Résumé
A total of fifty root nodules isolates of fast-growing and slow growing rhizobia from
Pterocarpus erinaceus and
Pterocarpus lucens respectively native of sudanean and sahelian regions of Senegal were characterized. These isolates were compared to representative strains of known rhizobial species. Twenty-two new isolates were slow growers and twenty-eight were fast growers. A polyphasic approach was performed including comparative total protein sodium dodecyl sulphate polyacrylamide gel (SDS-PAGE) profile analysis; 16S rDNA and 16S–23S rDNA intergenic spacer (IGS) sequence analysis. By SDS-PAGE the slow growing isolates grouped in one major cluster containing reference strains of
Bradyrhizobium sp. including strains isolated in Africa, in Brazil and in New Zealand. Most of the fast-growing rhizobia grouped in four different clusters or were separate strains related to
Rhizobium and
Mesorhizobium strains. The 16S rDNA and 16S–23S rDNA IGS sequences analysis showed accurately the differentiation of fast growing rhizobia among the
Rhizobium and
Mesorhizobium genospecies. The representative strains of slow growing rhizobia were identified as closely related to
Bradyrhizobium elkanii and
Bradyrhizobium japonicum. Based on 16S rDNA sequence analysis, one slow growing strain (ORS199) was phylogenetically related to
Bradyrhizobium sp.
(Lupinus) and
Blastobacter denitrificans. This position of ORS 199 was not confirmed by IGS sequence divergence. We found no clear relation between the diversity of strains, the host plants and the ecogeographical origins.