Abstract

Two different actinomycete strains (XAS585 and XAS588), producing antifungal substances, were isolated from the marine mud of coast and offshore Zhuhai city, Guangdong province, China. On the basis of micro-morphology, physiological and chemotaxonomic characterization and phylogenetic similarity of 16S rDNA gene sequences, the strains XAS585 and XAS588 were identified as Streptomyces roseobiolascens XAS585 and Streptomyces roseofulvus XAS588, respectively. Antifungal profiles of the ethyl acetate extracts of the two strains fermented broth (FBE) were evaluated against the test phytopathogenic fungi; the results showed that the FBE of S. roseobiolascens XAS585 exhibited strong antifungal activity against mycelia growth of all test fungi at 150 µg/ml, while the FBE of S. roseobiolascens XAS588 also exhibited strong antifungal activity, except Sclerotinia scleroitiorum, Valsa mali and Cercospora sorghi at 150 µg/ml. In addition, the FBE of both strains at 100 μg/ml showed inhibitory effect against the condina germination of Alternaria alternate, Exserlhilum turcicum and Bipolaris sorokiniana. This study showed that the two marine-derived Streptomyces may provide potent sources for antifungal metabolites.

Key words: Actinomycete, phytopathogenic fungi, antimicrobial activity, marine mud, Streptomyces roseobiolascens XAS585, Streptomyces roseofulvus XAS588.