Diversity of rhizobia nodulating Crotalaria spp. from Senegal

A total of 117 rhizobia strains was isolated from root nodules of nine Crot alaria spp. Nodules were collected at eight geographical sites in Senegal. Growth in yeast mannitol agar (YMA) revealed that rhizobia strains of Crota laria spp. include both fast and slow-growing strains. Host-specificity sho ws two groups of specificity in Crotalaria spp. tested: group I includes C. glaucoides, C. perrottetii and C. podocarpa which were effectively nodulat ed only by fast-growing strains, and group II includes C. comosa, C. goreen sis, C. hyssopifolia,C. lathyroides,C. ochroleuca,C. retusa which were effe ctively nodulated only by slow-growing strains. Slow-growing rhizobia have a broad host range and nodulated Crotalaria of group II and Acacia albida a nd Indigofera microcarpa, while fast-growing strains nodulated only Crotala ria spp. None of the strains effectively nodulated Sesbania rostrata or Aca cia raddiana. Numerical analysis of whole cells proteins profiles of these strains obtained by SDS-PAGE shows that slow-growing strains are related to Bradyrhizobium japonicum and fast-growing strains are not related to any k nown reference strains and constituted a new group of rhizobia.