Phenotypic and Genotypic Diversity of Microsymbionts Nodulating Medicago sativa (L.) in the Algerian Sahara

Abstract

This work was conducted to evaluate the phenotypic and phylogenetic diversity of 48 rhizobial strains. All rhizobial strains exhibited a broad tolerance to salinity and pH. In general, they grew well at 28°C and 37°C but poorly at 4°C and 45°C. The rhizobial strains showed an array of antibiotic sensitivity patterns. The numerical (UPGMA) analysis of phenotypic traits and the phylogenetic tree of concatenated housekeeping genes produced highly similar results. Phylogenetic analysis of recA and glnII showed that all the isolates were affiliated to the genus Sinorhizobium, but belong to two distinct groups: Group I, originating in Ghardaïa, was close to the species S. meliloti and S. kummerowiae. Group II, originating in Ouargla and El Oued, clustered separately from sequences of known Sinorhizobium species, which suggests they could be a new lineage. The classifications resulting from the nodC gene reflect host specificity, while phylogeny based on chromosomal genes is independent of the host plant. Based on the studies documented in the literature, the genetically characterized rhizobial strains can be used as an effective inoculant for the improvement of forage yields in Saharan regions.