Plant growth-promoting rhizobacteria isolated from argan tree soil inducing systemic drought tolerance in alfalfa

The occurrence of climate change has resulted in extremely dry climatic conditions, which led to a significant impact on crop growth and productivity. The rhizosphere of the endemic argan forest could be a baring ground for naturally unexplored plant growth-promoting rhizobacteria (PGPR). A greenhouse experiment was conducted to evaluate the effect on alfalfa plants under drought conditions of four selected rhizobacteria, including two actinobacteria, in combination with two naturally endosymbiont Ensifer meliloti strains (RhOL). A completely randomized design was used with water stress as the main factor consisting of two regimes: (1) well-watered plants (75% field capacity (FC)) and (2) water-stressed plants (35% FC), and PGPR inoculation as a second factor consisting of four inoculation treatments: control, consortia (LBA8 + LBA19 + RhOL6 + RhOL8 strains), (3) consortia 2 (LB4 + LBP2 + RhOL6 + RhOL8 strains), and (4) consortia 3 (LBA8 + LBA19 + LB4 + LBP2 + RhOL6 + RhOL8 strains). Inoculated alfalfa plants showed tolerance to drought stress by increased production of total chlorophyll and osmolytes, including proteins and sugars, under drought stress. The bacterial inoculation led to a lower H 2 O 2 content in alfalfa leaves and neutralized the reactive oxygen species. These PGPR strains appeared to be important tools capable of being developed into bioinoculants to effectively improve drought tolerance in plants in a sustainable agriculture strategy.