Abstract:Antagonistic bacterium FD6 was isolated from the canola rhizosphere in Fujian Province. In order to define the inhibitory mechanism and ability of the strain FD6 to Botrytis cinerea, the causal agent of grey mould on tomato, was detected using microscope concave slides method and on detached tomato leaves. The strain FD6 was identified based on 16S rDNA BLAST, the analysis of physiological and biochemical characterization. The antibiotics production of bacterial strain FD6 was analyzed by PCR amplification, thin layer chromatography (TLC) and TLC-bioautography. The results showed that the bacterial culture of strain FD6 significantly inhibited the spore germination with an inhibition rate of 99% for B.cinerea and 59.7% efficiency to control grey mould on detached tomato leaves, whereas the cultural filtrate of the strain FD6 only showed a low inhibition rate of 31%. The 16S rDNA sequence of the strain FD6 shared the 99% similarities with the members in Pseudomonas and the minimal genetic distance with Pseudomonas fluorescnes. Combined with the physiological and biochemical characteristics, the strain FD6 was identified as P.fluorescens. Strain FD6 produced multiple antifungal factors, including pyrrolnitrin, 2, 4-diacetylphloroglucinol, pyoluterorin, siderphore, hydrogen cyanide and extracellular proteinase, but not phenazine-1-carboxylic acid. The pyrrolnitrin inhibited directly the spore germination and mycelial growth of B.cinerea.