Lab and pot study finds Streptomyces curbs rice sheath blight

A strain of Streptomyces isolated from rice soil managed under rice–potato rotation showed antifungal activity against Rhizoctonia solani AG-1 IA, the fungus that causes rice sheath blight. In the reported laboratory and potted-plant experiments, Streptomyces murinus P-11 F inhibited the pathogen by 67.78% in dual-culture testing and delivered 46.40% disease control in pots, lowering the disease index from 84.46 to 46.34. Its cell-free culture supernatant also suppressed pathogen mycelial expansion, reaching 77.56% inhibition at a 5.00% dilution.

The research began by comparing soil microbial communities under rice–potato rotation and continuous rice monoculture. The investigators reported that rotation substantially improved soil quality and directionally reshaped microbial assemblages. Most notably for the biocontrol search, the relative abundance of Streptomyces was 2.5-fold higher in rotation-managed soil than under continuous rice cultivation.

Guided by these metagenomic observations, the team isolated and screened microorganisms from rice rhizosphere soil enriched by the rotation. P-11 F emerged as a novel strain with activity against R. solani. The supplied study abstract does not report the number of isolates screened or the individual measurements used to characterize the improvements in soil quality.

The dual-culture assay quantified inhibition of R. solani at 67.78%, while experiments with P-11 F’s cell-free supernatant tested whether activity remained without living bacterial cells. At a 5.00% dilution, the supernatant strongly suppressed pathogen mycelial expansion and produced an inhibition rate of 77.56%. Its retained activity shows that a soluble component of the culture preparation was associated with antifungal effects, although the reported evidence does not identify every active constituent.

In the potted-plant assay, application of P-11 F was associated with 46.40% disease control and a reduction in the disease index from 84.46 to 46.34. Metabolite profiling provided a more specific line of evidence for the strain’s antifungal mechanism. During co-cultivation with R. solani, P-11 F specifically produced 2-hydroxyphenazine, or 2-OH-PHZ.

When tested against the pathogen, 2-OH-PHZ showed dose-dependent antifungal activity, with an EC₅₀ of 48.75 µg/mL. The results therefore connect P-11 F with pathogen suppression through two measurable preparations—the bacterium itself and its cell-free supernatant—and identify 2-OH-PHZ as a compound produced specifically during interaction with R. solani. The reported data do not establish that this metabolite alone accounts for the supernatant’s full inhibition rate.

Taken together, the study presents rice–potato rotation as a way to enrich potentially antagonistic microorganisms through soil microbial legacy effects and provide a rhizosphere environment favorable to their proliferation. The authors frame this cropping practice as both a basis for targeted mining of disease antagonists and a source of germplasm for biocontrol screening. P-11 F and its supernatant showed strong activity against the targeted pathogen under the tested conditions, and the metabolite analysis supplied evidence for one mechanistic component of that activity.

Although the authors describe broad-spectrum potential for green biopesticide development, the results reported here focus on R. solani and rice sheath blight.

Subject of Research: Antifungal activity and metabolite mechanism of a Streptomyces strain selected from rotation-enriched rice rhizosphere soil

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

Article References: Wang, Y., Zeng, Y., Luo, Y., Fan, Q., Deng, Y., Zheng, S., Li, C., & Yang, G. (2026). Biocontrol potential and antifungal mechanism of Streptomyces sp. P-11 F against rice sheath blight. BMC Plant Biology. https://doi.org/10.1186/s12870-026-10177-6

Image Credits: AI Generated

DOI: 10.1186/s12870-026-10177-6

Keywords: rice sheath blight, Rhizoctonia solani, Streptomyces murinus, biological control, rice–potato rotation, 2-hydroxyphenazine, biopesticides, rhizosphere microbiome, antifungal activity, metagenomics, Biocontrol, potential