Genotypic diversity of rhizobia isolated fromRetama raetam in arid regions of Tunisia

Thirty-five isolates of rhizobia were picked up fromRetama raetam root nodules growing in arid lands of Tunisia. A genotypic approach including PCR-RFLP of 16S rDNA and 16S–23S rDNA was used to study their diversity and their relationships with te n reference strains of rhizobia. Four distinct clusters were defined in numerical analysis of RFLP of 16S rDNA, which related at the 78% similarity level to distinct species ofMesorhizobium, Agrobacterium, Rhizobium andSinorhizobium. More greater variability was detected by analysis of Intergenic Spacers 16S–23S rDNA. The results from both methods used in this study, showed that among all newsolates only three were found to be closely related to species of the genusSinorhizobium.