Serratia marcescens Sm85 produces dimethyl disulfide defense against rice sheath blight and effects on phyllosphere bacterial community

Abstract BACKGROUND Rice sheath blight (RSB), caused by Rhizoctonia solani Kuhn, significantly impacts rice yield and quality. The extensive use of chemical pesticides, while often effective, requires high application rates, causes environmental damage, is expensive, and contributes to the development of pesticide resistance. The lack of reliability and robustness of these conventional techniques necessitates the development of sustainable and environmentally friendly agricultural practices. Identifying novel biological control agents is crucial for developing effective and eco‐friendly strategies to manage RSB. RESULTS This study identifies S . marcescens 85 (Sm85), isolated from rice stems, as a potential biocontrol agent against RSB. Sm85 produces the volatile chemical dimethyl disulfide (DMDS), which has antagonistic activity both in vivo (67.4% effective) and in vitro (97.7% effective). DMDS disrupts pathogen cell membrane integrity by increasing reactive oxygen species (ROS) production and reducing ergosterol content. The pot experiments demonstrated that DMDS treatment significantly reduces RSB lesion length, with a control effect comparable to commercial fungicides. The high‐throughput data revealed that DMDS application alters the phyllosphere microbial community structure, increasing its richness and diversity. Notably, DMDS treatment enriches potentially beneficial bacteria such as Stenotrophomonas and Burkholderia , known for their roles in plant stress tolerance and pesticide degradation. Functional gene analysis reveals an upregulation of sulfur metabolism‐related genes in the phyllosphere microbiome, suggesting adaptive responses to DMDS. CONCLUSION This study highlights the potential of Sm85 and its volatile metabolite DMDS as eco‐friendly alternatives for RSB management, while also emphasizing the importance of considering microbial community dynamics in biocontrol strategies. © 2025 Society of Chemical Industry.