Trichoderma virens DM5 Against Agroathelia rolfsii in Tomato: A Gateway to Understanding Its Biocontrol–Biostimulant Trade-Off

Agroathelia rolfsii causes stem rot in multiple crops, survives as sclerotia in the absence of host plants, and remains a difficult-to-manage pathogen globally. Although Trichoderma species offer a sustainable biocontrol solution, their dual roles as antagonists and plant biostimulants present a complex trade-off under stress conditions that remains underexplored. This study analyzed the pathogen suppression and plant growth promotion induced by Trichoderma virens DM5 in the context of tomato protection against A. rolfsii. Using a combination of phenotypic assays and transcriptomic analyses, we observed that T. virens DM5 suppressed A. rolfsii via both mycoparasitism and antibiosis, producing antifungal compounds that inhibited pathogen growth. Simultaneously, it enhanced host vigor by increasing seed germination by 54.5% and plant survival rates by 70% under pathogen pressure. Molecular analyses revealed that plants treated with T. virens DM5 exhibited rapid early activation of defense-associated pathways, including MAPK signaling, MYB transcription factors, and amino sugar metabolism within 24 h post inoculation, followed by attenuation of prolonged defense responses. These responses reduced the need for prolonged immune activation, suggesting an energy-saving strategy, allowing the plant to allocate resources toward development and survival. These findings highlight the multifaceted role of T. virens DM5 in sustaining tomato growth and disease suppression under A. rolfsii-conducive conditions. By combining direct antagonism with strategic modulation of plant defense, T. virens facilitates an optimized biocontrol–biostimulant trade-off. Understanding this interplay is critical for enhancing the efficacy of Trichoderma-based applications in climate-smart, sustainable agriculture. [Figure: see text] Copyright © 2026 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.