Ononis repens is a legume of the Fabaceae family with great ecological and medicinal importance that grows wild in the Maamora cork oak forest (Rabat, Morocco). The aim of this work was to analyze the diversity, phylogeny, and plant growth-promoting features of the plant root nodules microsymbionts. Out of twenty nodC-containing rhizobial bacteria, four strains, ORM6, ORM8.1, ORM 13.1, and ORM16, were selected for further molecular and phenotypic analyses. All four strains were able to metabolize a wide range of carbohydrates and amino acids as sole carbon and nitrogen sources, respectively, and grew in the presence of different pH, NaCl, and temperature conditions. They also solubilized inorganic phosphate and produced siderophores, and ORM16 was the only strain to produce indol acetic acid. The rrs gene sequence analysis showed that the four strains are members of the Mesorhizobium genus. The individual and concatenated sequences of the recA, glnII, and gyrB housekeeping genes revealed that the strains ORM6 and ORM 13.1 clustered with M. jarvisii ATCC 33,669 and M. intechii BD68 , with which they share 93.3 and 93.7% similarity, respectively; that the strain ORM8.1 affiliated with a group of which the strain M. shonense AC39a was the closest relative species with 84.3% similarity; and that the strain ORM16 clustered with M. australicum LMG24608, with 80.5% similarity. These results suggest that the four O. repens-isolated strains could belong to three putative new genospecies. All four strains nodulated their original host as well as Astragalus gombiformis and A. armatus, but only the strain ORM16 was able to form nodules on Vachellia gummifera. Analysis of the symbiotic nodC gene phylogenies showed that the strains ORM6, ORM8.1, ORM 13.1, and ORM16 formed a group apart from the known symbiovars in the genus Mesorhizobium, for which the name maamori is proposed.

This work was supported by Hassan II Academy of Sciences and Technology, in Morocco. Grant P18-RT-1401 from Junta de Andalucía is also acknowledged. The authors want to thank all the persons who contributed to this work.