Isolation and characterization of phosphate solubilizing rhizobia bacteria nodulating Vicia faba L. at the Haouz region of Morocco

Faba bean (Vicia faba L.) is one of the most important grain legumes grown in North Africa, thanks to its high protein content and ability to enhance soil fertility in rotation system or in intercropping. However, this crop is increasingly challenged by several abiotic stresses leading to severe yield loss. This study aims to isolate and characterize rhizobial strains nodulating faba bean with high phosphate solubilization potential. Rhizobia were isolated from root nodules of faba bean grown in the Haouz region. The results showed that from 50 isolates, only 22% and 16.6% of the total rhizobia isolates were able to solubilize tricalcium phosphate (TCP) on NBRIP and Sperber media respectively. Fb7a and Fb38 isolates presented high solubilizing index (SI) of 8.33 and 3.55 respectively. Indeed, Fb38, and Fb3b released the highest soluble phosphorus (Pi) concentrations of 1176.5 and 966.4 mg L^-1 respectively after 96h of incubation in Sperber broth. Meanwhile, Fb7b and Fb38 presented the highest acid phosphatase (APase) activities of 3.47 and 3.21 μmol pNP min^-1mL^-1 respectively in the presence of TCP as sole P source. Taking all together, with P solubilization and N_2-fixing abilities, the rhizobia inoculation may ensure biological nitrogen and phosphate nutrition to faba bean plants as well as for associated species in intercropping system or crop rotation.