Phenotypic characterization of Pseudomonas fluorescens PfG32R and its spontaneous gacS mutants and biocontrol activity against bacterial wilt disease of tomato |
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Authors: | W Gusti Ngurah Alit-Susanta Yuichi Takikawa |
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Institution: | (1) Laboratory of Plant Pathology, Faculty of Agriculture, Shizuoka University, 836 Ohya, Shizuoka 422-8529, Japan;(2) The United Graduate School of Agricultural Science, Gifu University, Gifu, Japan;(3) Faculty of Agriculture, Udayana University, Jl. PB. Sudirman, Denpasar, Bali, Indonesia |
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Abstract: | Pseudomonas fluorescens strain PfG32R actively suppresses the occurrence of bacterial wilt disease of tomato caused by Ralstonia solanacearum. To determine the characteristics affected by spontaneous mutations in the gacS gene, three spontaneous mutants NR1, NR9, and ASW6 were tested for production of several enzymes, antimicrobial activity,
and biocontrol activity against bacterial wilt disease of tomato in a greenhouse. Production of biosurfactant and of enzymes
such as Tween-80 lipase, gelatin protease, and lecithinase; swarming activity; and antifungal activities against Fusarium oxysporum f. sp. radicis-lycopersici and F. graminearum were inactivated by mutations in the gacS gene, indicating that they are under the regulation of the GacS/GacA two-component regulatory system. Levan production, swimming,
antifungal activity against Magnaporthe grisea, and antibacterial activity against R. solanacearum and Erwinia carotovora ssp. carotovora were not controlled by the GacS/GacA system. Biocontrol activities of the three spontaneous mutants varied from strain to
strain, indicating that the biocontrol activities of PfG32R are influenced not only by the GacS/GacA system but also by other
complex factors, which may not be regulated by the system. |
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Keywords: | Pseudomonas fluorescens gacS mutants Bacterial wilt of tomato Swarming Biosurfactant Antimicrobial activity |
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