Biocontrol of Fusarium spp. root rot in yerba mate (Ilex paraguariensis) by native rhizospheric Trichoderma spp.

Yerba mate (Ilex paraguariensis) is a native plant from South America where its leaves and branches are popularly consumed in warm drinks. Species of Fusarium may attack the plant and cause root rot. Biological control using native fungi may support the yerba mate protection against root rots. This work aimed to identify and characterize Trichoderma isolates able to control Fusarium oxysporum and Fusarium solani and promote growth in I. paraguariensis. Fungi of the genus Trichoderma were isolated from the rhizosphere of I. paraguariensis and identified molecularly using the ITS, TEF-1α and RPB2 regions. The in vitro antagonistic activity of Trichoderma isolates was evaluated by direct confrontation and production of volatile compounds against the Fusarium spp. In planta experiments were conducted in a greenhouse, where Trichoderma isolates were incorporated into substrate at different times in relation to the Fusarium spp. inoculation. Seven isolates were identified as T. asperelloides, T. hamatum and T. koningiopsis. All Trichoderma isolates reduced up to 30.17% the mycelial growth of the pathogens in the confrontation test. Also, the volatile emission reduced significantly the Fusarium spp. mycelial growth. In the greenhouse, isolates T. koningiopsis IMDI, T. asperelloides ACI and T. asperelloides AVRIII reduced rot symptoms and promoted seedling growth. Biochemical analyses demonstrated that Trichoderma isolates increased oxidative enzymes in the plants. Therefore, native isolates of T. asperelloides and T. koningiopsis antagonized and controlled root rot pathogens and promoted I. paraguariensis growth, demonstrating potential to be used in yerba mate protection.