Effect of arbuscular mycorrhizal fungi and rhizobium inoculation on soil fungal community structure and function in the rhizosphere of Medicago sativa

In China, the yield of Medicago sativa, an excellent legume forage, has been in short supply. Inoculation with AM fungi and rhizobium can promote soil nitrogen and phosphorus cycling and increase stress resistance to increase M. sativa yield. In order to investigate the effects of AM fungi and Rhizobium on the structure and function of rhizosphere fungal community, in this experiment, the rhizosphere and non-rhizosphere soil samples of six different treatment groups (Without inoculation,only inoculation with Glomus mosseae, only inoculation with Glomus intraradices, only inoculation Sinorhizobium meliloti, double inoculation with Glomus intraradices and Sinorhizobium meliloti, double inoculation with Glomus mosseae and Sinorhizobium meliloti) were collected, based on the high-throughput sequencing technology of the fungal ITS region, the laws of fungal diversity and community distribution in the rhizosphere and non-rhizosphere soils of M. sativa in different inoculation treatment groups were analyzed and compared, the FUNGuild software was used to predict the flora function between different treatment groups. The results show, in 6 different treatment groups, the soil fungal community was mainly composed of Ascomycota and Basidiomycota, with Ascomycota as the main species (19.29%～61.18%). It was found at the genus level that inoculation with AM fungi and rhizobium significantly increased the abundance of beneficial fungi compared with no inoculation. For example, the dominant genus in the inoculation with Glomus mosseae GMR treatment group was Acremonium, and the dominant genus in the only inoculation Sinorhizobium meliloti KR treatment group were Stachybotrys and Trichurus, the dominant genus in the double inoculation with Glomus intraradices and Sinorhizobium meliloti GIKR treatment group was Trichoderma, and the dominant genus in the double inoculation with Glomus mosseae and Sinorhizobium meliloti GMKR treatment group was Aspergillus. And inoculation with AM fungi and rhizobium significantly increased the OTUs, Shannon index, and Chao1 index of the fungal community. Among different inoculation treatments, saprophytic types were dominant type. Inoculation of AM fungi and rhizobia increased the relative abundance of symbiotic types and decreased the relative abundance of pathogenic types. To sum up, the inoculation of AM fungi and rhizobia is conducive to the circulation of soil nitrogen and phosphorus, increases the richness and diversity of soil fungal community, increases the abundance of biocontrol bacteria, nitrogen fixation and phosphorus solubilizing bacteria, increases the relative abundance of symbiotic type, and reduces the relative abundance of pathogenic type. Therefore, inoculation with AM fungi and rhizobium enriched fungal community composition and optimized the original microbial ecological environment, which was beneficial to the improvement of M. sativa quality and yield.