Previously, we selected bacterial strain ISE14 through a sequential selection procedure that included radicle, seedling, and in planta assays and field tests. This strain not only suppressed a destructive soilborne disease, Phytophthora blight, caused by Phytophthora capsici but also increased fruit yields of pepper plants in the fields. This study was conducted to identify strain ISE14 by 16S rRNA gene sequence analysis and to characterise biocontrol and plant growth promotion activities of the strain in pepper plants. Strain ISE14, identified as Chryseobacterium sp., significantly reduced disease severity in plants inoculated with Ph. capsici and promoted plant growth (lengths and dry weights of shoots and roots) compared with those in plants treated with Escherichia coli DH5α (negative control) or MgSO4 solution (untreated control). This strain effectively colonised pepper plant roots as assessed by bacterial population analysis and confocal laser scanning microscopy; it enhanced soil microbial activity and biofilm formation, but not the production of indole acetic acid. Strain ISE14 also solubilised organic or inorganic phosphate by production of acid and alkaline phosphatases or reduction in pH, resulting in enhanced pepper plant growth. This strain exhibited similar or greater activity in disease control and plant growth promotion tests compared with positive control strains Paenibacillus polymyxa AC-1 (biocontrol) and Bacillus vallismortis EXTN-1 (plant growth). Therefore, Chryseobacterium sp. ISE14 may be a phosphate-solubilising and plant growth-promoting rhizobacterium (PGPR) strain that suppresses Phytophthora blight of pepper. To our knowledge, this is the first report of a phosphate-solubilising PGPR strain of Chryseobacterium sp. that suppresses the pepper disease.
Bibliographical noteFunding Information:
This study was supported by the Basic Science Research Program of the National Research Foundation of Korea, funded by the Ministry of Education, Science and Technology (Project No. 2011-0013463). J.-J. J. was supported by the Global PhD program through the National Research Foundation of Korea, funded by the Ministry of Education (2015-034526), Korea. We thank Dr Kyungseok Park for providing the gfp-donor Escherichia coli strain.
© 2018 Association of Applied Biologists
- Biological control
- Phytophthora capsici
- phosphate solubilisation
- plant growth-promoting rhizobacteria
- root colonisation
ASJC Scopus subject areas
- Agronomy and Crop Science