GENETIC AND PHENETIC ANALYSES OF BRADYRHIZOBIUM STRAINS NODULATING PEANUT (ARACHIS-HYPOGAEA L) ROOTS

Seventeen Bradyrhizobium sp. strains and one Azorhizobium strain were compared on the basis of five genetic and phenetic features: (i) parti al sequence analyses of the 16S rRNA gene (rDNA), (ii) randomly amplif ied DNA polymorphisms (RAPD) using three oligonucleotide primers, (iii ) total cellular protein profiles, (iv) utilization of 21 aliphatic an d 22 aromatic substrates, and (v) intrinsic resistances to seven antib iotics. Partial 16S rDNA analysis revealed the presence of only two rD NA homology (i.e., identity) groups among the 17 Bradyrhizobium strain s. The partial 16S rDNA sequences of Bradyrhizobium sp. Strains form a tight similarity (>95%) cluster with Rhodopseudomonas palustris. Nitr obacter species, Afipia species, and Blastabacter denitrificans but we re less similar to other members of the alpha-Proteobacteria, includin g other members of the Rhizobiaceae family. Clustering the Bradyrhizob ium sp. strains for their RAPD profiles, protein profiles, and substra te utilization data revealed more diversity than rDNA analysis. Intrin sic antibiotic resistance yielded strain-specific patterns that could not be clustered. High rDNA similarity appeared to be a prerequisite, but it did not necessarily lead to high similarity values between RAPD profiles, protein profiles, and substrate utilization. The various re lationship structures, coming forth from each of the studied features, had low compatibilities, casting doubt on the usefulness of a polypha sic approach in rhizobial taxonomy.