Arbuscular mycorrhizal fungi alleviate salinity stress and alter phenolic compounds of Moldavian balm

Mycorrhizal fungi are known to modulate the destructive effects of environmental stresses on plants. Arbuscular mycorrhizal fungi (AMF) symbiosis increases growth and stimulates the biosynthesis of bioactive compounds, thereby influencing polyphenolics content in medicinal plants under salt stress. The present study investigated the effects of AMF on growth traits, cell death, non-enzymatic antioxidants, and changes in the profile of phenolic compounds of Dracocephalum moldavica L. by HPLC analysis under different salinity concentrations. The experiment was performed as a factorial experiment based on a randomized complete block design including salinity treatment at four levels (0, 50, 100, and 150 mM NaCl) and mycorrhizal fungus treatment at three levels including non-inoculation and inoculated with Funneliformis mosseae and Claroideoglomus etunicatum with three replications. The experiment was performed in sterile controlled conditions in laboratory. The results showed that salinity reduced root colonization compared to the control conditions. Inoculation with AMF increased growth parameters and salinity tolerance of Deracocephalum Moldavica under all salinity levels. Through highperformance liquid chromatography, nine phenolic acids and flavonoids were analyzed in all treatments. Salinity and AMF inoculation altered the polyphenol profiles of Moldavian balm. F. mosseae inoculation increased most of the polyphenols at 50 and 150 mM NaCl, and C. etunicatum inoculation increased polyphenols at 100 mM NaCl more than F. mosseae. suggesting that F. mosseae and C. etunicatum mitigated the adverse effects of salinity, triggering non-enzymatic antioxidant activity by the accumulation of the flavonoid in roots and shoots and phenol in roots, enhancing growth parameters and reducing root cell death compared to non-mycorrhizal plants. As a positive point, salinity and mycorrhizal inoculation influenced the polyphenol content of D. moldavica and improved the production of phenolic compounds.