Isolation and selection of autochthonous strains of Trichoderma spp. with inhibitory activity against Sporisorium reilianum

Head smut is a worldwide disease caused by the fungus Sporisorium reilianum. In Mexico, this phytosanitary problem has been described in the central part of the country, specifically in the Mezquital Valley in the state of Hidalgo, where this basidiomycete causes significant economic losses. In this work, seven strains of Trichoderma spp. were isolated from corn rhizospheres collected from crops in the affected zone. The isolates were identified as Trichoderma asperellum MH1, T. asperellum T4H1, T. harzianum T1H1, T. harzianum T1H3, T. atrobrunneum T1H2, T. tomentosum T2H4, and T. brevicompactum T3H1. All strains showed the ability to grow on the phytopathogen but with distinct degrees of mycoparasitism. SEM observations demonstrated the ability of T. asperellum T4H1 to invade the S. reilianum yeast growth. All the strains produced volatile compounds with antifungal activity. With the exception of T. asperellum MH1, all strains inhibited the development of the pathogen by means of non-volatile compounds. Production of the extracellular enzymes (lipase, cellulase, chitinase, protease, and laccase) was evaluated, with most strains presenting high lipolytic activity and low proteolytic activity. The production of cellulase and chitinase was observed only in five strains. Laccase production was found in three isolates. Evaluations at the greenhouse of the sequential application of three mixtures of the isolates were conducted in a greenhouse; findings showed that the phytopathogen was not detected by specific PCR in the plants that received the treatment.