Antimicrobial activities of an oxygenated cyclohexanone derivative isolated from Amphirosellinia nigrospora JS-1675 against various plant pathogenic bacteria and fungi.

AIMS: To evaluate the antimicrobial activities of an active compound isolated from the culture broth of Amphirosellinia nigrospora JS-1675 against various plant pathogenic bacteria and fungi.

METHODS AND RESULTS: While screening for bioactive secondary metabolites from endophytic fungi, we found that Amphirosellinia nigrospora JS-1675 showed strong in vitro antibacterial activity against Ralstonia solanacearum. One compound (1) was isolated and identified as (4S, 5S, 6S)-5, 6-epoxy-4-hydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one. Growth of most of the tested phytopathogenic bacteria was inhibited by compound 1 and the ethyl acetate (EtOAc) layer except Pseudomonas syringae pv. lachrymans. Compound 1 also inhibited the mycelial growth of several plant pathogenic fungi. Both compound 1 and the EtOAc layer reduced bacterial leaf spot disease in detached peach leaves. They also suppressed the development of bacterial wilt on tomato seedlings quite effectively.

CONCLUSIONS: A. nigrospora JS-1675 showed antimicrobial activity against plant pathogenic bacteria and fungi by producing compound 1.

SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the occurrence of compound 1 in A. nigrospora JS-1675 and its efficacy against plant pathogenic bacteria and fungi. Their strong disease control efficacy against tomato bacterial wilt suggests that this fungus can be used as a microbial bactericide. This article is protected by copyright. All rights reserved.