Production of Phytohormones of Bradyrhizobium Japonicum and Azospirillum Brasilense Under Their Simultaneous Cultivation

Abstract

Objective. Investigate the activity of biosynthesis of phytohormonal substances with nitrogen-fixing bacteria Bradyrhizobium japonicum and Azospirillum brasilense in pure and mixed culture.
 Methods. Microbiological, chromatographic, and mathematical.
 Results It has been established that the simultaneous cultivation of B. japonicum M-8 and A. brasilense 410 increases the content of gibberellins and cytokinins in the culture fluid of the test microorganisms. The content of gibberellic acid and isopentenylidene has increased most intensively in mixed culture compared with the pure culture of rhizobia. In the course of co-cultivation, the studied diazotrophs more intensively produced auxins compared to soybean rhizobia in pure culture, but less compared to pure culture of azospirilla. The highest level of abscisic acid that can inhibit the formation of nodules was found in A. brasilense 410 culture fluid, and it was lower when cultivating B japonicum M-8. However, the smallest amount of this phytohormone was found in the culture liquid of diazotrophs under their co-cultivation. The lowest ratio of auxin/cytokinin was found in B. japonicum M-8 and A. brasilense 410 culture fluid under their co-cultivation, which should positively influence the formation of a symbiotic system when interacting with soybean plants.
 Conclusion. A combination of cultivating rhizobia and azospirilla showed an increase in the amount of cytokinins and gibberellins in the culture fluid of the microorganisms, a decrease in the amount of abscisic acid and improvement in the auxin/cytokinin ratio compared to the values of the pure cultures of the nitrogen-fixing bacteria studied. An analysis of the quantitative parameters of the content of phytohormones suggests the feasibility of combining B. japonicum and A. brasilense in a mixed culture for the effective introduction of rhizobia in soybean agrocenosis.

Symbiotic Efficiency and Cytokinin Activity of New Mesorhizobium cicerі Strains

“…Some studies have shown that nodule bacteria of legumes in pure culture can produce auxins, cytokinins, gibberellins, and other phytohormonal substances [6,7]. Here is information about direct lines correlations between symbiotic activity and the ability of bacteria to actively synthesize cytokinins [8].…”

“…It is known that rhizobia strains are capable of synthesizing extracellular cytokinins involved in the regulation of cell division processes, which initiates the formation of root nodules [1][2][3][4][5][6][7][8]20].…”