Genotypic characterization of Bradyrhizobium strains nodulating small Senegalese legumes by 16S-23S rRNA intergenic gene spacers and amplified fragment length polymorphism fingerprint analyses

We examined the genotypic diversity of 64 Bradyrhizobium strains isolated f rom nodules from 27 native leguminous plant species in Senegal (West Africa ) belonging to the genera Abrus, Alysicarpus, Bryaspis, Chamaecrista, Cassi a, Crotalaria, Desmodium, Eriosema, Indigofera, Moghania, Rhynchosia, Sesba nia, Tephrosia, and Zornia, which play an ecological role and have agronomi c potential in arid regions. The strains were characterized by intergenic s pacer (between 16S and 23S rRNA genes) PCR and restriction fragment length polymorphism (IGS PCR-RFLP) and amplified fragment length polymorphism (AFL P) fingerprinting analyses. Fifty-three reference strains of the different Bradyrhizobium species and described groups were included for comparison. T he strains were diverse and formed 27 groups by AFLP and 16 groups by IGS P CR-RFLP. The sizes of the IGS PCR products from the Bradyrhizobium strains that were studied varied from 780 to 1,038 bp and,cere correlated with the IGS PCR-RFLP results. The grouping of strains was consistent by the three m ethods AFLP, IGS PCR-RFLP, and previously reported 16S amplified ribosomal DNA restriction analysis. For investigating the whole genome, AFLP was the most discriminative technique, thus being of particular interest for future taxonomic studies in Bradyrhizobium, for which DNA is difficult to obtain in quantity and quality to perform extensive DNA:DNA hybridizations.