Effect of interaction between arbuscular mycorrhizal fungi and Rhizobium on Medicago sativa rhizosphere soil bacterial community structure and PICRUSt functional prediction

Abstract:

[Background] Medicago sativa is excellent leguminous forage that can reciprocate with arbuscular mycorrhizal (AM) fungi and rhizobium. Inoculation of AM fungi and rhizobium can promote soil nitrogen and phosphorus cycling and increase alfalfa yield. [Objective] To study the effects of AM fungi and Rhizobium on the structure and function of rhizosphere bacterial community. [Methods] Rhizosphere and non-rhizosphere soil samples of six different treatment groups were collected, based on the high-throughput sequencing technology of bacterial 16S rRNA gene V3?V4 region. The bacterial diversity and community distribution in the rhizosphere and non-rhizosphere soils of different inoculation treatment groups were analyzed and compared. PICRUSt software was applied to predict the function of bacterial microbiota between different treatment groups. [Results] A total of 3 849 OTU were obtained from 36 soil samples, belonging to 398 species of 50 divisions, 59 classes, 132 orders, 249 families and 595 genera. The main dominant bacteria were Proteobacteria (66.79%, 52.81%?81.46%), Bacteroidetes (7.83%?19.68%) and Actinobacteria (2.21%?16.40%). Compared with no inoculation, the inoculation treatment of Glomus intraradices and G. mosseae increased the beneficial bacteria of Gammaproteobacteria and Bacteroidia, inoculation with Rhizobium increased the abundance of the nitrogen-fixing bacteria Alphaproteobacteria. PICRUSt function prediction analysis indicateed that the bacterial microbiota had a total of 35 sub-functions. Inoculation with rhizobium can increase amino acid metabolism, which is conducive to plant N-nutrient cycle, and inoculation with AM fungi may have a certain inhibitory effect on N-cycle. Compared with single inoculation with AM fungi, double inoculation with AM fungi and rhizobium treatment group had stronger carbohydrate metabolism, which was more beneficial to plant nitrogen and phosphorus cycle. [Conclusion] The inoculation with AM fungi and rhizobium can increase the abundance of different beneficial bacteria related to nitrogen and phosphorus cycle in alfalfa, the results provide a scientific basis for plant nutrient uptake, the increase of alfalfa yield and the development and utilization of bacterial fertilizer.