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Chinese Journal of Biological Control ›› 2022, Vol. 38 ›› Issue (3): 613-625.DOI: 10.16409/j.cnki.2095-039x.2022.02.022

• RESEARCH REPORTS • Previous Articles    

Study on Biocontrol Mechanism of Bacillus amyloliquefaciens JK10 to Control Blueberry Crown Gall Disease

YAO Bo1, ZHANG Jinhao1, HE Yilu1, LIANG Xuqing2, CUI Xingguo3, RONG Langfei2, ZHOU Xinghai1, WEI Fangjun1, HE Zulei1, JI Guanghai1, WEI Lanfang2   

  1. 1. State Key Laboratory for Conservation and Utilization of Bio-Resources in Yunnan, Yunnan Agricultural University, Kunming 650201, China;
    2. Agricultural Foundation Experiment Teaching Center, Yunnan Agricultural University, Kunming 650201, China;
    3. Qujing Jiawo Modern Agriculture Company, Qujing 655000, China
  • Received:2021-11-15 Published:2022-06-20

Abstract: Crown gall disease caused by Agrobacterium tumefaciens is a serious threat to blueberry production. In this study, we aimed to explore the biocontrol mechanism of Bacillus amyloliquefaciens JK10 to manage crown gall disease of blueberry via pot and field experiments. We extracted crude extract with the maximum antibacterial activity against A. tumefaciens from the fermentation medium of B. amyloliquefaciens JK10, using four methods:acid precipitation, ammonium sulfate precipitation, ethyl acetate extraction, and microporous resin adsorption. High-throughput sequencing technique was used to investigate the bacterial community structure associated with blueberry healthy root tissue, crown gall root tissue, and crown gall root tissue treated with B. amyloliquefaciens JK10. Furthermore, B. amyloliquefaciens JK10 was labeled with a green fluorescent protein (GFP) to confirm its colonization ability in the blueberry plant parts. Results of this study, demonstrated that the crude extract obtained by four methods have strong antagonistic effects on A. tumefaciens.Among all methods, the crude extract obtained by the macroporous resin adsorption method has maximum antibacterial activity. Two types of lipopeptide compounds bacillomycin D and fengycin, and the macrolide antibiotic Divergolide D and the polyketide Bacillaene, were detected in the crude extract of B. amyloliquefaciens JK10. Confocal microscopy micrographs revealed that B. amyloliquefaciens JK10 can successfully colonize the intercellular spaces of blueberry roots and emits fluorescence light. Whereas, plate culture methods were adopted to confirm the colonization ability in the blueberry leaf tissues, which showed that B. amyloliquefaciens JK10 also colonized in the blueberry leaf as fluorescence color was oberved under UV-light. The number of B. amyloliquefaciens JK10 stabilized in the rhizosphere soil of blueberry and the leaves of blueberry were 1×106cfu/g and 4.0×105cfu/g, respectively, after 35 days of post inoculation. Application of B. amyloliquefaciens JK10 significantly increased the alpha diversity (richness) and beta diversity (community structure) indices as compared with control (untreated diseased blueberry plants). The species diversity was increased and the structure tends to be healthier in blueberry diseased plants treated with B. amyloliquefaciens JK10 compared with control. In summary, we conclude that B. amyloliquefaciens JK10 mitigates the crown gall disease of blueberry through production of antibacterial substances that inhibit the growth of crown gall pathogen, niche exclusion (sharing space with pathogen), and by changing the bacterial community structure. Altogether, our study demonstrates the possible biocontrol mechanism of B. amyloliquefaciens JK10 to manage blueberry crown gall disease.

Key words: Bacillus amyloliquefaciens, Agrobacterium tumefaciens, biocontrol, high-throughput sequencing, colonize, antibacterial substance

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