Comparison of the variability and nitrogen-fixing activity of rhizobia strains isolated from Trifolium Hybridum L. and Galegaorientalis Lam. nodules at different stages of plant vegetation

BACKGROUND: The beginning of the life cycle of a leguminous plant in its natural habitat is usually associated with interaction with nodule bacteria in order to form a nitrogen-fixing symbiosis. In a short period of time, a plant needs to “choose” suitable microsymbionts for itself. Since a wide variety of rhizobial strains is formed in the rhizosphere of legumes, the choice made by the macrosymbiont will further influence its productivity. AIM: The purpose of our work was to compare the principles of selection by different plants of their microsymbionts at different stages of plant development. MATERIALS AND METHODS: Nodule bacteria Trifolium hybridum L. and Galegaorientalis Lam. were taken into the study. Their genetic diversity was studied by the RAPD method, a phylogenetic analysis of bacteria and their symbiotic nodC and nifH genes was carried out, and their nitrogen-fixing activity was assessed. RESULTS: It was found that the rhizobia that form nodules on the roots of the studied leguminous plants at different stages of their vegetation have certain patterns. It was found that the highest polymorphism and specific nitrogen-fixing activity are characteristic of bacteria obtained from nodules formed at the initial stage of vegetation. CONCLUSIONS: We assume that the plasticity of the rhizobia genome gives the host plant the ability to more flexibly adjust its nitrogen-fixing apparatus to changes in growing conditions.