In this study, the cocktail medium significantly enhanced antifungal metabolite production, thereby improving the suppression of peanut web blotch caused by Peyronellaea arachidicola. A novel antagonistic bacterial strain was isolated from cultivated peanut soil and identified as Bacillus velezensis WY-65. Additionally, the metabolomic profile of strain WY-65 was investigated under two fermentation conditions: basic fermentation medium (BFM) and cocktail fermentation medium (CFM). In vitro assays revealed that the cell-free supernatant (CFS) from WY-65 cultured in CFM inhibited P. arachidicola by 87.68%, whereas the CFS from BFM inhibited P. arachidicola by 61.42%. Greenhouse trials targeting peanut web blotch demonstrated that CFM achieved a disease control efficiency of 92%, whereas BFM exhibited a control efficiency of 86%. Treatment with CFM reduced the disease incidence to 8.71%, and BFM treatment resulted in a disease incidence of 15%. In contrast, the control group presented a disease incidence of 95%. CFS significantly impacted the efflux pump and caused ROS in P. arachidicola. Using untargeted LC‒MS/UHPLC-based metabolomics, we identified distinct metabolic signatures influenced by medium composition, revealing an enrichment of bioactive secondary metabolites, including 3-indoleacrylic acid and L-tryptophan, in CFM. KEGG differential abundance (DA) analysis revealed that strain WY-65 cultured in CFM underwent broad metabolic reprogramming, with significant enrichment in amino acid biosynthesis and the phenylalanine, tyrosine, and tryptophan synthesis pathways. Pathway topology analysis further revealed that glycine, serine, and threonine metabolism and phenylalanine, tyrosine, and tryptophan synthesis pathways had the greatest impact and significance, highlighting their central roles in stress adaptation and antimicrobial precursor biosynthesis. In vitro confirmatory tests with synthetic chemicals confirmed the bioactivity of these compounds. At 200 μL, both 3-indoleacrylic acid and L-tryptophan exhibited peak antifungal activity (91% and 89%, respectively), whereas their activities at 150 μL (87% vs. 75%) and 300 μL (89% vs. 80%) were comparatively lower. Our findings provide insight into medium-induced metabolomic modulation in strain WY-65 and highlight its potential as a robust biocontrol agent for sustainable peanut web blot disease management. Not applicable.
Ahsan et al. (Wed,) studied this question.