Trichoderma spp. are known as biocontrol agents of fungal plant pathogens and have been recognized as a potential source of bioactive metabolites. The production of antimicrobial substances from strains T. atroviride (TS) and T. asperellum (IMI 393899) was investigated. The bioactivity of 10- and 30-day culture filtrate extracted with ethyl acetate was assessed against a set of pathogenic fungi and oomycetes. The 30-day extracts of both strains had significant cytotoxic effects against the tested pathogens, with values of minimum fungicidal concentration (MFC) ranging between 0.19 and 6.25 mg/mL. Dual culture assay (direct contact and nondirect contact) and the percentage inhibition of radial growth (PIRG) was calculated. The highest PIRG values were 76% and 81% (direct contact) with IMI 393899 and TS, respectively. Nondirect contact does not show inhibition on any of pathogens tested, indicating that the inhibition is not due to the secretion of volatile substances. Culture filtrates were analyzed by GC-MS and HPLC-Q-TOF-MS for the identification of volatile organic compounds (VOCs) and nonvolatile organic compounds (nVOCs), respectively. Seven classes of VOCs and 12 molecules of nVOCs were identified. These results indicate that these strains of Trichoderma had antimicrobial activities and they are potential natural sources of compounds with biological activity.

Post-harvest fungal diseases of plant products are a serious concern leading to economic losses and health risks. Moreover, the use of synthetic chemical fungicides to prevent these diseases is limited due to toxic residues. This study aimed at determining the effective dose of extracts of Trichoderma asperellum IMI393899 (TE1) and Trichoderma atroviride TS (TE2) in inhibiting the contamination by mycotoxigenic fungi on different plant matrices. Extracts were tested on tomatoes contaminated by Fusarium verticillioides and Fusarium graminearum, wheat contaminated by Penicillium verrucosum and maize contaminated by Aspergillus flavus. The efficacy of extracts was evaluated at two time intervals after treatment, 4 and 11 days for tomato, and 10 and 20 days for both wheat and maize. Both extracts showed a significant inhibitory activity on mycotoxigenic pathogens and significantly reduced Log CFU/g compared to the control. Moreover, the extracts reduced mycotoxin production in a dose dependent manner and with a long-lasting effect. The ochratoxin A was reduced by both extracts but only the extract TE2 was effective in reducing aflatoxins, whereas TE1 treatment increased their synthesis.

In this study, the early activation of plant-defense-related genes during a three-way plant–antagonist–pathogen interaction in a tomato–Trichoderma–Phytophthora nicotianae model system was evaluated. Thirty-day-old tomato seedlings were treated at the root systems with a suspension of germinated conidia of two selected strains of T. asperellum and T. atroviride and then inoculated with zoospores of P. nicotianae. The defense mechanisms activated by tomato plants upon the simultaneous colonization of the root systems by Trichoderma spp. and P. nicotianae were evaluated 72 h post-inoculation by analyzing the transcriptomic profiles of genes involved in the pathways of salicylic acid (i.e., pathogenesis-related proteins—PR1b1 andPR-P2-encoding genes), jasmonic acid (i.e., lipoxygenases enzymes—TomLoxC- and TomLoxA-encoding genes), and the tomato plant defensin protein (i.e., SlyDF2-encoding gene). The results showed that PR1b1 was more strongly up-regulated in the three-way system including T. asperellum, while the gene PR-P2 was up-regulated in the system including T. atroviride. TomLoxA was significantly up-regulated only in the three-way system including T. asperellum, while TomLoxC was significantly up-regulated in neither of the analyzed three-way systems. Finally, the gene SlyDF2 was significantly up-regulated in tomato seedlings in both three-way systems.