Growth Promotion and Disease Suppression Ability of a Streptomyces sp. CB-75 from Banana Rhizosphere Soil

• Published in: Frontiers in microbiology Vol. 8; p. 2704
• Main Authors: Chen, Yufeng, Zhou, Dengbo, Qi, Dengfeng, Gao, Zhufen, Xie, Jianghui, Luo, Yanping
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 17.01.2018
• Subjects: antifungal activity; banana Fusarium wilt; biosynthetic genes; GC-MS; Microbiology; pot experiments; Streptomyces spectabilis; GC-MS; Streptomyces spectabilis; biosynthetic genes; banana Fusarium wilt; pot experiments; antifungal activity
• ISSN: 1664-302X; 1664-302X
• DOI: 10.3389/fmicb.2017.02704

An actinomycete strain, CB-75, was isolated from the soil of a diseased banana plantation in Hainan, China. Based on phenotypic and molecular characteristics, and 99.93% sequence similarity with NBRC 13424 (AB184393), the strain was identified as sp. This strain exhibited broad-spectrum antifungal activity against 11 plant pathogenic fungi. Type I polyketide synthase (PKS-I) and non-ribosomal peptide synthetase (NRPS) were detected, which were indicative of the antifungal compounds that sp. CB-75 could produce. An ethyl acetate extract from the strain exhibited the lowest minimum inhibitory concentration (MIC) against (ATCC 96167) (0.78 μg/ml) and yielded the highest antifungal activity against (ATCC 16330) (50.0 μg/ml). Also, spore germination was significantly inhibited by the crude extract. After treatment with the crude extract of sp. CB-75 at the concentration 2 × MIC, the pathogenic fungi showed deformation, shrinkage, collapse, and tortuosity when observed by scanning electron microscopy (SEM). By gas chromatography-mass spectrometry (GC-MS) of the crude extract, 18 chemical constituents were identified; ( )-13-docosenamide was the major constituent. Pot experiments showed that the incidence of banana seedlings was reduced after using sp. CB-75 treatment. The disease index was 10.23, and the prevention and control effect was 83.12%. Furthermore, sp. CB-75 had a growth-promoting effect on banana plants. The chlorophyll content showed 88.24% improvement, the leaf area, root length, root diameter, plant height, and stem showed 88.24, 90.49, 136.17, 61.78, and 50.98% improvement, respectively, and the shoot fresh weight, root fresh weight, shoot dry weight, and root dry weight showed 82.38, 72.01, 195.33, and 113.33% improvement, respectively, compared with treatment of fermentation broth without sp. CB-75. Thus, sp. CB-75 is an important microbial resource as a biological control against plant pathogenic fungi and for promoting banana growth.