Role of Rhizophagus intraradices in Mitigating Salt Stress of Sulla carnosa Through Modulating Plant Hormones (ABA, SA, and JA) and Nutrient Profile

Salt accumulation can degrade soil properties, decrease its productivity, and harm its ecological functions. Introducing salt-tolerant plant species associated with arbuscular mycorrhizal fungi (AMF) can act as an effective biological method for restoring salinized soils. AMF colonize plant roots and improve their nutrient acquisition capacity. However, there is limited knowledge on how AMF affects the production of signaling molecules, e.g., abscisic acid (ABA), salicylic acid (SA), and jasmonic acid (JA), related to plant-microbe interactions under salinity. Here, we assess the potential benefits of the AMF <i>Rhizophagus intraradices</i> in enhancing plant growth and nutrient uptake in addition to modulating stress hormone signaling levels (ABA, SA, and JA) of the facultative halophyte <i>Sulla carnosa</i> under saline conditions. Plants were grown in pots filled with soil and irrigated with 200 mM NaCl for 1 month. AMF symbiosis substantially increased the shoot dry weight (+107%), root dry weight (+67%), photosynthetic pigment content (chlorophyll a, chlorophyll b, and carotenoids), and nutrient uptake (C, N, P, K, Cu, and Zn) while significantly limiting the increase in the shoot Na⁺ concentration and H₂O₂ content caused by salinity stress. Mycorrhizal symbiosis significantly enhanced the root and shoot SA levels by 450% and 32%, respectively, compared to the stressed non-inoculated plants, potentially contributing to enhanced systemic resistance and osmotic adjustment under saline conditions. Salt stress increased the shoot ABA content, especially in <i>R. intraradices</i>-inoculated plants (113% higher than in stressed non-mycorrhizal plants). These findings confirm that AMF mitigated the adverse effects of salinity on <i>S. carnosa</i> by increasing the SA and ABA levels and reducing oxidative damage.