Construction And Function Of Characteristic Rhizosphere Microflora Of Soybean At Different Growth Stages

The use of agricultural microorganism can reduce the dependence of agricultural production on chemical fertilizer and pesticide and contribute to the green and sustainable agriculture.Identifying the composition,construction mechanism and ecological function of rhizosphere microorganisms in different growth stages of soybean can provide a good theoretical basis for screening and utilizing beneficial bacteria in soybean root system.Although some studies have shown that rhizosphere microbiome succession occurs with the growth of soybean,its succession mode and driving mechanism are still unclear,and there are no reports on the different effects of microbial community in different stages of succession on plant growth.In this study,through 16 S r RNA gene high-throughput sequencing,metabonomics and culturomics,the succession pattern of rhizosphere bacterial community in different growth stages of soybean Zhonghuang13 was explored,and the influence of changes in root exudate composition on community succession was analyzed.Artificial rhizosphere bacterial communities were constructed in the bulk soil and soybean at different growth stages and their functions were investigated.The main conclusions are as follow:1.There were significant differences in the structure of rhizosphere bacterial community between the original soil and soybean,and the rhizosphere bacterial community showed obvious succession with the growth period of soybean.Among them,the time sequence variation of the rhizosphere bacterial community in the week1-5 was great,and then gradually stabilized in the week5-7.Proteobacteria,Actinobacteria,Gemmatimonadetes,Acidobacteria,Bacteroidetes,Firmicutes and other groups changed significantly during the succession.It also plays an important role in the composition and network structure of rhizosphere flora.The root exudates of soybean showed significant characteristic differences during growth period,which regulated the succession process of bacterial community structure.Compared with down-regulated secretions,the up-regulated secretions had a higher correlation with rhizosphere bacterial flora during growth period.Among them,flavonoids,amino acids,organic acids and their derivatives were the key secretions types.2.The cultureomics strategy was used to construct the characteristic rhizosphere bacterial strains in the bulk soil and in each growth period.The total number of strains was10056,which could cover 41.12% of the high throughput sequencing results with relative abundance greater than 0.1%ASV(amplicon sequence variantat)at genus level,the bacterial strains could better reproduce the period succession pattern of the rhizosphere community.Biolog experiment showed that organic acids,sugars played an important role in the construction and succession of rhizosphere flora.Plant experiments showed that the rhizosphere flora at different stages had different ability to promote plant growth.In the early stage,the rhizosphere strains mainly promoted nodule formation,then gradually turned to promote plant growth.In conclusion,soybean rhizosphere bacterial community could be regulated by root exudates in order to meet the needs of different growth stages.This experiment provides a new sight for exploring the regulation of rhizosphere community by specific root exudates,provides a theoretical basis for directional screening of specific functional bacteria,and also provides a resource basis for the construction of simplified artificial synthetic Syncom in the future.