| As the driving force for transforming material and energy,soil microbiome also play a vital role in plant growth.The soil microbes can enter the leguminous plant rhizosphere,root and nodule endosphere.During this process,the structure,distribution and the influential factors are still unclear.This study was focused on the symbiotic nitrogen-fixing system and the composition and structure of nodule endophytes,root endophytes,rhizosheric microbiome and root zone microbiome by high-throughput sequencing was analyzed.The influences of environmental factors on nodule endophytes and rhizosphere microbiome were demonstrated.The enrichment process of the nodule endophytes was explored by comparing the composition and structure of the microbiome of bulk soil and root associated microbiome.The potential plant growth promoting rhizobacteria were identified.The influences of leguminous plant on the rhizospheric microbiome of leguminous plants were explored by split-root experiment.The results were as follows:By analyzing the composition and structure of the nodule endosphere microbiome of soybean and alfalfa,the results revealed that Ensifer and Bradyrhizobium were the main soybean nodule endophytes,and Ensifer was the main alfalfa nodule endophytes.A small number of Rhizobium and Mesorhizobium were also detected in the nodule endophytes.Various non-symbiotic bacteria were detected in the nodule endophytes,mainly in Proteobacteria,Actinobacteria,Firmicutes and Bacteroidetes.There were significant differences between the composition of non-symbiotic nodule endophytes and root endophytes.The greatest explanation of the variance of rhizobium was plant species,and next the soil nitrogen content,pH and plant growth stages.The greatest explanation of the variance of non-symbiotic nodule endophytes was plant species,and next the soil nitrogen and phosphorous content,while plant growth stages exhibited no significant influence.By comparing the composition and structure of the microbiome of root associated microbiome,the alpha diversity and beta diversity of the microbiome of nodule endophytes,root endophytes,rhizospheric and root zone exhibited significant differences.The root zone,rhizospherie,root and nodule formed a spatial gradient from outer to inner,which assisted to reveal the hierarchical filtration of soil microbiome by plants.The influence of soil type on the root associated microbiome decreased from the outer to inner.The influence of plant species on the root associated microbiome decreased from the inner to outer.Soil pH,phosphorous and potassium content exhibited significant influence on the structure of rhizospheric microbiome,which showed significant influence on plant biomass.The relative abundance of Paracraurococcus,Treponema,Actinomadura,Actinopolymorpha,Desulfitobacterium and Nonomuraea showed significantly positive correlations with soybean biomass.The relative abundance of Ensifer,Thermobacillus,Acetivibrio,Pandoraea,Marmoricola,Rhodococcus,Gordonia,Turicibacter,Pimelobacter,Filifactor,Nocardioides,Frateuria and Aestuariimicrobium showed significantly positive correlations with alfalfa biomass.The results demonstrated that soil factors can influence not only the composition of whole rhizopsheric microbiome but also the relative abundance of plant growth promoting bacteria.By analyzing the composition and structure of rhizospheric microbiome of common bean(Phaseolus vulgaris L.)which grown in two types of soil in split-root experiment,the results suggested that split-root plant could reduce the differences between the rhizpsheric microbiome in two types of soil.A certain extent of homoplasy exhibited in the rhizpsheric microbiome in two types of soil by split-root experiment.The homoplasy of rhizospheric microbiome in Jiangxi soil was mainly in Proteobacteria,Planctomycetes,Bacteroidetes and Actinobacteria.The homoplasy of rhizospheric microbiome in Shaanxi soil was mainly in Proteobacteria,Planctomycetes,Firmicutes,Bacteroidetes,Chloroflexi,Actinobacteria and Acidobacteria.The relative abundance of nitrite-oxidizing bacteria,Ensifer and Mesorhizobium were significantly decreased when common bean was grown in two types of soil by split-root experiment,while the relative abundance of Bradyrhizobium was significantly increased.Our study revealed the existence of various nodule endophytes,which include rhizobium and non-symbiotic endophytes.The enrichment of the nodule endophytes was from soil microbiome by hierarchical filtration function of leguminous plants.The rhizospheric microbiome exhibited significant influence on plant biomass.A certain extent of homoplasy exhibited in the rhizpsheric microbiome in two types of soil by split-root experiment. |
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