Effects of mycorrhizal fungal symbiosis on the growth and chemical composition of the food preservative Salvia officinalis

Arbuscular mycorrhizal fungi (AMF) develop symbiotic relationships with plant roots, where they improve important physiological functions like growth, photosynthesis, and the production of bioactive substances. To study the effect of mycorrhizal fungal symbiosis, Salvia plants were grown with or without Rhizophagus irregularis inoculation, and shoots, roots, and rhizosphere soil were collected for biomass and biochemical analyses. AMF inoculation led to substantial improvements in Salvia officinalis with significant increases in growth (48.8%), photosynthetic efficiency (42.6%), and essential oil yield (63.2%) compared to non-inoculated plants. The improved photosynthetic activity under AMF treatment resulted in elevated carbohydrate production, particularly soluble sugars. The enhanced accumulation of amino acids - especially phenylalanine - supports the synthesis of secondary metabolites since phenylalanine acts as a key precursor for phenolic compounds and flavonoids via the phenylpropanoid pathway. AMF-treated plants exhibited marked increases in both primary metabolites (e.g., amino acids, soluble sugars, organic acids) and secondary metabolites (e.g., phenolics, flavonoids, alkaloids, glycosides), indicating a favorable shift in carbon allocation toward bioactive compound production. Flavonoid content rose by 21.7%, while phenolic compounds and essential oils also showed significant qualitative and quantitative enhancements. Furthermore, antioxidant capacity increased notably, as indicated by a 34.4% rise in ferric reducing antioxidant power (FRAP) values. The AMF-inoculated plants also demonstrated enhanced antibacterial and anticarcinogenic properties, underlining the role of AMF in stimulating the production of defense-related secondary metabolites. Overall, AMF inoculation significantly increased Salvia officinalis growth, metabolic activity, and synthesis of bioactive compounds, proving its efficacy as a natural method to increase the agronomic value and functional quality of this food preservative plant.