关键词: 立枯丝核菌, 番茄立枯病, 洋葱伯克氏菌, 防治效果, 抑菌物质

Abstract: In order to clarify the taxonomic status of strain B4-8 having biocontrol effect on tomato damping-off，and explore its biocontrol mechanism and safety for human being，this study carried out identification on strain B4-8 based on morphological，physiological and biochemical characteristics and 16S rDNA sequence analysis．The antifungal spectrum was determined by plate confrontation culture method，and its biocontrol effect on tomato damping-off was evaluated by pot experiment．The strain action mechanism was preliminarily analyzed by physiological，biochemical and molecular biological methods．The safety of strain B4-8 for plants and human being was determined by onion and lettuce leaf midrib infection models，and PCR amplification detecting gene BCESM（Burkholderia cepacia epidemic strain marker ）．The results showed that the antagonistic strain B4-8 was Burkholderia cepacia．This strain had stronger inhibitory activity on 6 pathogenic fungi，including Rhizoctonia solani，Fusarium oxysporum and Deightoniella torulosa，etc.．Its indoor control efficacy on tomato damping-off reached 71.43%．This strain could inhibit mycelial growth of tomato damping-off；had stronger ability of forming biofilm；could produce antimicrobial metabolites，including protease，chitinase and nitropyrrolidin，etc.．However，BCESM gene was not detected in strain B4-8 by PCR，and strain B4-8 was unable to cause pathogenicity of onion and lettuce leaf midrib，preliminarily indicating that it was safe for plants and human being，and had potential to control tomato damping-off．

Key words: Rhizoctonia solani, tomato damping-off, Burkholderia cepacia, control effect, antibacterial substance