Effects of Arbuscular Mycorrhizal Fungi and Rhizobia Symbiosis on the Tolerance of Medicago Sativa to Salt Stress

Alfalfa is the most forage crop cultivated in Mediteranean area where salinity is one of the main limiting factors for its production. Thus, aconsortium of arbuscular mycorrhizal fungi (AM) isolated from the Aoufous palmeraie, Morocco, and autochthonous rhizobia strain (RhLO1) or their combination (AM+RhLO1) were tested for their efficiency to improve alfalfa tolerance to salinity. The grass waste compost was given as asource of organic matter to the soil. Antioxidant status, physiological parameters and growth of alfalfa were evaluated. The results showed that the highest alfalfa growth was reached in plants dually inoculated particularly under non-stress conditions. Dual inoculation also enhanced the stomatal conductance in control plants, while the nodule number and mycorrhizal infection were enhanced under both conditions. Salt stress did not affect the efficiency of photosystemII. However, single or dual inoculation increased this efficiency. RhLO1 or AM+RhLO1 symbiosis could alleviate the deleterious effects of salinity on alfalfa. They could maintain higher leaf water potential (LWP ), reducing the electrolyte leakages and malondialdehyde (MDA) content, inducing the accumulation of compatible osmolytes (sugar) and antioxidant enzymes as defense strategy. Thus, these autochthonous microorganisms were effective for alfalfa plants to alleviate salinity damage and improve plant growth and productivity.