In conclusion, mycoparasitism by T. harzianum was observed in all fungal structures of the ERM (i.e. in hyphae and spores), and for the first time, to our knowledge, within the IRM (i.e. in intraradical hyphae and vesicles) of the AM fungus Glomus sp. MUCL 41833. This observation sets up the debate on the susceptibility of AM fungi of being infected by microorganisms (i.e. pathogens or biological control agents) from the rhizosphere and to act as a channel for root penetration. Further studies must be performed to evaluate the impact T. harzianum on the growth, functionality and survival of the AM fungus and to assess the influence of the dual inoculation on plant performance.