Effects of rhizobial inoculation, cropping systems and growth stages on endophytic bacterial community of soybean roots

Abstract

The effects of rhizobial inoculation, soybean-maize intercropping and plant growth stages on the diversity of soybean root endophytic bacteria were evaluated. PCR-based terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes and analyses of cloned partial 16S rRNA gene libraries were used to study the endophytic bacterial communities. The root endophytic bacterial populations during the whole growing season was significantly affected by the three factors analyzed, with plant growth and rhizobial inoculation showing the highest and lowest impact. The alphaproteobacteria and betaproteobacteria were the most predominant endophytes of soybean roots. Some undefined bacterial lineages were also found, indicating that the root endophytic populations might constitute an important source for the isolation of novel bacteria. Bradyrhizobium liaoningense (used as inoculant) occupied most of the soybean nodules formed and Sinorhizobium americanum-related bacteria were detected as the main root endophytes. Results also suggest that bacteria might be transferred from nodules to roots (as endophytic bacteria) when the seeds become mature, which might be a possible process in the life cycle of rhizobia. Rhizobial inoculation and intercropping practices could increase the diversity of the soybean root endophytes, which might have a positive influence on the growth of soybean plants.

Spatial and Temporal Variation of Cultivable Communities of Co-occurring Endophytes and Pathogens in Wheat

“…Altogether, these results show that temporal variations were mainly driven by the succession of pathogens. Previous studies indicated significant differences in bacterial populations over the seasons in roots and leaves of soybean and rice (Mano et al, 2007 ; Zhang et al, 2011 ). Likewise, temporal variations in fungal endophytes communities have already been observed in cotton (Ek-Ramos et al, 2013 ), and in several wild plants including trees and herbaceous grassland plants (Mishra et al, 2012 ; Wearn et al, 2012 ; Zimmerman and Vitousek, 2012 ).…”

Microbial Inoculants and Their Impact on Soil Microbial Communities: A Review

“…The effects of growth stage, intercropping, and rhizobial inoculation on diversity of soybean endophytic bacteria were demonstrated by the cluster analysis of terminal restriction fragments and the redundancy analysis [49]. The relative abundance in roots was enhanced for Bradyrhizobium liaoningense and decreased for Sinorhizobium americanum , demonstrating that the endophytic Sinorhizobium might be suppressed by competition from the introduced strain.…”

“…The difference in abundance of endophytic Sinorhizobium , Bradyrhizobium, and Rhizobium in the soybean roots could be correlated to the nodulation autoregulation system of legumes, which is capable of sensing and responding to the presence of inefficient rhizobia by applying sanctions to inactive strains via active control of the permeability of root cortical cells to oxygen, thus limiting the growth of inefficient nodules [20]. A 517 bp TRF assigned to Comamonadaceae and Burkholderiales showed a higher abundance in inoculated soybeans [49]. The abundance of rhizosphere Comamonadaceae bacteria has been previously reported to be associated with mycorrhization [50], and, on the other hand, the latter could be stimulated by the rhizobial inoculation of soybean [51].…”

Endophytic Microbiota Comparison of Dendrobium huoshanense Root and Stem in Different Growth Years

“…Accordingly, the growth year is an important cause of constituents to D. huoshanense. There are differences in the diversity of endophytic bacteria of balloon flower on the basis of the plantsʼ age [14]. Plant growth drives succession in the rhizosphere community [15].…”