Dynamics of Bacterial Community Structure in the Rhizosphere and Root Nodule of Soybean: Impacts of Growth Stages and Varieties

Abstract

Bacterial communities in rhizosphere and root nodules have significant contributions to the growth and productivity of the soybean (Glycine max (L.) Merr.). In this report, we analyzed the physiological properties and dynamics of bacterial community structure in rhizosphere and root nodules at different growth stages using BioLog EcoPlate and high-throughput sequencing technology, respectively. The BioLog assay found that the metabolic capability of rhizosphere is in increasing trend in the growth of soybeans as compared to the bulk soil. As a result of the Illumina sequencing analysis, the microbial community structure of rhizosphere and root nodules was found to be influenced by the variety and growth stage of the soybean. At the phylum level, Actinobacteria were the most abundant in rhizosphere at all growth stages, followed by Alphaproteobacteria and Acidobacteria, and the phylum Bacteroidetes showed the greatest change. But, in the root nodules Alphaproteobacteria were dominant. The results of the OTU analysis exhibited the dominance of Bradyrhizobium during the entire stage of growth, but the ratio of non-rhizobial bacteria showed an increasing trend as the soybean growth progressed. These findings revealed that bacterial community in the rhizosphere and root nodules changed according to both the variety and growth stages of soybean in the field.

Bioprospecting and Challenges of Plant Microbiome Research for Sustainable Agriculture, a Review on Soybean Endophytic Bacteria

“…Interestingly, research on rhizosphere microbiome with the view of mapping out strategies for their incorporation into agriculture has been emphasized in recent times [ 107 – 109 ]. Nevertheless, the presence of pathogens may influence rhizosphere microbes in many ecological processes.…”

Non-rhizobial nodule endophytes improve nodulation, change root exudation pattern and promote the growth of lentil, for prospective application in fallow soil

“…This study found fewer nitrogen-fixing genes in the rhizospheric region compared to the uninoculated control. According to Sohn et al. (2021) , nitrogen-fixing genes are more prevalent in the plant’s later stages.…”

Long-term fertilization coupled with rhizobium inoculation promotes soybean yield and alters soil bacterial community composition

“…First, this may be because the inoculation of rhizobia inhibits the growth of other bacteria, leading to the enrichment of rhizobia in the soybean rhizosphere soil. Secondly, rhizobium can symbiosis nitrogen fixation with soybean, and soybean growth slows down after entering the maturity stage compared with the earlier stages, resulting in a decrease in bacterial abundance ( Sohn et al, 2021 ). Third, crop roots mainly stimulate specific rhizosphere groups, resulting in communities that become increasingly different from the bulk soil, often with lower diversity ( Shi et al, 2015 ; Fan et al, 2017 ; Nuccio et al, 2020 ).…”