# Isolation and Identification of Antifungal Polyketones from Bacillus velezensis DJ1 and Their Biocontrol Potential Against Corn Stalk Rot

## TL;DR

This study identifies antifungal compounds from Bacillus velezensis that effectively control corn stalk rot without harming soil microbes.

## Contribution

The study identifies difficidin and bacillaene as active antifungal polyketones from Bacillus velezensis with biocontrol potential.

## Key findings

- DJ1 polyketones inhibited Fusarium graminearum and reduced corn stalk rot by 44.33%.
- Polyketones caused morphological and plasma membrane damage in the fungus.
- The compounds did not disrupt the soil microbial community balance.

## Abstract

Corn, a major global food crop, is often damaged by Fusarium graminearum, which causes corn stalk rot and leads to serious yield losses. The objective of this study was to clarify the antifungal activity and underlying antifungal mechanism of polyketone compounds produced. In this study, the antifungal activity of DJ1-derived polyketones against F. graminearum were evaluated, while their effects on the morphological and functional characteristics of the fungus were examined. Additionally, the efficacy of these polyketones in reducing corn stalk rot incidence was assessed in a greenhouse, and their impacts on the soil microbial community were investigated. Results showed that DJ1 polyketones exerted effective inhibitory effects on F. graminearum, induced morphological and plasma membrane damage, and significantly reduced the occurrence of corn stalk rot with a disease control efficacy of 44.33%. Meanwhile, the polyketones did not disrupt the overall balance of the soil microbial community. Structural identification revealed that the bioactive components with antifungal activity were identified as difficidin and bacillaene. This research provides an effective strategy for the biocontrol of corn stalk rot.

Corn stalk rot, caused by Fusarium graminearum, severely threatens corn production, while chemical fungicides lead to resistance and environmental risks. Thus, exploring environmentally friendly biocontrol agents is crucial. Though Bacillus polyketones have antifungal activity, their active components, corn stalk rot biocontrol potential and rhizosphere impacts remain unclear. This study isolated polyketones from Bacillus velezensis DJ1, assessed their antifungal activity and mechanism against F. graminearum, verified greenhouse efficacy, analyzed rhizosphere microbiota, and identified active components via HPLC-HDMS Q-TOF. The results showed that DJ1 polyketones showed dose-dependent inhibition by disrupting F. graminearum’s mycelium and membrane, with 44.33% greenhouse control efficacy. They did not disturb rhizosphere balance, only increasing Bacteroidota and DYGX01, and the active components were difficidin and bacillaene. These findings confirm DJ1 polyketones as promising eco-friendly biocontrol agents, providing a new strategy for sustainable corn stalk rot management.