Identification and evaluation of secondary metabolites by gas chromatography-mass spectrometry (GC-MS) in native strains of Trichoderma species

Trichoderma species is a heterotrophic saprobion organism, which competes with other microorganisms, preventing them from developing. This fungus has mechanisms of action, among which are: production of antibiotics and metabolites, and hyperparasitism, which also promotes the induction of systemic resistance in plants. In this study, five native Trichoderma strains which were collected from agricultural land in Tamaulipas, Mexico were evaluated. The objective of this research was to identify the secondary metabolites produced by native strains of Trichoderma spp. under in vitro conditions and evaluation of the effect of these compounds on the growth of the pathogen Fusarium oxysporum and the germination of tomato seeds (Solanum esculentum). The production of Trichoderma's metabolites was performed by culturing in 150 ml of potato broth supplemented with sucrose (5%) and yeast extract (5%). Inoculation was performed by the addition of a 4 mm disk of active mycelium and allowed to grow at 25C ± 2°C and 12 h light/dark on a rotary shaker at 150 rpm for three weeks. Subsequently, the extraction of metabolites was performed using liquid: liquid phase which consisted of the filtrate and methylene chloride in a ratio of 1:3, and then the organic phase was recovered. The organic fraction was evaporated at 40°C with the aid of a rotary evaporator (Buchi®); the sample was recovered in 1 ml of methylene chloride. Analysis by GC-MS indicates that Trichoderma isolates produced 41 secondary metabolites of volatile and semi-volatile molecules and was observed, such that the number of compounds varies from the species analyzed and the collection site. The evaluation of the antagonistic activity of the extracts of Trichoderma spp. on F. oxysporum showed no significant differences between treatments (P=0.05); however, it was observed that pigmentation decreased in the mycelium of the pathogen. Regarding the evaluation of the effect of the extracts on the seeds of tomato, it was observed that the compounds of Trichoderma asperellum (TV1) induced the germination and the development of the seedling.   Key words: Volatile compounds, Trichoderma, gas chromatography-mass spectrometry secondary metabolites, Solanum esculentum.