Symbiotic, phenotypic and genotypic characterization of Bradyrhizobium sp. nodulating Spartium junceum L. from Bejaia, northeastern Algeria

Abstract

Twenty-three bacterial strains were isolated from root nodules of Spartium junceum L., growing wild in four distinct geographic locations in Bejaia city (Northeastern Algeria). They were analyzed based on their symbiotic effectiveness, phenotypic properties and restriction fragment length polymorphism of the 16S rRNA gene. In addition, sequence analyses of the ribosomal gene, protein-coding housekeeping genes glnII and recA, and symbiotic gene (nodC) were used to clarifying their taxonomic and phylogenetic position. Plant infection tests revealed that all strains were able to form nodules on their original host plant, but with variable nodulation ability and symbiotic effectiveness. All strains were slow-growing, alkali-producing rhizobia in YEMA medium. According to phenotypic test results, the strains were grouped in four main clusters in a UPGMA dendrogram, while they were discriminated into 12 distinct genotypes by 16S rDNA-RFLP. Phylogenetic analyses of 16S rRNA genes and two concatenated housekeeping genes, glnII and recA, distributed the representative strains from each RFLP genotypes into two major clades within Bradyrhizobium genus. Some of these strains were closely related to B. retamae and B. japonicum whereas others represented four novel genospecies. Based on analysis of the symbiotic gene sequence (nodC), all strains were placed in the symbiovar retamae cluster except for SjBA12 which possibly constitutes a new symbiovar within the genus Bradyrhizobium.