In vitro assessment of the biocontrol activities of some Trichoderma species in suppressing Fusarium oxysporum f. sp. lycopersici

Tomato Fusarium wilt is one of the crucial diseases threatening tomato production worldwide. In this study, the in vitro antagonistic potential of four Trichoderma species (Trichoderma koningii K-19, T. harzianum K-20, T. brevicompactum K-26, and T. atroviride TR-1) was evaluated using dual culture assays, volatile organic compound (VOC) bioassays, and cell-free culture filtrate (CFCF) tests. All tested isolates significantly inhibited pathogen mycelial growth in different bioassays. Among them, T. koningii K-19 consistently exhibited the strongest antagonistic activity, achieving inhibition rates of 70.37% in dual culture assays, 45.48% in sealed plate assays, and 43.10% in culture filtrate assays. In comparison, T. harzianum K-20, T. atroviride TR-1, and T. brevicompactum K-26 inhibited pathogen growth by 65.31%, 60.68%, and 66.40% in dual culture assays; 24.29%, 32.38%, and 31.43% in sealed plate assays; and 34.52%, 28.81%, and 35.95% in culture filtrate assays, respectively. These findings indicate that T. koningii K-19 suppresses the Fusarium wilt pathogen through multiple antagonistic mechanisms, such as competition, antibiosis, and volatile antifungal compounds. These findings demonstrate the potential of T. koningii K-19 as a promising biocontrol agent against tomato Fusarium wilt, requiring evaluation of its effectiveness in field trials in further studies.