The growth-promoting and disease-suppressing mechanisms of inoculation on peanut seedlings.

spp. is known for its ability to enhance plant growth and suppress disease, but the mechanisms for its interaction with host plants and pathogens remain unclear. This study investigated the transcriptomics and metabolomics of peanut plants ( L.) inoculated with QT20045, in the absence and presence of the stem rot pathogen JN3011. Under the condition without pathogen stress, the peanut seedlings inoculated with QT20045 showed improved root length and plant weight, increased indole acetic acid (IAA) production, and reduced ethylene level, with more active 1-aminocyclopropane-1-carboxylate acid (ACC) synthase (ACS) and ACC oxidase (ACO), compared with the non-inoculated control. Under the pathogen stress, the biocontrol efficacy of QT20045 against was 78.51%, with a similar effect on plant growth, and IAA and ethylene metabolisms to the condition with no biotic stress. Transcriptomic analysis of peanut root revealed that inoculation upregulated the expression of certain genes in the IAA family but downregulated the genes in the ACO family ( and ) and ACS family ( and ) consistently in the absence and presence of pathogens. During pathogen stress, QT20045 inoculation leads to the downregulation of the genes in the pectinesterase family to keep the host plant's cell wall stable, along with upregulation of the gene to activate plant defense responses. antagonistic test confirmed that QT20045 suppressed growth through mechanisms of mycelial entanglement, papillary protrusions, and decomposition. Our findings highlight that inoculation is a promising tool for sustainable agriculture, offering multiple benefits from pathogen control to enhanced plant growth and soil health.