Abstract:In order to develop an effective biocontrol measure against apple tree canker caused by Valsa ceratosperma, 63 bacterium strains were isolated and screened from the soil around the cultured apple root in Qixia, Shandong Province. The strain BJ1 which had significantly antagonistic effect on V.ceratosperma, was obtained using flat confrontation culture method. The inhibition rates of BJ1 and its fermentation supernatant were 78.38% and 70.54%, respectively. The antagonistic spectrum and the inhibitory efficiency of BJ1 on the conidial germination and hyphal growth of V.ceratosperma were investigated. The results showed that BJ1 could significantly reduce the conidial germination rate and induce alterations on mycelia morphology, such as deformity, branch increasing and cytoplasm exosmosis. In addition, BJ1 showed obvious antifungal activities on several fruit tree pathogenic fungi, such as Sclerotinia laxa, Phomopsis perniciosa and V.leucostoma. Based on the morphologic, physiological, biochemical characteristics and 16S rDNA sequence analysis, the strain BJ1 was defined as Stenotrophomonas acidaminiphila. The strain BJ1 fermentation supernatants with different dilution time exerted obvious inhibitory efficiency on V.ceratosperma growth in detached apple twigs. The control efficiency could reach 81.06% when the supernatant was diluted by fifty times. These results indicated that the strain BJ1 promised to provide a new biological control method in containing apple canker.