Interaction of Trichoderma Species with Fusarium graminearum Growth and Its Trichothecene Biosynthesis as Further Contribution in Selection of Potential Biocontrol Agents

The interactions of <i>Fusarium graminearum</i> PG-Fg1 and its main trichothecenes with the 28 <i>Trichoderma</i> isolates were studied in vitro. The antagonistic effect assessed by dual-culture tests showed that <i>Trichoderma</i> isolates arrested the growth of PG-Fg1 after contact, overgrew the PG-Fg1 colony and inhibited the production of deoxynivalenol (DON), 3-acetyl-deoxynivalenol (3-ADON), and 15-acetyldeoxynivalenol (15-ADON) by up to 95.3%, 99.4%, and 99.6%, respectively. PG-Fg1 was hard to overgrow <i>Trichoderma</i> for further extension. Additionally, the inhibitory effects on PG-Fg1 by the <i>Trichoderma</i> metabolites, including volatiles and non-volatiles, were also investigated. Most of the <i>Trichoderma</i> isolates produced metabolites which inhibited PG-Fg1 growth and mycotoxins production. Specifically, <i>Trichoderma</i> non-volatiles and volatiles showed <i>Fusarium</i> growth inhibition rates ranging from 7% to 72% and 3% to 32%, respectively. Notably, non-volatile compounds from two isolates and volatiles from one isolate up-regulated the expression of DON biosynthesis genes (tri4 and tri5), leading to increased production of DON, 3-ADON, and 15-ADON. This study highlights the potential risk posed by certain <i>Trichoderma</i> strains as microbial agents, which can stimulate toxigenic fungi to produce higher levels of mycotoxins. Based on our results and previous reports, when selecting <i>Trichoderma</i> species as biocontrol agents against <i>Fusarium graminearum</i>, its effects on mycotoxins production should be carefully assessed, particularly given observed stimulatory impacts.