Biocontrol potential and antifungal mechanism of Streptomyces sp. P-11 F against rice sheath blight

Background Rice sheath blight (RSB), caused by Rhizoctonia solani AG-1 IA ( R. solani ), is an extremely destructive soil-borne fungal disease that seriously threatens global rice production and food security. The efficacy of chemical control strategies has been declining, which highlights an urgent need for sustainable and environmentally friendly biocontrol alternatives. Rice‑potato rotation is a promising soil management practice that can modify rhizosphere microbial communities, yet its potential for mining antagonistic biocontrol actinobacteria remains insufficiently explored. Results We found that rice-potato rotation (RR)substantially improved soil quality and directionally reshaped soil microbial assemblages; the relative abundance of Streptomyces was 2.5‑fold higher compared with continuous rice monoculture (RM). Guided by these metagenomic findings, we further conducted microbial isolation and screening from rotation-enriched rice rhizosphere soil and obtained a novel biocontrol strain Streptomyces murinus P‑11 F.In dual‑culture testing, P‑11 F achieved an in‑vitro inhibition rate of 67.78% against R. solani , and yielded 46.40% disease control efficacy in potted‑plant assays, lowering the disease index from 84.46 to 46.34. The cell‑free supernatant (CFS) of P‑11 F strongly suppressed pathogen mycelial expansion, with an inhibition rate of 77.56% at a 5.00% dilution. Metabolite profiling identified 2‑hydroxyphenazine (2‑OH‑PHZ), a compound specifically produced by P‑11 F during co‑cultivation with R. solani . This metabolite displayed dose‑dependent antifungal activity against the pathogen, with an EC₅₀ of 48.75 µg/mL. Conclusion Rice–potato rotation enriches beneficial Streptomyces via soil microbial legacy effects and forms a microenvironment conducive to the proliferation of biocontrol microbes, providing a cropping basis and germplasm platform for targeted mining of disease antagonists and screening of biocontrol strains. Strain P‑11 F and its cell-free supernatant (CFS) possess stable and excellent broad-spectrum biocontrol potential for the development of novel green biopesticides.