Ecological adaptation and phylogenetic analysis of microsymbionts nodulating Polhillia, Wiborgia and Wiborgiella species in the Cape fynbos, South Africa

Tiisetso Mpai,Sanjay K Jaiswal,Christopher N Cupido,Felix D Dakora

doi:10.1038/s41598-021-02766-2

Tiisetso Mpai, Sanjay K Jaiswal + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-02766-2

Copy DOI

Abstract

Polhillia, Wiborgia and Wiborgiella species are shrub legumes endemic to the Cape fynbos of South Africa. They have the ability to fix atmospheric N2 when in symbiosis with soil bacteria called ‘rhizobia’. The aim of this study was to assess the morpho-physiological and phylogenetic characteristics of rhizobia associated with the nodulation of Polhillia, Wiborgia and Wiborgiella species growing in the Cape fynbos. The bacterial isolates from root nodules consisted of a mixture of fast and intermediate growers that differed in colony shape and size. The isolates exhibited tolerance to salinity (0.5–3% NaCl) and pH (pH 5–10) and different antibiotic concentrations, and could produce 0.51 to 51.23 µg mL−1 of indole-3-acetic acid (IAA), as well as solubilize tri-calcium phosphate. The ERIC-PCR results showed high genomic diversity in the rhizobial population and grouped them into two major clusters. Phylogenetic analysis based on 16S rRNA, atpD, glnII, gyrB, nifH and nodC gene sequences revealed distinct and novel evolutionary lineages related to the genus Rhizobium and Mesorhizobium, with some of them being very close to Mesorhizobium australicum. However, the phylogenetic analysis of glnII and nifH genes of some isolates showed incongruency.

Highlights

Polhillia, Wiborgia and Wiborgiella species belong to the family Leguminosae and tribes Genisteae and Crotalarieae[1,2,3]
The aim of this study was to evaluate the morpho-physiological diversity and phylogeny of bacterial symbionts associated with the nodulation of Polhillia, Wiborgia and Wiborgiella species
The original host plants (Polhillia pallens and Wiborgia obcordata) were able to nodulate with rhizosphere soil suspensions from their respective sites of collection. (Table S2)

Summary

Introduction

Wiborgia and Wiborgiella species belong to the family Leguminosae and tribes Genisteae and Crotalarieae[1,2,3]. They are endemic to the Cape fynbos biome, recognized as one of the richest areas of flowering plants in the w orld[4,5,6]. These legumes have bright yellow and/or white flowers, which are a major attraction for tourists[3,7]. The following questions were addressed (1) Which rhizobial species nodulate these wild shrub legumes? (2) What are the phylogenetic behaviours of the isolates?

Objectives

Methods

Results

Discussion

Conclusion