SEED BIOPRIMING WITH OSMO-TOLERANT RHIZOBACTERIA ENHANCES THE TOLERANCE OF ALFALFA (MEDICAGO SATIVA L.)-RHIZOBIA SYMBIOSIS TO WATER DEFICIT

The present study aims to assess the beneficial effect of seed biopriming with osmo-tolerant rhizobacteria on alfalfa (Medicago sativa L.)-rhizobia symbiosis submitted to water deficit. The experiment was carried out under greenhouse conditions on six symbiotic combinations involving two Moroccan alfalfa populations Adis-Tata and Demnate2 and an American Moapa variety inoculated with RcRh09 and Ensifer meliloti (Rm1021) strains. Half of the plants of each symbiotic combination were submitted to water deficit consisting of 40% field capacity (FC) of substrate, while the other half were kept under optimal irrigation conditions (80% FC). After five weeks of water deficit, some agrophysiological and biochemical properties associated with water deficit tolerance in alfalfa were selected for further focus. Results showed that seed biopriming significantly increased plant growth and nodulation in all of the tested symbiotic combinations under water deficit in comparison to unprimed seeds. Physiologically, the biopriming significantly improved photosynthetic-related traits such as chlorophyll contents, the maximum quantum yield of PS II (F-v/F-m) and stomatal conductance. Also, the macronutrient concentrations (P and K), the relative water content and membrane integrity, reflected by low malonyldialdehyde and electrolyte leakage values, were found improved by the pre-germination treatment. Our findings confirmed that the biopriming was an effective treatment for improving alfalfa growth and nodulation under water deficit.