Evaluation of Funneliformis Mosseae Inoculation Effects on Growth, Nutrient Uptake, and Essential Oil Content in Turkish Oregano Under Drought Stress

Abstract

Background. Turkish oregano (Origanum onites L.) is a perennial herb widely recognized for its medicinal, cosmetic, and culinary uses due to its antioxidant and antimicrobial properties. Drought is a significant stressor for crops, particularly affecting O. onites quality and yield. Arbuscular mycorrhizal fungi (AMF) establish symbiotic relationships with plant roots, enhance plant growth, and improve tolerance to abiotic stresses such as drought. Methods. This study investigates the effects of Funneliformis mosseae inoculation on O. onites growth, nutrient content, and essential oil yield under varying drought conditions. A factorial experiment was conducted with eight treatments, consisting of two factors: irrigation levels (100%, 75%, 50%, and 25%) and AMF inoculation (with and without). The experimental design was completely randomized with three replicates. Results. Results demonstrated that AMF inoculation significantly improved the fresh and dry weight of O. onites compared to non-inoculated controls (+11% and +16%, respectively). Moreover, AMF-inoculated plants showed notable increases in potassium (+7%) and nitrogen (+12%) contents. The essential oil yield was also significantly higher in AMF-inoculated plants (+3%). Increasing water stress levels significantly decreased the number of AMF spores (-47%) and the percentage of fungal colonization (-57%). Nevertheless, under drought stress mycorrhizal inoculation significantly maintained plant biomass and nutrient uptake comparable to full irrigation. The AMF drought tolerance effects were confirmed at 75%, 50%, and 25% irrigation rates.