Laboratory of Plant Disease and Biocontrol, Division of Biotechnology, Korea University, Seoul, South Korea.
J Appl Microbiol. 2012 Aug;113(2):383-98. doi: 10.1111/j.1365-2672.2012.05330.x. Epub 2012 May 29.
Previously, we selected a bacterial strain (GSE09) antagonistic to Phytophthora capsici on pepper, which produced a volatile compound (2,4-di-tert-butylphenol), inhibiting the pathogen. In this study, we identified strain GSE09 and characterized some of the biological traits of this strain in relation to its antagonistic properties against P. capsici. In addition, we examined bacterial colonization on the root surface or in rhizosphere soil and the effect of various concentrations of the volatile compound and strain GSE09 on pathogen development and radicle infection as well as radicle growth.
Strain GSE09 was identified as Flavobacterium johnsoniae, which forms biofilms and produces indolic compounds and biosurfactant but not hydrogen cyanide (HCN) with little or low levels of antifungal activity and swimming and swarming activities. Fl. johnsoniae GSE09 effectively colonized on pepper root, rhizosphere, and bulk (pot) soil, which reduced the pathogen colonization in the roots and disease severity in the plants. Various concentrations of 2,4-di-tert-butylphenol or strain GSE09 inhibited pathogen development (mycelial growth, sporulation, and zoospore germination) in I-plate (a plastic plate containing a center partition). In addition, germinated seeds treated with the compound (1-100 μg ml⁻¹) or the strain (10²-10¹⁰ cells ml⁻¹) significantly reduced radicle infection by P. capsici without radicle growth inhibition.
These results indicate that colonization of pepper root and rhizosphere by the Fl. johnsoniae strain GSE09, which can form biofilms and produce indolic compounds, biosurfactant, and 2,4-di-tert-butylphenol, might provide effective biocontrol activity against P. capsici.
To our knowledge, this is the first study demonstrating that the Fl. johnsoniae strain GSE09, as a potential biocontrol agent, can effectively protect pepper plants against P. capsici infection by colonizing the roots.
此前，我们从辣椒上筛选到一株拮抗辣椒疫霉的细菌菌株（GSE09），其产生的挥发性化合物（2,4-二叔丁基苯酚）能抑制病原菌。本研究鉴定了菌株 GSE09，并对其与拮抗辣椒疫霉特性相关的一些生物学特性进行了描述。此外，我们还研究了细菌在根表面或根际土壤中的定殖，以及不同浓度的挥发性化合物和菌株 GSE09 对病原菌发育和胚根感染以及胚根生长的影响。
菌株 GSE09 被鉴定为黄杆菌属（Flavobacterium johnsoniae），该菌形成生物膜，并产生吲哚类化合物和生物表面活性剂，但产生氰化氢（HCN）的水平较低或几乎没有，抑菌活性、泳动和群集活性也较弱。Fl. johnsoniae GSE09 能有效定殖于辣椒根、根际和土壤（花盆），减少病原菌在根中的定殖和植株的发病程度。不同浓度的 2,4-二叔丁基苯酚或菌株 GSE09 均能抑制 I 板（含中心隔板的塑料板）中病原菌的发育（菌丝生长、孢子形成和游动孢子萌发）。此外，用该化合物（1-100μg ml⁻¹）或该菌株（10²-10¹⁰细胞 ml⁻¹）处理萌发的种子，能显著降低辣椒疫霉对胚根的感染，而不抑制胚根生长。
这些结果表明，能形成生物膜并产生吲哚类化合物、生物表面活性剂和 2,4-二叔丁基苯酚的 Fl. johnsoniae 菌株 GSE09 定殖于辣椒根和根际，可能为防治辣椒疫霉提供有效的生物防治活性。
据我们所知，这是首次研究表明，Fl. johnsoniae 菌株 GSE09 作为一种潜在的生防菌，通过定殖于根，可以有效地保护辣椒植株免受辣椒疫霉的感染。
