Genetic diversity and phylogeny of rhizobia that nodulate Acacia spp. in Morocco assessed by analysis of rRNA genes

Forty rhizobia nodulating four Acacia species (A, gummifera, A. raddiana, A . cyanophylla, and A, horrida) were isolated from different sites in Morocc o, These rhizobia mere compared by analyzing both the 16S rRNA gene (rDNA) and the 16S-23S rRNA spacer by PCR with restriction fragment length polymor phism (RFLP) analysis, Analysis of the length of 16S-23S spacer showed a co nsiderable diversity within these microsymbionts, but RFLP analysis of the amplified spacer revealed no additional heterogeneity. Three clusters were identified when 16S rDNA analysis was tarried out. Two of these clusters in clude some isolates which nodulate, nonspecifically, the four Acacia specie s, These clusters, A and B, fit within the Sinorhizobium lineage and are cl osely related to S, meliloti and S. fredii, respectively. The third cluster appeared to belong to the Agrobacterium-Rhizobium galegae phylum and is mo re closely related to the Agrobacterium tumefaciens species, These relation s were confirmed by sequencing a representative strain from each cluster.