F. Zakerian - Department of Horticultural Science and Agronomy, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.
F. Sefidkon - Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Islamic Republic of Iran.
B. Abbaszadeh - Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, Islamic Republic of Iran.
S. Kalate Jari - Department of Horticultural Science and Agronomy, Science and Research Branch, Islamic Azad University, Tehran, Islamic Republic of Iran.

Satureja sahendica Bornm is an endemic, native, and aromatic plant in Iran, with thymol being its main and major volatile component, which is used in food and pharmaceutical industries. Increasing the oil yield and phenolic compounds in essential oil leads to increased medicinal effects. In this study, the effects of mycorrhizal fungi (Glomus mosseae, G. intraradices, and combination of G. mosseae and G. intraradices) and different levels of water stress [D۱= Control (no water stress), D۲= No irrigation during stem elongation till blooming, D۳= No irrigation at the blooming up to start of flowering, and D۴= No irrigation at ۵۰% flowering up to full flowering] were studied on S. sahendica oil, in two years. When the seedlings were transferred to the field, ۱۰ g of mycorrhiza fertilizer (containing mycorrhizal fungus spores) were added to the rhizosphere of each seedling. The plants were harvested at full flowering and the essential oils were obtained by hydro-distillation and analyzed by GC and GC/MS. The highest amount of oil yield (۶۶.۱۳ kg ha-۱) was obtained using G. intraradices in non-stress conditions in the second year. The highest percentage of thymol was obtained in G. mosseae×control in the first year (۷۴.۵۹%), whereas in the second year, the highest amount of thymol was in G. mosseae×D۴ (۶۱.۹۷%). This study showed that with the use of mycorrhizal fungi, even in conditions of water shortage, S. sahendica produced more essential oil with a higher percentage of thymol. With the use of mycorrhizal fungi, the essential oil can easily be increased and the number of compounds changes.

G. intraradices, Glomus mosseae, Inoculation, Medicinal plants, Thymol.