Arbuscular mycorrhizal fungi (AMF) improve resistance to both biotic and abiotic stresses of the host plants. Viruses are one of the most important plant pathogens. Currently, there are no curative measures for managing plant virus infections and all the actions are limited to preventive strategies. Therefore, harnessing symbiotic microbes could enhance plant resistance to these pathogens. The effects of mycorrhizal symbiosis on viral infections are contradictory. Some mycorrhizae-plant interactions lead to resistance while others give rise to sensitivity of the host plant. In this study, interaction between tomato plant, an AMF (Glomus fasciculatum, GF) and Tomato mosaic virus (ToMV) was investigated to test the ability of the GF in conferring resistance to the tomato plants in ToMV infection. Various plant phenotypic and biochemical traits were analyzed by factorial completely randomized design in three repetitions. All treatments were compared to the plants infected only by ToMV as control. Visual assessment of the virus symptoms and disease severity indexing (DSI) showed that GF delayed the development of disease symptoms for two days and disease severity reduced (-10%). Plant height (+26%) and its wet (+40%) and dry (+45%) weights of aerial parts increased significantly. Besides, GF caused significant increases in leaf contents of N (+210%), K (+75%), chlorophyll a (+89%), Chlorophyll b (+133%) and carotenoid (+53%) in virus-infected plants. Total phenolic content (+ 116%), ascorbate peroxidase (+43%) and catalase (+33%) activities were improved significantly. All together, these findings imply that GF confers resistance in tomato plants against ToMV infection.
