Biocontrol Potential of <i>Trichoderma asperellum</i> Strain 576 against <i>Exserohilum turcicum</i> in <i>Zea mays</i>

Maize is a crucial cereal crop in China, serving both as a staple food and an essential industrial resource. Northern corn leaf blight (NCLB) is a disease of corn caused by a fungus, <i>Exserohilum turcicum</i> (sexual stage <i>Setosphaeria turcica</i>). This study aimed to assess the biocontrol potential of various <i>Trichoderma</i> strains against <i>Exserohilum turcicum</i> 101 in Jilin, China. Through dual culture tests, the <i>Trichoderma</i> strains were categorized into four groups based on their antagonistic abilities. Eleven <i>Trichoderma</i> strains exhibited strong antagonistic behavior, with comparable or faster growth rates than <i>E. turcicum</i> 101. Microscopic observations confirmed that <i>T. asperellum</i> 576 hyphae effectively encircled <i>E. turcicum</i> 101 hyphae, reinforcing their antagonistic behavior. The production of non-volatile and volatile substances by the <i>Trichoderma</i> strains was evaluated, with <i>T. asperellum</i> 576 showing the highest potency in producing non-volatile and volatile substances, leading to an impressive 80.81% and 65.86% inhibition of <i>E. turcicum</i> 101 growth. Remarkably, co-culture suspensions of <i>T. asperellum</i> 576 + <i>E. turcicum</i> 101 and <i>T. atroviride</i> 393 + <i>E. turcicum</i> 101 exhibited strong antifungal activity. Furthermore, the activities of chitinase, β-1.3-glucanase, and cellulase were evaluated using the 3, 5-dinitrosalicylic acid (DNS) method. <i>T. asperellum</i> 576 + <i>E. turcicum</i> 101 displayed stronger cell wall degradation enzyme activity compared to <i>T. atroviride</i> 393 + <i>E. turcicum</i> 101, with values of 8.34 U/mL, 3.42 U/mL, and 7.75 U/mL, respectively. In greenhouse conditions, the application of a 10⁷ spores/mL conidia suspension of <i>T. asperellum</i> 576 significantly enhanced maize seed germination and plant growth while effectively suppressing <i>E. turcicum</i> 101 infection. Maize seedlings inoculated/treated with both <i>E. turcicum</i> 101 and <i>T. asperellum</i> 576 demonstrated substantial improvements compared to those inoculated solely with <i>E. turcicum</i> 101. The <i>T. asperellum</i> 576 treatment involved a 10⁷ spores/mL conidia suspension applied through a combination of foliar spray and soil drench. These findings highlight <i>T. asperellum</i> 576 as a promising biocontrol candidate against northern leaf blight in maize. Its antagonistic behavior, production of inhibitory compounds, and promotion of plant growth all contribute to its potential as an effective biocontrol agent for disease management.