Efficacy assessment of antifungal metabolites from Chaetomium globosum No.05, a new biocontrol agent,against Setosphaeria turcica

Northern corn leaf blight (NCLB), an important and potentially destructive corn foliar disease, is caused by Setosphaeria turcica. The intent of this study was to evaluate antifungal metabolites from Chaetomium globosum (Cg) strain No.05 to suppress NCLB in maize. This strain significantly suppressed mycelial growth of numerous phytopathogenic fungi especially S. turcica on potato dextrose agar medium. The secondary metabolites of the strain inhibited mycelial growth and conidial germination of S. turcica. When co-inoculated at three droplets (5 μL/droplet) of conidial suspension (5 × 10⁴ conidia/mL) on each 8-cm-long detached leaf, 20% culture filtrates completely suppressed disease incidence of northern corn leaf blight. The application of the culture filtrates at 2 h post-inoculation (hpi) of S. turcica in greenhouse studies showed a 81.9% inhibition of NCLB on the seedlings, while culture filtrates applied before pathogen inoculation showed even higher rates of disease reduction. The application of the culture filtrates had no observed effects on the treated maize leaves or seedlings. Two active compounds, isolated from the extracts, were identified as chaetoglobosin A and chaetoglobosin C based on the spectroscopic analysis. Both in vitro and in planta bioassay experiments showed that chaetoglobosin A displayed potent biocontrol efficiency against S. turcica. To the best of our knowledge, this is the first report of the evaluation of the inhibitory effects of C. globosum and chaetoglobosin A against S. turcica both in vitro and on detached maize leaves.