University of Tehran International Journal of Horticultural Science and Technology 2322-1461 13 4 2026 10 01 Enhancement of Growth and Essential Oil Traits of Spearmint and Peppermint through Mycorrhizal and Trichoderma Inoculations 789 802 104635 10.22059/ijhst.2025.390047.1024 EN Sima Hosein-Zade Department of Horticultural Science, Tarbiat Modares University, Tehran, Iran. Mohammad-Taghi Ebadi Department of Horticultural Science, Tarbiat Modares University, Tehran, Iran. Mahdi Ayyari Department of Horticultural Science, Tarbiat Modares University, Tehran, Iran. Journal Article 2025 02 06 This study evaluated the effects of arbuscular mycorrhizal fungi (AMF) and Trichoderma harzianum on growth, essential oil (EO) yield, and physiological traits in two spearmints (Mentha spicata) and one peppermint (Mentha × piperita) landrace. AMF treatments included Glomus etunicatum and Glomus fasciculatum, while T. harzianum was also tested. Combined inoculations significantly enhanced plant height, EO yield, and phytochemical composition. Spearmint plants treated with G. fasciculatum + T. harzianum reached the tallest height, and EO yields peaked at 2.8% in spearmint (Qaemshahr landrace) and 2.6% in spearmint (Vardavard landrace) under similar treatment. Limonene content in spearmint reached 20% with G. fasciculatum, while carvone peaked at 54% with G. etunicatum + T. harzianum. In peppermint, menthol content was highest (40.25%) with T. harzianum alone, and L-menthone peaked (34.9%) under G. fasciculatum + T. harzianum. Photosynthesis rates, stomatal conductance, and transpiration rates were highest in peppermint treated with G. fasciculatum + T. harzianum during the second harvest. Additionally, the greenness index peaked in peppermint treated with T. harzianum alone. These findings demonstrate the synergistic potential of AMF and T. harzianum in improving growth, physiological traits, and EO production in mint species, offering a promising strategy to enhance commercial mint cultivation. https://ijhst.ut.ac.ir/article_104635_bcb086544afcca07584a131b93f6fe18.pdf