Identification and characterization of Chryseobacterium wanjuense strain KJ9C8 as a biocontrol agent of Phytophthora blight of pepper Hye-Sook Kim a, 1 , 2 , Mee Kyung Sang a, b, 2 , Ho Won Jung c , Yong-Chull Jeun d , Inn-Shik Myung e , Ki Deok Kim a, * a Laboratory of Plant Disease and Biocontrol, Division of Biotechnology, Korea University, Seoul 136-713, South Korea b Institute of Life Science and Natural Resources, Korea University, Seoul 136-713, South Korea c Department of Genetic Engineering, Dong-A University, Busan 604-714, South Korea d College of Applied Life Science, Faculty of Bioscience and Industry, The Research Institute for Subtropical Agriculture and Biotechnology, Jeju National University, Jeju 690-756, South Korea e Crop Protection Division, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, South Korea article info Article history: Received 23 August 2011 Received in revised form 15 October 2011 Accepted 21 October 2011 Keywords: Antagonistic rhizobacteria Biological control Chryseobacterium wanjuense Phytophthora capsici Root colonization Swarming motility abstract Several Chryseobacterium species associated with the suppression of soilborne plant pathogens have been identified, but little is known about the properties of these antagonistic bacteria. In this study, we identified the previously isolated bacterial strain KJ9C8 as Chryseobacterium wanjuense, an effective biocontrol agent against Phytophthora blight of pepper caused by Phytophthora capsici, using Biolog, fatty acid methyl ester, phylogenetic, biochemical, and physiological analyses as well as transmission electron microscopy. Properties of C. wanjuense have been also investigated for its biocontrol activities, including colonization on pepper roots, microbial activity or population in bulk (pot) or rhizosphere soil, the productions of extracellular enzymes, antibiotics, biosurfactant, and hydrogen cyanide (HCN), and other related traits (swarming motility and biofilm formation). Strain KJ9C8 produced protease and HCN with swarming activity, but not antibiotics, biofilm, biosurfactant, and chitinase. In addition, C. wanjuense KJ9C8 effectively colonized on pepper roots, suggesting that this bacterium might be able to protect infection courts from soilborne plant pathogens. Furthermore, the survival of strain KJ9C8 in bulk or rhizosphere soil persisted as long as 4 weeks although it gradually decreased over time. Taken together, these results indicate that the colonization and survival of C. wanjuense strain KJ9C8, which produces protease and HCN with swarming activity, on pepper roots and in rhizosphere soil might confer effective biocontrol activities to this strain. Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. 1. Introduction Recently, the interest in biological control by beneficial microor- ganisms (Kim et al., 2008a, 2008b, 2009; An et al., 2010; Sang et al., 2011) or composts (Sang et al., 2010; Sang and Kim, 2011) has increased consistently as an alternative disease control to substitute for various hazardous chemical controls against airborne or soil- borne plant pathogens (Lamour and Hausbeck, 2000; Kim et al., 2008c; Kim and Kim, 2009). In this regard, some rhizobacterial strains isolated from root surface or interior have been known as beneficial microorganisms and have been utilized as biocontrol agents. These beneficial bacteria have the ability to colonize rhizo- sphere or roots and/or to produce secondary metabolites including antibiotics, extracellular enzymes, hydrogen cyanide (HCN), side- rophores, and phytohormones (Kamilova et al., 2005; Kim et al., 2009). For effective and reliable methods to control plant diseases using biocontrol agents under field conditions, it is important to understand the characteristics of bacterial strains that possess biocontrol activities, including their root colonization, and survival and protection of infection courts from plant pathogens (McSpadden Garderner and Weller, 2001; Kamilova et al., 2005). In addition, some beneficial bacterial strains can enhance or induce plant resistance and promote plant growth (Han et al., 2005; Sang et al., 2011). Phytophthora blight by (Phytophthora capsici Leonian) causes severe yield loss on pepper plants worldwide and the disease is difficult to control due to rapid reproduction, dissemination of zoospores and dormant structures of the pathogen (Lamour and Hausbeck, 2000). Microorganisms such as Bacillus spp., Paenibacillus * Corresponding author. Tel.: þ82 2 3290 3065; fax: þ82 2 925 1970. E-mail address: kidkim@korea.ac.kr (K.D. Kim). 1 Present address: Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, IL 60637, USA. 2 The first two authors contributed equally to this work. Contents lists available at SciVerse ScienceDirect Crop Protection journal homepage: www.elsevier.com/locate/cropro 0261-2194/$ e see front matter Crown Copyright Ó 2011 Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.cropro.2011.10.018 Crop Protection 32 (2012) 129e137