Biocontrol of Phytopathogen by Pseudomonas fluorescens R21, Isolated from Rice Rhizosphere in Thailand

Abstract

Secondary metabolites produced by fluorescent Pseudomonas play key roles in the suppression of various soilborne plant pathogens. However, the performance of this biocontrol agent varies depending on the environment and host plant species. In this study, In vitro antagonistic activity against phytopathogens by Pseudomonas fluorescens R21, which was isolated from rice rhizosphere in Thailand, was investigated in comparison to Pseudomonas fluorescens F113, which was isolated from sugar beet rhizosphere in Ireland. The result of in vitro antagonistic activity showed that Pythium spp. was suppressed by strains R21 and F113. Then, strain R21 that has the ability to produce IAA and to control plant pathogen was investigated for in vivo antagonistic activity and also was screened for the production of secondary metabolites such as pyoluteorin, pyrrolnitrin, hydrogen cyanide and 2,4-diacetylphloroglucinol (DAPG). The result of in vivo antagonistic activity confirmed that Pythium spp. was suppressed by strains R21 and F113. In addition, the application of strain R21 to rice seeds significantly increased plant height, shoots dry weight and roots dry weight of rice while the application of strain F113 to rice seeds showed no significant difference when compared to control.