Arbuscular mycorrhizal fungi enhance growth, mineral nutrition, metabolic traits and essential oil bioactivity in Thymus satureioides Coss.

Thymus satureioides is a native plant of the Moroccan Atlas Mountains and is valued for its culinary, medicinal, and cosmetic uses. The increasing pressure on its populations and its vegetation calls for sustainable farming. Arbuscular mycorrhizal fungi (AMF) are among the beneficial microbes that promote growth, phytochemicals, and bioactive properties. The role and interactions of AMF have been studied in several medicinal plants, but their specific influence on T. satureioides , including its biochemical composition, oil profile, antioxidant, and antimicrobial activities, has largely been overlooked. This study investigated how AMF influence the biochemical composition, oil profile, antioxidant activity, and antimicrobial activity of T. satureioides . The results showed that mycorrhizal inoculation significantly improved the biochemical composition of T. satureioides . Protein (1.16 vs. 0.82 mg mL -1 ), carbohydrate (89.26 vs. 68.51 mg mL -1 ), and lipid (0.82 vs. 0.64 mg mL -1 ) contents were higher in mycorrhizal seedlings. Secondary metabolites were also enhanced, with polyphenols (85.75 vs. 67 GAE/g EO) and flavonoids (94.44 vs. 71.11 mg Rutin/g DW) showing marked increases. GC-MS analysis revealed enrichment of key bioactive compounds, including thymol, carvacrol, and rosmarinic acid. Essential oils from AMF-inoculated seedlings exhibited stronger antioxidant activity and greater antimicrobial efficacy, with larger inhibition zones against all tested strains. The enhancement of primary and secondary metabolites in AMF-inoculated plantlets suggests that AMF symbiosis improves nutrient uptake and metabolic pathways involved in the biosynthesis of bioactive compounds. The increased levels of phenolic compounds and terpenoids explain the higher antioxidant and antimicrobial activities observed in the EOs. These findings demonstrate that AMF inoculation can act as an effective biostimulant, enhancing the plant nutritional and bioactive properties of thyme. Mycorrhizal inoculation boosts growth, mineral nutrition, biochemical profile, essential oils, and biological activities of T. satureioides . This eco-friendly mycorrhizal approach may contribute to the sustainable cultivation and valorization of Thymus satureioides , a North African endemic species, while promoting the production of high-value phytoproducts and supporting the conservation of its natural genetic resources.