title: The volatile-producing Flavobacterium johnsoniae strain GSE09 shows biocontrol activity against Phytophthora capsici in pepper.
abstract: OBJECTIVE
  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.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratory of Plant Disease and Biocontrol, Division of Biotechnology, Korea University, Seoul, South Korea.
authors.forename: M K
authors.initials: MK
authors.lastname: Sang
authors.forename: K D
authors.initials: KD
authors.lastname: Kim
mesh_terms: D018441:Biofilms; D061046:Biological Control Agents; D002212:Capsicum / Q000382:microbiology*; D005417:Flavobacterium / Q000235:genetics / Q000502:physiology*; D010636:Phenols / Q000494:pharmacology; D010838:Phytophthora / Q000187:drug effects / Q000254:growth & development*; D010935:Plant Diseases / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D058441:Rhizosphere; D012988:Soil Microbiology; D013501:Surface-Active Agents
chemical_list: D061046:Biological Control Agents; D010636:Phenols; D012336:RNA, Ribosomal, 16S; D013501:Surface-Active Agents; C056559:2,4-di-tert-butylphenol