Abstract:

The 78 strains were collected from the soil and were prescreened to have antagonistic activity against Ceratosphaeria phyllostachydis. A strain named 6-59 with a relatively higher antagonistic activity was obtained via re-screening. Then the strain 6-59 was characterized by morphological and culture features observation, physiological and biochemical measurements and 16SrDNA sequence analysis. Based on the data, the strain was initially identified as Bacillus megaterium. Through organic solvent extracting and （NH₄）₂SO₄ salting out to the fermentation liquid, the antagonistic substance produced by the stain 6-59 was inferred to a protein. Then the fermentation conditions of the strain 6-59 was studied via single factor experiments and orthogonal experiments, and the optimal shaking flask fermentation condition was determined as follows: a medium composed of 2% sucrose, 3% peptone, 0.03% MgSO₄·7H₂O, 0.02% KCl, seed age 18 h, initial pH of the medium 7.0, medium 50 mL in a 250 mL flask, inoculum size 4% and fermentation time 72 h. In this optimized conditions, the inhibition zone diameter of the fermentation liquid could reach to 25.8 mm.

Key words: top blight of bamboo, Ceratosphaeria phyllostachydis, antagonistic bacterium, screening, identification, antagonistic substance