential nitrogenase activity on plant roots and improvement of the wheat yield.