Previously, Pseudomonas plecoglossicida YJR13 and Pseudomonas putida YJR92 from a sequential screening procedure were proven to effectively control Phy-tophthora blight caused by Phytophthora capsici. In this study, we further investigated the anti-oomycete activities of these strains against mycelial growth, zoospore germination, and germ tube elongation of P. capsici. We also investigated root colonization ability of the bacterial strains in square dishes, including cell motility (swim-ming and swarming motilities) and biofilm formation. Both strains significantly inhibited mycelial growth in liquid and solid V8 juice media and M9 minimal media, zoospore germination, and germ tube elongation com-pared with Bacillus vallismortis EXTN-1 (positive bio-control strain), Sphingomonas aquatilis KU408 (negative biocontrol strain), and MgSO4 solution (untreated con-trol). In diluted (nutrient-deficient) V8 juice broth, the tested strain populations were maintained at >108 cells/ ml, simultaneously providing mycelial inhibitory activ-ity. Additionally, these strains colonized pepper roots at a 106 cells/ml concentration for 7 days. The root colonization of the strains was supported by strong swimming and swarming activities, biofilm formation, and chemotactic activity towards exudate components (amino acids, organic acids, and sugars) of pepper roots. Col-lectively, these results suggest that strains YJR13 and YJR92 can effectively suppress Phytophthora blight of pepper through direct anti-oomycete activities against mycelial growth, zoospore germination and germ tube elongation. Bacterial colonization of pepper roots may be mediated by cell motility and biofilm formation to-gether with chemotaxis to root exudates.
Bibliographical noteFunding Information:
Elena Volynchikova was supported by the Korean Government Scholarship Program (KGSP) during her PhD study at the Korea University, Seoul, Korea.
© The Korean Society of Plant Pathology.
- Phytophthora capsici
- Pseudomonas plecoglossicida
- Pseudomonas pu-tida
- bacterial colonization
ASJC Scopus subject areas
- Agronomy and Crop Science