Phylogenetic analyses of symbiotic genes and characterization of functional traits of Mesorhizobium spp. strains associated with the promiscuous species Acacia seyal Del.

Abstract

Aims: To assess the phenotypic, symbiotic and genotypic diversity scope of Mesorhizobium spp. strains associated with Acacia seyal (Del.) isolated from different agro‐ecological zones in Senegal, and uses of susceptible microbial inoculum in a reafforestation process. Methods and Results: A polyphasic approach including phenotypic and genotypic techniques was used to study the diversity and their relationships with other biovars and species of rhizobia. The geographical origins of the strains have limited effect on their phylogenetic and phenotypic classification. Nodulation tests indicated promiscuity of the strains studied, because they were capable of nodulating six woody legume species (Acacia auriculiformis, Acacia senegal, A. seyal, Acacia tortilis ssp. raddiana, Leucaena leucocephala and Prosopis juliflora). Sequencing and phylogenetic analyses of nodA, nodC and nifH genes pointed out that in contrast to nodA gene, the phylogenies of nodC and nifH genes were not consistent with that of 16S rRNA, indicating that these genes of the A. seyal‐nodulating rhizobia might have different origins. Microbial inoculation on nonsterile soil had significant effect on the nodules number and the growth of the seedlings, indicating that these strains of rhizobia might be used as inoculum. Conclusions: The results indicated that A. seyal is a nonselective host that can establish effective symbiosis with Mesorhizobium spp. strains from diverse genomic backgrounds and that the selected A. seyal‐nodulating rhizobia could enhance plant growth. Significance and Impact of the Study: These results showed the important role that A. seyal could play in the improvement of reafforestation process as a promiscuous host, which can establish effective symbiosis with rhizobia from diverse genomic backgrounds.

Phylogeny of Nodulation Genes and Symbiotic Diversity of Acacia senegal (L.) Willd. and A. seyal (Del.) Mesorhizobium Strains from Different Regions of Senegal

“…The authors demonstrated that these two Acacia species were mainly nodulated by Mesorhizobium plurifarium. Moreover, A. senegal and A. seyal species belong to the same crossnodulation group, as demonstrated by Diouf et al [13] in a study where Mesorhizobium spp. strains isolated from A. seyal were able to nodulate both A. senegal and A. seyal.…”

“…Unlike nodulation genes, the nif genes are found in a broad spectrum of phylogenetically unrelated bacteria besides rhizobia. Correlations between the phylogeny of nifH and that of 16S ribosomal RNA (16S rRNA) genes were reported [9], and it was proposed that nifH and 16S rRNA genes share a common evolutionary path [9][10][11][12][13].…”

A large diversity of non-rhizobial endophytes found in legume root nodules in Flanders (Belgium)

“…The majority of the investigated nodules contained Bacillus (17.9%), Paenibacillus (12.5%) and Pseudomonas (15.9%) NRE species, together with small numbers of other NRE bacterial genera from the classes Actinobacteria, Alpha-and Betaproteobacteria. Nodulation and nitrogen fixation capacity are characters usually studied in rhizobia research, since they give an indication of the host specificity and nitrogen fixing ability (Perret et al, 2000;Moulin et al, 2004;Diouf et al, 2010). No nodC or nifH gene sequences could be detected among the isolates, indicating an endophytic lifestyle rather than a rhizobial lifestyle.…”

Distribution and Diversity of Rhizobial Populations Associated with <i>Acacia senegal</i> (L.) Willd. Provenances in Senegalese Arid and Semiarid Regions

“…For each test, a control was performed, and inoculation and incubation were performed as described by Diouf et al (2010). The use of various carbohydrates (filter-sterilized, 0.2 µm) by rhizobial was tested on MGS agar plates according to the method described by Mohamed et al (2000).…”