Sustainable management of southern blight in peanut using volatile organic compounds produced by Bacillus amyloliquefaciens HK17.

Southern blight, caused by Sclerotium rolfsii, is a highly destructive soilborne fungal disease that severely impacts peanut production worldwide. The rapid spread and aggressive nature of this pathogen, coupled with its ability to produce sclerotia that can persist in soil for extended periods, make it a significant threat to global agriculture. This study explored the biocontrol potential of volatile organic compounds (VOCs) produced by Bacillus amyloliquefaciens HK17 as an alternative approach to managing southern blight in peanut. VOCs produced by strain HK17 in two different growth media-tryptic soy broth medium (TSB-HK17) and sterile compost-amended soil (SCS-HK17)-effectively inhibited the mycelial growth and sclerotia germination of S. rolfsii and disrupted the synthesis of oxalic acid, a key virulence factor of S. rolfsii. They also caused a significant reduction in the activity of plant cell wall-degrading enzymes associated with fungal pathogenicity. Gas chromatography-mass spectrometry analysis showed the VOCs belonged to several classes of compounds, including alcohols, amines, and sulfur-containing compounds, with amines being particularly dominant. Notably, 5-nonylamine was the most effective in reducing the growth of mycelia from both mycelial plugs and germinated sclerotia. Treatment with TSB-HK17- and SCS-HK17-produced VOCs significantly controlled S. rolfsii invasion in peanut plants compared to untreated controls. These results indicate that VOCs produced by B. amyloliquefaciens HK17 could be utilized as promising, environmentally friendly agents for the effective management of southern blight in peanut and other crops, offering a sustainable alternative to traditional chemical pesticides.