Abstract:

An antagonistic bacterium was found in pomegranate fruit and identified as Bacillus subtilis according to its morphology, physiological and biochemical characteristic and 16S rDNA molecular sequence. Antagonistic characteristics displayed that this strain was able to obviously inhibit growth of eight pathogens. For plant pathogenic fungi of Botryosphaeria dothidea, B. parvaand Zythia versoniana, which infect fruits of different trees, the antagonistic bacterium increased mycelia to branch and caused some mycelial cells to distort and fracture and protoplasm to condense. With the bacterium infected, the top and middle mycelial cells intumescentiaed into sphere and oval or bead-like, some intumescentiaed mycelial top cells obviously clustered together and the color became dark, with the mycelial cell intumescentiaed, the cells turned more transparent and changed into vacuole at last. But for Valsa sordida pathogen causing poplar rot disease, the antagonistic bacterium caused mycelia cells to become slim and fragile and less branch. There was no obvious mycelial tops and the cells did not intumescentia into sphere or bead-like, some mycelia were digested and hard to be recognized. All the above results demonstrated that the antagonistic bacterium had different acting mechanism to different causal pathogens.

Key words: pomegranate fruit, antagonistic bacterium, identification, antibacterial characteristic, acting mechanism