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A Polyphasic characterization of 30 bacteria isolated from root nodules of Medicago arborea (Medic tree) plants growing in 3 arid soils of the arid northeast region of Morocco was performed. The phenotypic, symbiotic, and cultural characteristics analyzed allowed the description of a broad physiological diversity among the isolates. The phenogram obtained showed 3 main clusters at a similarity coefficient of 78%. The results obtained suggest that the phenotype of these rhizobia might have evolved for adaptation to the local conditions.

The genetic characterization which consisted in a rep PCR using ERIC (Enterobacterial Repetitive Intergenic Consensus) primers showed a great diversity and 3 groups and 8 clusters were delimited at a similarity level of 80%. However, the 16S rDNA sequences showed a perfect identity of all the isolates with Sinorbizobium meliloti published sequences.

The results showed a relationship between rep-PCR fingerprinting and phenotypic techniques, which are complementary in diversity investigation and allowed revelation of relationships between M. arborea close-related bacterial isolates originated from different geographic location in the northeast area of Morocco.