Millions tons of lead and zinc wastes from the abandoned Touissit mine are stored in the open air as dikes in the vicinity of the villages in Eastern Morocco and pose a real danger to both the environment and local populations. To prevent the movement of minerals to the nearby villages and limit the damages to the environment and health, we proposed the nitrogen-fixing leguminous shrub Retama monosperma , as a model plant to use for phytostabilization experimentations. This plant species is known by its ability to grow in hard climatic conditions and in heavy metals contaminated soils. The isolation of bacterial strains nodulating R. monosperma in the abandoned mine soils will permit the selection of rhizobia to inoculate young plant seedlings before their use for the phytostabilization of the mine tailings. In this work, 44 bacteria were isolated from the root nodules of R. Monosperma grown in the Touissit abandoned mine. Twenty-four isolates were considered as true rhizobia as they possess a copy of the nodC symbiotic gene and were able to renodulate their original host. The phenotypic characterization showed that all the strains are tolerant in vitro to different concentrations of heavy metals. The analysis of the 16S rRNA sequences of two selected representative strains showed they were related to different strains of Ensifer aridi isolated from different legumes in three continents deserts. The glnII , recA , and gyrB housekeeping genes analysis confirmed the affiliation of the strains to E. aridi . Moreover, the phylogenic analysis of nodA , nodC , and nifH symbiotic genes showed that the strains are more related to E. aridi JNVUTP6 species isolated from Tephrosia purpurea root nodules in the Thar Desert in India. To our knowledge, this is the first report about the isolation of E. aridi from R. monosperma root nodules.

Aim To analyse the diversity of nodule‐forming bacteria isolated from Lupinus cosentinii naturally grown in the Maamora cork oak forest (Rabat, Morocco). Methods and Results Of the 31 bacterial strains, four were selected based on their REP‐PCR fingerprinting that were studied by sequencing and phylogenetic analysis of their 16S rRNA, gyrB, dnaK, recA and rpoB housekeeping genes as well as the nodC symbiotic gene. The nearly complete 16S rRNA gene sequence of the four representative strains showed that they are related to Tunisian strains of genus Microvirga isolated from L. micranthus with nucleotide identity values ranging from 98·67 to 97·13%. The single and concatenated sequences of the 16S rRNA, gyrB, dnaK, recA and rpoB housekeeping genes indicated that the L. cosentinii‐isolated strains had 99·2–99·9% similarities with the Tunisian L. micranthus microsymbionts. The nodC gene phylogeny revealed that the Moroccan strains clustered in the newly described mediterranense symbiovar, and nodulation tests showed that they nodulated not only L. cosentinii but also L. angustifolius, L. luteus and L. albus. Conclusions To the best of our knowledge, this is the first report concerning the isolation, molecular identification and phylogenetic diversity of L. cosentinii nodule‐forming endosymbionts and of their description as members of the Microvirga genus. Significance and Impact of the Study In this work, we show that Microvirga sp. can be isolated from root nodules of wild‐grown L. cosentinii in Northeast Africa, that selected strains also nodulate L. angustifolius, L. luteus and L. albus, and that they belong to symbiovar mediterranense. In addition, our data support that the ability of Microvirga to nodulate lupines could be related to the soil pH, its geographical distribution being more widespread than expected.

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In this work, we analyzed the diversity of the nodule-forming bacteria associated with Lupinus luteus and Lupinus cosentinii grown in the Maamora Cork oak forest acidic soils in Morocco. The phenotypic analysis showed the high diversity of the strains nodulating the two lupine's species. The strains were not tolerant to acidity or high alkalinity. They do not tolerate salinity or high temperatures either. The strains isolated from L. luteus were more tolerant to antibiotics and salinity than those isolated from L. cosentinii. The plant growth promoting (PGP) activities of our strains are modest, as among the 28 tested isolates, only six produced auxins, six produced siderophores, whereas three solubilized phosphates. Only two strains possess the three activities. The rrs gene sequences from eight representative strains selected following ARDRA and REP-PCR results revealed that they were members of the genus Bradyrhizobium. Six strains were then retained for further molecular analysis. The glnII, recA, gyrB, dnaK, and rpoB housekeeping gene sequence phylogeny showed that some strains were close to B. lupini LMG28514T whereas others may constitute new genospecies in the genus Bradyrhizobium. The strains were unable to nodulate Glycine max and Phaseolus vulgaris and effectively nodulated L. luteus, L. cosentinii, L. angustifolius, Chamaecytisus albidus, and Retama monosperma. The nodC and nodA symbiotic gene phylogenies showed that the strains are members of the genistearum symbiovar.

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