Effects of bacterial and fungal endophytes on the growth of the model plants Medicago sativa and Arabidopsis thaliana under salt stress

Abstract

This study investigates the role of endophytic microorganisms, two bacterial strains (M17 and M67.2) and two fungal strains (KM405 and DA413) from Algerian soil, in improving salt stress tolerance in Medicago sativa and Arabidopsis thaliana. Under non-saline conditions, microbial inoculation sometimes reduced root growth, likely due to early competition or the activation of plant defense responses. However, under high salinity, the tested microorganisms significantly enhanced plant growth and stress tolerance. In Medicago sativa, bacterial strains M17 and M67.2 mitigated the inhibitory effects of 150 mM NaCl, suggesting the activation of salt-tolerance mechanisms such as ion homeostasis, phytohormone synthesis, and Osmo protectant accumulation. In Arabidopsis thaliana, fungal strains DA413 and KM405 substantially improved root development, leaf number, and lateral root formation under 100 mM NaCl, demonstrating their ability to enhance plant performance under severe stress. Overall, the results highlight the promising potential of endophytic bacteria and fungi as sustainable biological agents capable of enhancing plant resilience to salinity, providing an eco-friendly alternative for agriculture in salt-affected regions.