Bioprotection of Cucumis melo from Alternaria leaf spot by Glomus mosseae and Trichoderma harzianum

Abstract

Alternaria alternata, responsible for Alternaria leaf spot, is spread worldwide, notably in Iraq. This disease is characterized by lesion formation on the leaves, leading to substantial yield and quality losses in several plant species such as Cucumis melo (melon). Glomus mosseae and Trichoderma harzianum are considered eco-friendly and bio-safe alternatives to traditional chemical fungicides due to their intrinsic ability to induce native anti-stress pathways in plants. This research study was conducted to evaluate the efficacy of the tested bio-agents, G. mosseae and T. harzianum (in combination or separately), on cucumber infected with A. alternata under greenhouse conditions. G. mosseae and T. harzianum provided strong inhibitory effects against leaf spot disease, decreasing disease severity index (DSI = 31.35 and 40.39%, respectively) and disease index (DI = 1.30 and 1.49, respectively). Obtained results revealed that the separate treatment of melon against this airborne pathogen using G. mosseae and T. harzianum generated the strongest activity of catalase (CAT = 5.678 and 3.389 units/mg protein/min, respectively) and peroxidase (POX = 9.948 and 7.542 units/g/ml/min, respectively). However, the ongoing results revealed that the combination of G. mosseae and T. harzianum negligibly reduced DSI (47.04%) and DI (2.08) and increased CAT (1.962 units/mg protein/min) and POX (3.08 units/g/ml/min) activities. To control A. alternata within integrated pest management strategies, biological control agents (such as G. mosseae and T. harzianum) should be considered.