Biocontrol of Rhizoctonia solani K1 by Iturin A Producer Bacillus subtilis RB14 Seed Treatment in Tomato Plants

Bacillus subtilis RB14 was used as an antagonist against fungal pathogen Rhizoctonia solani K1 to control damping-off diseases in tomato plants. Tomato seeds were treated with B. subtilis RB14 culture. The concentration of bacterial cells for the treatment was about 108 cfu/ml. Treated tomato seeds showed 99% germination index similar to the untreated seeds. Scanning Electron Microscopic observations showed a clear evidence of the presence of B. subtilis RB14 on tomato seed surface. Clear inhibition zone was observed using treated seed in dual plate assay against R. solani K1. B. subtilis RB14 treated seed showed 80% reduction in disease incidence during in vivo plant experiments. B. subtilis RB14 produces lipopeptide antifungal antibiotic iturin A which could suppress R. solani K1. The phenomenon was supported by our observation where we found significant amount of iturin A from the root zone soil of the seed treated plants.