The Root Nodule Microbiome of Cultivated and Wild Halophytic Legumes Showed Similar Diversity but Distinct Community Structure in Yellow River Delta Saline Soils.

Yanfen Zheng,Jing Liang,Zong-Chang Xu,Dong-Lin Zhao,Zhi-Hong Xie,Cheng-Sheng Zhang,Chen Meng

doi:10.3390/microorganisms8020207

Abstract

Symbiotic associations between leguminous plants and their nodule microbiome play a key role in sustainable agriculture by facilitating the fixation of atmospheric nitrogen and enhancing plant stress resistance. This study aimed to decipher the root nodule microbiome of two halophytic legumes, Sesbania cannabina and Glycine soja, which grow in saline soils of the Yellow River Delta, China, using PacBio’s circular consensus sequencing for full-length bacterial 16S rRNA gene to obtain finer taxonomic information. The cultivated legume Glycine max was used for comparison. We identified 18 bacterial genera and 55 species in nodule samples, which mainly classified to Proteobacteria, and rhizobial genus Ensifer was the predominant group. The three legumes showed similarity in operational taxonomic unit (OTU) diversity but distinction in OTU richness, indicating that they harbor similar bacterial species with different relative contents. The results of principal coordinates analysis and ANOSIM tests indicated that G. soja and G. max have similar nodule bacterial communities, and these communities differ from that of S. cannabina. Wild legumes S. cannabina and G. soja both harbored a higher number of rhizobia, while G. max possessed more non-rhizobial bacteria. These differences could be associated with their adaptability to saline–alkali stress and revealed clues on the nodule endophytes with relative importance of culturable rhizobial symbionts.

Highlights

Soil salinization is one of the major abiotic factors reducing crop productivity worldwide, and it is estimated that there is currently approximately one billion hm2 of salt-affected soils distributed across more than 100 countries [1]
We were able to compile a directory listing the endophytic nodule bacteria at the species level associated with three legumes (S. cannabina, G. soja, and G. max) planted in saline soil based on high-throughput sequencing
Large amounts of rhizobia were found in S. cannabina (100%), G. soja (95.62%), and G. max (85.80%)

Summary

Introduction

Soil salinization is one of the major abiotic factors reducing crop productivity worldwide, and it is estimated that there is currently approximately one billion hm of salt-affected soils distributed across more than 100 countries [1]. As a typical representative of the coastal saline soils of China, the soil of the delta has a high salt content, low organic matter content, and is nitrogen deficient. Studies have shown that utilization of salt-tolerant plants is a new and promising approach for the improvement of saline–alkaline soils. In this regard, symbiotic nitrogen-fixing legume plants, which are characterized by the formation of root nodules, could grow well in saline-affected soils [4]. Et Zucc are annual legumes and included in the list of Halophytes of China [5] Owing to their characteristic features of high productivity, salt tolerance, and adaptation to nutrient-deficient environments, they have been considered as ideal candidate plants for coastal saline soil improvement

Objectives

Results

Conclusion