Ralstonia solanacearum is an important soil-borne bacterial plant pathogen. In this study, an actinomycete strain named NEAU-HV9 that showed strong antibacterial activity against
Ralstonia solanacearum was isolated from soil using an in vitro screening technique. Based on physiological and morphological characteristics and 98.90%
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Ralstonia solanacearum is an important soil-borne bacterial plant pathogen. In this study, an actinomycete strain named NEAU-HV9 that showed strong antibacterial activity against
Ralstonia solanacearum was isolated from soil using an in vitro screening technique. Based on physiological and morphological characteristics and 98.90% of 16S rRNA gene sequence similarity with
Streptomyces panaciradicis 1MR-8
T, the strain was identified as a member of the genus
Streptomyces. Tomato seedling and pot culture experiments showed that after pre-inoculation with the strain NEAU-HV9, the disease occurrence of tomato seedlings was effectively prevented for
R. solanacearum. Then, a bioactivity-guided approach was employed to isolate and determine the chemical identity of bioactive constituents with antibacterial activity from strain NEAU-HV9. The structure of the antibacterial metabolite was determined as actinomycin D on the basis of extensive spectroscopic analysis. To our knowledge, this is the first report that actinomycin D has strong antibacterial activity against
R. solanacearum with a MIC (minimum inhibitory concentration) of 0.6 mg L
−1 (0.48 μmol L
−1). The in vivo antibacterial activity experiment showed that actinomycin D possessed significant preventive efficacy against
R. solanacearum in tomato seedlings. Thus, strain NEAU-HV9 could be used as BCA (biological control agent) against
R. solanacearum, and actinomycin D might be a promising candidate for a new antibacterial agent against
R. solanacearum.
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