Inhibitory Effect of Trichoderma citrinoviride Secondary Metabolites on the Growth Kinetics and Spore Germination of Fungal Phytopathogens

Hyphae fungi of the Trichoderma genus are widely recognized as effective biological control factors (BCAs) due to their ability to inhibit the growth of plant pathogens through a variety of mechanisms such as mycoparasitism, antibiotics or competition for resources. Specialized secondary metabolites (SMs), including volatile organic compounds (VOCs), lytic enzymes and surfactants, play an important role in these interactions. The aim of this study was to evaluate the antagonistic activity and characterization of secondary metabolites from the aqueous phase or suspended in an organic solvent produced by three strains of Trichoderma citrinoviride. The study focused on their enzymatic properties, surfactant potential and effect on the growth kinetics of sixteen fungal species. Antagonistic activity against phytopathogens was tested using the turbidimetric method, analyzing various forms of preparations. Lytic enzyme activity and surface tension of fluids were also evaluated. The C1 strain showed the broadest spectrum of antagonistic activity. Analysis of growth kinetics revealed that the way metabolites are prepared is crucial for their efficacy. Studies have shown that the effectiveness of biocontrol depends not only on the Trichoderma strain, but also on the extraction method and form of the preparation (e.g., rehydration of lyophilizate vs. organic phase extraction). The presence of diverse metabolites, including lytic enzymes, biosurfactants and volatile organic compounds, indicates a complex mechanism of action of T. citrinoviride, making this species an ideal candidate for the production of plant protection biopreparations.