Arbuscular mycorrhizal fungi associated with endemic Moroccan lavender (Lavandula maroccana Murb.): effects on plant growth, volatile oil composition and antimicrobial activity

The increasing demand for Moroccan Lavender (Lavandula maroccana) accompanied by the drastic decline of its wild populations, requires a sustainable exploitation of this vulnerable Moroccan endemic medicinal plant. The aim of this study was to assess the effect of cultivation and the application of arbuscular mycorrhizal fungi (AMF) on the plant growth, chemical profile and the antimicrobial properties of volatile oil of L. maroccana. The results revealed that the inoculated plants achieved the highest biomass production. GC/MS investigation identified 48 compounds, representing 97.73% - 97.85% of the total essential oils (EOs), with carvacrol (44.58% - 55.12%), p-cymen-8-ol (4.84% - 6.41%), & alpha;-farnesene (4.11% - 4.74%) and 2-methoxy-4-vinylphenol (3.71% - 5.35%) as major constituents. From the comparative chemical compositions of cultivated and wild lavender EOs, it appears that cultivation induced a decrease in the carvacrol and p-cymen-8-ol contents, and inversely an accumulation of 2-methoxy-4-vinylphenol. The application of AMF led to an increase in carvacrol and p-cymen-8-ol levels compared to the untreated plants. The antimicrobial assays showed that EOs obtained from wild and cultivated plants exhibited interesting inhibitory effects against all tested strains (MICs from 0.30 to 5.00 mg/mL), with the oil from AMF inoculated plants being more active against some strains. Based on the outcome of the present investigation, cultivation using AMF inoculation may represent a promising biological treatment to enhance both bioactivity and plant growth, and to ensure the rational utilization of this valuable medicinal plant.