Effects Of Root Exudates On Rhizosphere Bacterial Community During Soybean Growth

The compounds released by plant roots are considered to be the key factors shaping the rhizosphere microbial community,which directly or indirectly affects plant health and nutrient absorption.So far,there have been relatively few studies on the changes of root exudates during soybean growth,and the effects of soybean root exudates on rhizosphere microorganisms.In this paper,soybeans grown under greenhouse conditions are used as the research object.Through high-throughput 16 S r DNA amplicon sequencing technology and Un-targeted Metabolomics analysis,the following three aspects of research are mainly carried out: 1.The succession pattern of the bacterial community over time;2.The characteristics of the changes of the components of root exudates with time during the growth of soybean;3.The role of root exudates in the construction of rhizosphere bacterial communities.The results are as follows:The structure of the rhizosphere bacterial community is different from that of the bulk soil,and has unique temporal succession characteristic.In the process of soybean growth,the construction of the rhizosphere bacterial community can be divided into two stages,the first stage(1-5 weeks)of the bacterial community is regarded as "Excessive bacterial community",the second stage(5-11 weeks)is regarded as "Stable bacterial community".Proteobacteria,Acidobacteria,Bacteroidetes in the rhizosphere occupied relatively high abundance throughout the growth of soybean,and the relative abundance of these three phylums changed significantly in the first stage of community construction,while in the second stage Proteobacteria with the highest relative abundance did not change significantly.Soybean root exudates also have a clear temporal succession law.Most compounds belong to terpenoids,fatty acyls,carbohydrates,flavonoids,organic acids,these exudates have the largest accumulation in the fifth and seventh weeks of soybean growth.the compounds that are highly correlated with the changes in the composition of the first stage of exudates are flavonoids and carbohydrates,and the compounds that are highly correlated with the changes of the composition of the exudates of the second stage are terpenoids.There is a significant correlation between exudates and bacterial communities during soybean growth.The effects of root exudates on rhizosphere bacterial communities mainly include "reconstruction" and "stability".The main function of root exudates during the "reconstruction" process are repellanted and enriched microorganisms.During the "stabilization" process,the exudates fine-tune the already established rhizosphere microbiome.Its main function is to serve the plant itself and help the plant absorb nutrients,defense against pathogenic microorganisms and allelopathy etc.This study provides a theoretical basis for the assembly process of rhizobacteria in the process of soybean growth,and provides a direction for the manipulation of rhizosphere bacterial communities through exudates,thereby helping to solve practical problems such as plant diseases and continuous cropping obstacles.