A promising strain of endophytic Streptomyces sp. for biological control of cucumber anthracnose

• Published in: Journal of general plant pathology : JGPP 2009-02, Vol.75 (1), p.27-36
• Main Authors: Shimizu, M.(Mie Univ., Tsu (Japan)), Yazawa, S, Ushijima, Y
• Format: Article
• Language: English
• Subjects: Agriculture; Bacteria; BIOLOGICAL CONTROL; BIOLOGICAL DIFFERENCES; Biomedical and Life Sciences; COLLETOTRICHUM; Colletotrichum orbiculare; CONCOMBRE; CONTROL BIOLOGICO; Crop diseases; CUCUMBERS; Cucumis sativus; Cucurbita moschata; DIFERENCIAS BIOLOGICAS; DIFFERENCE BIOLOGIQUE; EXPERIMENTACION IN VIVO; EXPERIMENTATION IN VIVO; Fungal Diseases; Fungi; IN VIVO EXPERIMENTATION; Leaves; Lesions; Life Sciences; LUTTE BIOLOGIQUE; MICROBIAL PESTICIDES; Microbiology; Pathogens; PEPINO; PESTICIDE MICROBIEN; PLAGUICIDAS MICROBIANOS; Plant biology; Plant Pathology; Seedlings; STREPTOMYCES; Vegetables
• ISSN: 1345-2630; 1610-739X
• DOI: 10.1007/s10327-008-0138-9

In a survey for effective biocontrol agents of Colletotrichum orbiculare, causal agent of cucumber anthracnose, 43 (MBCu series) and 135 (MBPu series) endophytic actinomycete strains were recovered from surface-sterilized organs of cucumber (Cucumis sativus) and pumpkin (Cucurbita moschata) plants, respectively. The strains were cultured with C. orbiculare on IMA-2 agar medium to determine their in vitro antagonistic ability. Eleven strains that strongly inhibited hyphal growth of the pathogen were selected as potent antagonists. Detached cotyledons of cucumber were soaked in a spore suspension of an antagonistic strain 1 day before challenge-inoculation with the pathogen, and six of these antagonists (MBCu-32, 36, 42, 45, and 56, and MBPu-75) significantly reduced the number and size of the lesions on the cotyledons compared to the untreated control. In the same way, these six strains inhibited lesion development on attached leaves of 3-week-old cucumber seedlings. Strain MBCu-56, the most suppressive of the strains, was selected for further tests. Its suppressiveness increased as concentrations increased; pretreatment of leaves with the strain at 10E7, 10E8 and 10E9 cfu/ml suppressed disease by 72, 79 and 93%, respectively. These results strongly indicated that MBCu56 has strong potential for controlling cucumber anthracnose. Based on the taxonomic characteristics and 16S rDNA sequence, MBCu-56 was identified as Streptomyces sp. With scanning electron microscopy, the substrate mycelia of the strain were seen to colonize the surface of leaves above the cuticle. Some hyphae also penetrated and grew underneath the cuticle.