Characterization of plant growth-promoting mechanisms of rhizobacteria from the rhizosphere of date palms in tafilalet oases

Tafilalet is the largest oases in Morocco, but it is threatened by climatic and environmental stress like drought, soil degradation as well as plant diseases, in particular Fusarium wilt of date palm caused by Fusarium oxysporum f.sp albedinis (Foa). Soils are poor in terms of organic matter, nutrient concentrations and biological activity resulting in a dramatic decrease in date palm growth. Improving date palm productivity is regularly achieved by the excessive application of chemical fertilizers, which are harmful for human health and environment. In this work, we aimed at screening the plant growth-promoting rhizobacteria (PGPRs) and at the same time acting as biocontrol agents against Foa. Rhizobacteria associated with date palm and spontaneous plants in Tafilalet oases have been isolated and functionally characterized. Several plant growth promoting and biocontrol traits were investigated, including nutrients solubilization, and the production secondary metabolites and enzymes. Results showed that 97 % of strains was effective in N-fixation, 36 % in ammonia production, 90 % in P-solubilization. The Siderophores and Indol 3-acetic acid production were observed at 30 and 32 strains respectively. Besides, 78 % of strains had an inhibitory effect against Foa, in which 42 % completely inhibited the mycelia growth on PDA medium. Several strains produced cellulase, protease, amylase, chitinase and other secondary metabolites like hydrogen cyanide. Based on these results, consortia of efficient PGPRs could be selected and used as efficient microorganisms for future greenhouse and field experiments