Molecular Characterization and Biocontrol Potential of Native Rhizobacteria Against Rhizoctonia solani in Rice
Screening 32 native soil bacteria from Karnataka rice fields, researchers found two Streptomyces strains that cut sheath blight severity as effectively as a chemical fungicide — with hydrogen cyanide and iron-starving siderophores identified as their weapons against the fungus.
- ▸Of 32 native rhizobacterial isolates collected from rice rhizosphere soil across four Karnataka growing regions, the actinobacterial strains GVTAM 8 and DWRAM 10 inhibited R. solani mycelial growth by 90.61% and 88.38% in vitro — outperforming even the established reference biocontrol strain AUDT 502 (87.77%).
- ▸In glasshouse trials, combined seed treatment plus foliar spraying with GVTAM 8 and AUDT 502 was the single best treatment, cutting relative lesion height to 14.52% — statistically on par with the chemical fungicide hexaconazole (14.04%) and a dramatic improvement over the untreated, pathogen-only control (65.40%).
- ▸16S rRNA gene sequencing identified GVTAM 8 as Streptomyces cinnabarinus (98.06% similarity to reference sequences) and DWRAM 10 as Streptomyces pseudogriseolus (98.21% similarity), with both sequences deposited to NCBI (accession numbers OQ512000 and OQ512154).
- ▸The biocontrol effect is attributed to two specific mechanisms: hydrogen cyanide production, which disrupts the pathogen's electron transport chain and halts ATP synthesis, and siderophore production, which starves the fungus of iron it needs to survive by binding available ferric ions first.