Identification of a Novel Paenibacillus polymyxa Strain and Its Biocontrol and Plant Growth-Promoting Effects

Strain CF05 isolated from Cryptomeria fortunei in Tianmu Mountain, Zhejiang province was identified as Paenibacillus polymyxa on the bases of its phenotypical and biochemical characteristics as well as 16 S rDNA gene sequence. The P. polymyxa CF05 exhibited highly antagonistic effects against 9 plant fungal pathogens and 3 plant bacterial pathogens in vitro. Furthermore, both cell-free fermentation and bacterial suspension promoted tomato seedlings growth in greenhouse assay. Cell-free fermentation increased the biomass with fresh weight and dry weight by 272.0% and 266.7%, respectively. It was demonstrated that secondary metabolites from this bacterium might perform a critical function in plant growth promotion. Tests of root-colonizing ability indicated that concentrations of the bacterium in tomato rhizosphere were 3.8, 3.6, 3.1 and 3.1 log CFU/g root after 27 days of inoculation of tomato seeds with the bacterial suspension at 108、107、106、105 CFU/mL, respectively. Seed germination ratio was increased by 11.7%, and the disease incidence of damping-off was reduced by 38.6% after seed treatment.