• Microbiology and Biotechnology Letters
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• v.32 no.4
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• pp.312-316
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• 2004

In oder to select the powerful rhizophere-dorminatable biocontrol agent, we had isolated an indigenous antagonistic bacterium which produced antibiotic and siderophore from a disease suppressive local field soil of Gyungsan, Korea. And we could select the Pseudomosp. 4059 which can strongly antagonize against Fusarium oxysporum and Phytophthora capsici by two kinds of antifungal mechanism that can be caused by the antibiotic of Phenazin, a siderophore and a auxin like subThe selected strain was identified as Pseudomonas fluorescens (biotype A) 4059 by biochemical tests, API $\textregistered$ test, MicroLog TM system and 16S rDNA analysis. The selected antagonistic microorganism, Pseudomosp. 4059 had an antifungal mechanism of antifungal antibiotic and sidrophore. And we were confirmed the antagonistic activity of P fluorescens 4059 with in vitro antifungal test against Phytophthora capsici and in vivo by red-pepper.

• 한국생물공학회:학술대회논문집
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• 2001.11a
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• pp.660-661
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• 2001

Pseudomonas sp. GRC3 produced extracellular chitinase(s) and ${\beta}$-1,3-glucanase(s), possible biocontrol agents. Both of enzymes appeared to inhibit the growth of plant phathogens, especially Phytophthora capsici. Antifungal activities of Pseudomonas sp. GRC3 determined was more than 78% inhibition rate against P. capsici.

• The Plant Pathology Journal
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• v.29 no.4
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• pp.418-426
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• 2013

Pseudomonas isolates from different crop plants were screened for in vitro growth inhibition of Phytophthora capsici and production of biosurfactant. Two in vivo experiments were performed to determine the efficacy of selected Pseudomonas strains against Phytophthora blight of pepper by comparing two fungicide treatments [acibenzolar-S-methyl (ASM) and ASM + mefenoxam]. Bacterial isolates were applied by soil drenching ($1{\times}10^9$ cells/ml), ASM ($0.1{\mu}g$ a.i./ml) and ASM + mefenoxam (0.2 mg product/ml) were applied by foliar spraying, and P. capsici inoculum was incorporated into the pot soil three days after treatments. In the first experiment, four Pseudomonas strains resulted in significant reduction from 48.4 to 61.3% in Phytophthora blight severity. In the second experiment, bacterial treatments combining with olive oil (5 mL per plant) significantly enhanced biological control activity, resulting in a reduction of disease level ranging from 56.8 to 81.1%. ASM + mefenoxam was the most effective treatment while ASM alone was less effective in both bioassays. These results indicate that our Pseudomonas fluorescens strains (6L10, 6ba6 and 3ss9) that have biosurfactant-producing abilities are effective against P. capsici on pepper, and enhanced disease suppression could be achieved when they were used in combination with olive oil.

• Research in Plant Disease
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• v.29 no.4
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• pp.440-444
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• 2023

In August 2021, water-soaking symptoms of bacterial spot disease were observed on castor bean in a field in Gangseo District, Busan. Bacteria isolated from the lesion when cultured on tryptic soy agar appeared to be nonmucoid and pale green. To confirm whether the isolates were the causative agent of the spot disease, they were inoculated onto healthy castor bean plants. The same symptoms were observed on the inoculated tissue, and the bacteria were reisolated from the lesion. Furthermore, the isolates were consistent with the biochemical and physiological features of Pseudomonas capsici. Sequencing analysis using 16S rRNA and housekeeping genes (gyrB, rpoD) showed that the isolates shared a high sequence similarity with P. capsici. These results confirmed that the strains belonged to P. capsici. To our knowledge, this is the first report of bacterial spot disease caused by P. capsici on castor bean in Korea.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.123-135
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• 2023

Previously, Pseudomonas plecoglossicida YJR13 and Pseudomonas putida YJR92 from a sequential screening procedure were proven to effectively control Phytophthora 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 (swimming 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 compared with Bacillus vallismortis EXTN-1 (positive biocontrol strain), Sphingomonas aquatilis KU408 (negative biocontrol strain), and MgSO₄ solution (untreated control). In diluted (nutrient-deficient) V₈ juice broth, the tested strain populations were maintained at >10⁸ cells/ml, simultaneously providing mycelial inhibitory activity. 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. Collectively, 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 together with chemotaxis to root exudates.

• Microbiology and Biotechnology Letters
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• v.28 no.6
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• pp.334-340
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• 2000

In order to select multifunctional powerful antagonistic biocontrol agent against red-pepper rotting fungi Phytophthora capsici, we isolated an indigenous antagonistic bacterium which produces antifungal substances and siderophores from a local soil of Kyongju, Korea. The isolated strain was identified as Pseudomonas fluorescens biotype F. The antibiotic produced from P. fluorescens 2112 inhibited hyphae growth and the zoospore germination of Phytophthora capsici. The favorable carbon, nitrogen source and salts for the production of antibiotic from P. fluorescens 2112 were glycerol, beef extract and LiCi at 1.0%, 0.5% and 5 mM, respectively. And antagonistic activity of P. fluorescens 2112 was confirmed against P. capsici in vivo.

• Microbiology and Biotechnology Letters
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• v.29 no.1
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• pp.37-42
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• 2001

An antifungal substance was purified from culture broth of Pseudomonas flulorescens 2112 that showed a broad-spectrum antagonistic activity against various phytopathogenic fungi including capsici. The substance was identified as 2,4-diacetylphloro-glucinol basd on NMR analysis. The 2,4-diacetylphloroglcinol showed antibiotic activity in broad acidic range from pH 1.0 to pH 9.0. About 83% of initial activity was remained after incubation for 30min ar $60^{\circ}C$, however, the activity was dropped up to 50% after 30 min incubation in $80^{\circ}C$. When the nucleotides of P. capsici treated with 2,4-diacetylphloroglucinol were labeled with[$^{3}$ H]-Adenin, the newly synthesized and radioactive-labeled RNA was significantly reduced than those of untreated P. capsici. indicating that the 2,4-diacetylphloroglucinol inhibits RNA synthesis.

• Journal of Microbiology and Biotechnology
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• v.3 no.1
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• pp.12-18
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• 1993

Pseudomonas aeruginosa strain B5 with antagonistic activity against Phytophthora capsici and Magnaporthe grisea, was isolated from pepper-growing soil. From the culture of P. aeruginosa strain B5 grown on King's medium B, antibiotic substances were purified using XAD-2 column chromatography. XAD-2 eluates inhibited not only the mycelial growth of P. capsid and M. grisea, but also the development of Phytophthora blight on pepper plants. The crude antibiotic substances were further purified by using silica gel column chromatography, Sephadex LH-20 column chromatography, thin layer chromatography on silica gel plates, and high performance liquid chromatography. Silica gel column chromatogrphy gave good separation of the four antibiotic substances. The pure antibiotics P1, P2, and P3 finally purified by preparative HPLC inhibited the mycelial growth of P. capsici, at concentrations from 7 to 10 $\mu g/ml$. Only P1 and P2 had antifungal activity against M. grisea at 8 $\mu g/ml$. P1 and P3 were highly inhibitory to the mycelial growth of Botryosphaeria dothidea and Botrytis cinerea at relatively low concentrations. However, the three antibiotics had no antifungal activity against Rhizoctonia solani. The chemical structures of these antibiotics are being identified.

• Korean Journal of Environmental Agriculture
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• v.15 no.3
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• pp.289-295
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• 1996

This study was attempted to select an antagonist against Phytophthora blight of red-pepper caused by Phytophthora capsici. The three strains, A-35, A-67 and A-183 were isolated from the rhizosphere in soil where red-pepper had been cultivated continuously for a long time, and the strain A-83 was estimated to be the strongest antagonist against P. capsici. The A-183 strain was identified as a strain of Pseudomonas sp., showing the maximum antifungal activity, when cultured at $30^{\circ}C$ for 5 days in the potato extract medium(pH 6.5) containing 2.0% mannitol and 0.3% peptone.

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.422-428
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• 2014

Endophytic bacterial strains from root tissue of strawberry were screened for their efficacy in growth improvement and control of Phytophthora blight disease of chili pepper plant under greenhouse condition. Plants treated with the strain EP103, identified as Pseudomonas fluorescens, showed growth improvement in terms of fresh weight and root length compared to the untreated control and other endophytic strains. When challenged with Phytophthora capsici, there was significant reduction of disease in EP103 treated plants with an efficacy of 78.7%. There was no direct inhibition of the target pathogen by EP103 when tested under in vitro antibiosis assay. Analysis of differential expression of selected marker genes for induced systemic resistance (ISR) in plants treated with EP103 and challenged with P. capsici showed up-regulation of PR1 and PR10 pathogenesis-related (PR) proteins. PCR analysis showed that EP103 produced secondary metabolites such as pyoluteorin, pyrrolnitrin, hydrogen cyanide and orfamide A. This study indicated the potential of endophytic P. fluorescens strain EP103 as an efficient biocontrol agent against P. capsici in chili pepper plant.