• Proceedings of the Korean Society of Life Science Conference
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• 2003.05a
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• pp.69-70
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• 2003

• Proceedings of the Korean Society of Life Science Conference
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• 2003.05a
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• pp.71-72
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• 2003

• Journal of Microbiology and Biotechnology
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• v.22 no.3
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• pp.326-330
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• 2012

Antifungal metabolites were isolated from a culture of Pseudomonas aurantiaca IB5-10. Chemical structures of the metabolites were elucidated as phenazine-1-carboxylic acid (PCA; 1), 2-hydroxyphenazine (2-OH-PHZ; 2), and cyclo-(L-Pro-L-Val; 3), respectively, based on spectroscopic methods. Among them, 3 was isolated for the first time from this strain. The antifungal activities of 1-3 were evaluated against a variety of plant pathogens. To the best of our knowledge, the antifungal activities of 3 against plant fungal pathogens have been evaluated for the first time in this work. PCA (1) showed the most potent antifungal activities against Phytophthora capsici, Rhizoctonia solani AG-1(IA), and Pythium ultimum with MICs (${\mu}g/ml$) of less than 1.0, 1.3, and 2.0, respectively. On the other hand, 2-OH-PHZ (2) showed potent antifungal activity against R. solani AG-1(IA) with the MIC (${\mu}g/ml$) of 2.0, whereas it showed moderate antifungal activity against P. ultimum with the MIC (${\mu}g/ml$) of 50.0. In addition, 3 showed antifungal activity against only R. solani AG-1(IA).

• The Plant Pathology Journal
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• v.17 no.1
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• pp.36-39
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• 2001

The secondary effects of pencycuron on cell membrane of Rhizoctonia solani AG4 were investigated by the observation of giant protoplast formation and lipid peroxidation. Compared to protoplasts of R. solani R-C (sensitive strain) and Rh-131 (non-sensitive strain) increased in their size by 2.0-3.5 times 12 h after incubation in potato-dextrose broth containing novozyme (7 mg/$m\ell$) and $\beta$-glucuronidase ($60\mu\textrm{g}/$\textrm{ml}) with 0.6 M mannitol (pH 5.2). The increase of protoplast size in R-C was slightly inhibited from $13.8\textrm{mg}/\textrm{ml}$ without pencycuron to 10.3 ${\mu}{\textrm}{m}$ with 1.0$\mu\textrm{g}$/$m\ell$ of pencycuron. However, the size of giant protoplast of Rh-131 was not affected by the pencycuron treatment. Both strains R-C and Rh-131 did not exhibit the lipid peroxidation 12 h after the application of 1.0 $\mu\textrm{g}$/$m\ell$ pencycuron. The remarkable peroxidation of membrane lipid was observed only in R-C 24 h after pencycuron application, but not in Rh-131. Althought the inhibition of giant protoplast formation and the membrane lipid peroxidation were observed only in the sensitive strain R-C by pencycuron, it is difficult to conclude that these are the primary mechanism of pencycuron. The mild activity of pencycuron on the inhibition of giant protoplast formation and late membrane lipid peroxidation in the fungicide-sensitive strain did not noincid with the dramatic activity of pencycuron in R. solani. Therefore, our results suggest that inhibition of giant protoplast formation and membrane lipid peroxidation is the secondary effect of pencycuron.

• The Plant Pathology Journal
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• v.32 no.2
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• pp.85-94
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• 2016

Studies were conducted to determine the role of 3-methylthioproprionic acid (MTPA) in the pathogenicity of potato stem canker, Rhizoctonia solani, and the concentrations required to inhibit growth of R. solani under laboratory and plant house-based conditions. The experiments were laid out in a completely randomized design with five treatments and five replications. The treatments were 0, 1, 2, 4, and 8 mM concentrations of MTPA. The purified toxin exhibited maximal activity at pH 2.5 and $30^{\circ}C$. MTPA at 1, 2, 4, and 8 mM levels reduced plant height, chlorophyll content, haulm fresh weight, number of stolons, canopy development, and tuber weight of potato plants, as compared to the control. MTPA significantly affected mycelial growth with 8 mM causing the highest infection. The potato seedlings treated with MTPA concentrations of 1.0-8.0 mM induced necrosis of up to 80% of root system area. Cankers were resulted from the injection of potato seedling stems with 8.0 mM MTPA. The results showed the disappearance of cell membrane, rough mitochondrial and cell walls, change of the shape of chloroplasts, and swollen endoplasmic reticulum. Seventy-six (76) hours after toxin treatment, cell contents were completely broken, cytoplasm dissolved, and more chromatin were seen in the nucleus. The results suggested that high levels of the toxin concentration caused cell membrane and cytoplasm fracture. The integrity of cellular structure was destroyed by the phytotoxin. The concentrations of the phytotoxin were significantly correlated with pathogenicity and caused damage to the cell membrane of potato stem base tissue.

• Plant Disease and Agriculture
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• v.1 no.1
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• pp.19-29
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• 1995

A microbial product composed of three antagonistic fungal isolates (Aspergillus sp., Penicillium sp. and Trichoderma sp.) and three bacterial isolates (Arthrobacter sp., Bacillus sp., and Pseudomonas sp.) was tested for the control of Pythium blight caused by Pythium sp., brown patch by Rhizoctonia solani (anastomosis group(AG) 1-1) and large patch by R. solani (AG 2-2) of turfgrasses. Cultures of the antagonistic fungi and bacteria varied in the effectiveness in reducing disease severity of Pytium blight and brown patch on bentgrass. The antagonistic fungal and bacterial isolates were mixed and cultured at 20-$25^{\circ}C$ for 3 days in a growth medium, and the diluted solution of the microbial culture was applied under the field conditions after inoculation of the above turfgrass pathogens. The treated turfgrass was incubated at 28$^{\circ}C$ in a growth chamber. In this experiment, Pythium blight was almost completely controlled and brown patch was slightly decreased by the microbial product, while no control was observed in large patch of zoysiagrass. In zoysiagrass treated with the microbial culture, thatch accumulation was notably reduced.

• Journal of Ginseng Research
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• v.28 no.4
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• pp.183-190
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• 2004

On May of 2002, the 34 isolates of Rhizoctonia solani were isolated from the symptom of damping-off on basal stems of 2-year-old to 6-year-old Panax ginseng which were cultivated in the 17 fields in Kyunggi-do, Chun­gcheungnam-do and Jeollabuk-do province in Korea. All isolates were identified as anastomosis group 2-1. Pre-emer­gence damping-off occurred on underground part of stem of 2-year-old ginseng in the pot trial with artificial inoculation. However, in the 4-year-old ginseng field with artificial inoculation, post-emergence damping-off occurred. The severe incidence of damping-off was found in the 6-year-old ginseng field in Kimje-si, Jeollabuk-do province on June 5 of 2003, the rate of which showed $18.6{\%}$ of area in the field by spread of the disease since 2-year-old. The sclerotia of R. solani, started to be formed after 7 days incubation on potato dextrose agar at $25^{\circ}C,$ were grayish brown, spherical to irregular and about $500{\mu}m$ in diameter, which became dark brown after 14 days incubation. The temperature range for the myce­lial growth of R. solani isolates was $5\~30^{\circ}C,$ and the optimal temperature was $25^{\circ}C,$ their growth were very poor at $5\;or\;30^{\circ}C$. The isolates grew at the range of pH $4.5\~8.1$ tested and optimal pH for growth was pH 4.5$\~5.8%, whereas their growth were very poor above the pH 7.2.

• Korean journal of applied entomology
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• v.26 no.2 s.71
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• pp.89-97
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• 1987

Antagonistic microorganisms from rhizosphere soil were isolated, identified, and applied successfully as the biocontrol agents of damping-off caused by Rhizoctonia spp. Rhizosphere antagonists isolated from rhizosphere soil were identified as Trichoderma viride, T. harzianum, T. hamatum, T. polysporum, Gliocladium sp., Pseudomonas fluorescence, P. stutzeri, P. cepacia, Enterobacter sp., Serratia sp. and Erwinia herbicola. Of these, the most promising ones in vitro were T. virdie, T. harzianum, Gliocladium sp., Serratia sp., P. stutzeri, and P. cepacia. These above six antagonists were efficient in reducing disease incidence to $40{\sim}70%$ when the reselected rhizosphere antagonists preparations were applied to the soil at $10^6$ propagules per gram. Among six antagonists, T. viride was the most promising biocontrol agents against R. solani isolates in soil. The suppressive effect was more evident in steam-sterilized soil than in non-sterilized field soil.

• Journal of Life Science
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• v.12 no.4
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• pp.416-422
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• 2002

Bacillus ehimensis YJ-37 was observed as a potential biological agent to control the occurrence of diseases and plant growth.promoting rhizobacteria (PGPR). Population density of B. ehimensis YJ-37 were higher 1.2~2 times in main roots and lateral roots than from nonrhizosphere soil and persisted around 10$^4$g root on the watermelon and radish root system upto 30 days after growing in pot condition. As a PGPR, B. ehimensis YJ-37 enhanced plant growth of watermelon and radish by soil treatment. The leaf area, hypocotyl length, root length and dry weight of radish were about 85, 33, 23 and 89% more than that of untreated plant, respectively. In case of watermelon were about 63, 27, 25 and 69% more than that of untreated plant, respectively. Biocontrol of damping-off in watermelon and radish caused by Rhizoctonia solani AG-4 and Pythium ultimum were carried out in pots using 3. ehimensis YJ-37. The results showed that might contribute to it's suppression of damping-off disease in field plants.

• Weed & Turfgrass Science
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• v.4 no.4
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• pp.348-359
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• 2015

Total 443 isolates of actinomycetes were isolated from turfgrass rhizosphere as potential biological control agents. The two isolates (S11 and S4) showed highest cellulase activity with compared to the other isolates that exhibited a clear zone of 1.2 mm around the colony on cellulose agar medium. S12 strain appeared the most active chitin degrading, which exhibited a 1.2 mm of clear zone. The highest proteolytic activity on skim milk agar was which exhibited a 7.5 mm of clear zone by S2 strain. S1 strain from the soli showed siderophore production ability, which exhibited a 0.6 mm of large clear zone on chrome azurol S agar. The antifungal activity of the volatile compound producing by 4 selected actinomycetes was investigated that inhibition rate against Rhizoctonia solani AG2-2 and Sclerotinia homoeocarpa. Growth inhibition effect of S8 isolate against S. homoeocarpa was appeared to 94.8%, S2 to 76.9%, S5 to 46.1% and S12 to 43.5%. The significant inhibition effects on mycelial growth of S. homoeocarpa were shown on media with four strains. The inhibition effect was the highest with S8 strain treatment at 94.8%.