• Mycobiology
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• v.42 no.3
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• pp.262-268
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• 2014

Several postharvest diseases of table grapes (Vitis vinifera) occur during storage, and gray mold rot is a particularly severe disease because the causal agent, Botrytis cinerea, grows at temperatures as low as $0^{\circ}C$. Other postharvest diseases, such as those caused by Penicillium spp. and Aspergillus spp., also often lead to deterioration in the quality of table grapes after harvest. The use of plant essential oils such as thymol and linalool, to reduce postharvest diseases in several kinds of fruits, including table grapes and oranges, has received much attention in European countries. However, to the best of our knowledge there has been no report of the use of thymol fumigation to control gray mold in table grapes in Korea. Thymol ($30{\mu}g/mL$) and linalool ($120{\mu}g/mL$) significantly inhibited mycelial growth and conidia germination of B. cinerea. The occurrence rate of gray mold rot of B. cinerea and other unknown fungi was significantly reduced by fumigation with $30{\mu}g/mL$ thymol in several table grape cultivars, such as Campbell early, Muscat Bailey A, Sheridan, and Geobong. In this study, fumigation with $30{\mu}g/mL$ thymol, had no influence on the sugar content and hardness of grapes, but reduced fungal infection significantly. This suggests that $30{\mu}g/mL$ thymol could be utilized to reduce deterioration of grapes due to gray mold and other fungal infections during long-term storage.

• Journal of Plant Biotechnology
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• v.4 no.1
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• pp.1-6
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• 2002

Plants have developed a sophisticated battery of defence responses to protect themselves against attempted pathogen ingress. Manipulation of these defence mechanisms may provide significant opportunities for crop improvement. While plant resistance genes have had a long service history in plant breeding, they possess significant limitations. Recent advances are now providing significant insights into strategies designed to increase the field durability of this class of genes. Hypersensitive cell death is a common feature underlying the deployment of plant defence responses against biographic pathogens. In contrast, necrotrophic pathogens actively kill plant cells. Recently, transgenic plants have been developed that either promote or suppress cell death, providing resistance against either biotrophic or necrotrophic pathogens respectively. Methyl-jasmonate is a key signalling molecule in the establishment of resistance against some fungal pathogens. Increasing the concentration of this molecule in plant cells has been shown to increase resistance against Botrytis cineria, without significantly imparting plant growth or development. Due to the multifarious infection strategies employed by plant pathogens, how-ever, it is unlikely a single commercial product will prove a panacea for global disease control. Future stategies will more likely entail an integrated disease management approach.

• Journal of Microbiology and Biotechnology
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• v.12 no.2
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• pp.235-241
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• 2002

Sophorolipid, a biosurfactant produced from Candida bombicola ATCC 22214, showed antimicrobial activity against Bacillus subtilis, Staphylococcus xylosus, Streptococcus mutans, and Propionibacterium acne at 4, 1, 1, 0.5 ppm, respectively. Also, 100 ppm of sophorolipid inhibited $50\%$ of cell growth of plant pathogenic fungus, Botrytis cineria. However, sophorolipid showed no effect on Escherichia coli, indicating that its selective antimicrobial activity depended on the cell wall structure. Treatment of B. subtilis with sophorolipid increased leakage of intracellular enzyme, malate dehydrogenase, indicating a possible interaction of sophorolipid with a cellular membrane. Comparing lactone-type and acid-type sophorolipids, the former showed a higher antimicrobial activity. Supplementing other surfactants showed no significant effects on the antimicrobial activity. Animal study showed that 5 g of sophorolipid per kg body weight by oral administration caused no toxicity, and sophorolipid induced no irritation on the skin. These results show potential use of sophorolipid as an active ingredient in healthcare products.

• Journal of Microbiology
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• v.41 no.3
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• pp.196-201
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• 2003

The object of this study was to characterize Bacillus strains GB-017 and GB-0356, which produce antifungal substances, especially for plant pathogens. In addition, this study was undertaken to characterize the culture conditions required for the production of antifungal substances and to document some of the properties of the antifungal substance produced by these soil-isolated strains. Strains GB-0365 and GB-017 were found to be bacillus-shaped, gram-positive and motile, and to inhibit Botrytis cineria, Fusarium sp., Pythium sp., and Rhizoctonia solani. Antagonistic activity was maintained up to pH 9.0, and the antifungal activity was stable to heat at 80$^{\circ}C$ for 1 h. Antifungal substances were separated and purified using ion exchange and adsorption columns including WK-I0(H$\^$＋) (pH 7.0), HP20 column (pH 3.0) and IPA (pH 3.0). and IPA. Its UV absorption spectrum showed major peaks at 231 and 259 nm, corresponding to polyene and lactone. A fast atom bombardment mass spectrum (FAB MS) showed a highest peak at 441 m/z and major peaks at 192, 205, and 370 m/z.

• Journal of Microbiology and Biotechnology
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• v.15 no.6
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• pp.1402-1407
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• 2005

The fungicidal activities of Coptis japonica (Makino) extracts and their active principles were determined against Botrytis cineria, Erysiphe graminis, Phytophthora infestans, Puccinia recondita, Pyricularia grisea, and Rhizoctonia solani using a whole plant method in vivo, and compared with natural fungicides. The responses varied according to the plant pathogen tested. At 2,000 mg/l, the chloroform and butanol fractions obtained from methanolic extracts of C. japonica exhibited strong/moderate fungicidal activities against B. cinerea, E. graminis, P. recondita, and Py. grisea. Two active constituents from the chloroform fractions and one active constituent from the butanol fractions were characterized as isoquinoline alkaloids, berberine chloride, palmatine iodide, and coptisine chloride, respectively, using spectral analysis. Berberine chloride had an apparent $LC_{50}$ value of approximately 190, 80, and 50 mg/l against B. cinerea, E. graminis, and P. recondita, respectively; coptisine chloride had an $LC_{50}$ value of 210,20, 180, and 290 mg/l against B. cinerea, E. graminis, P. recondita, and Py. grisea, respectively; and palmatine iodide had an $LC_{50}$ value of 160 mg/l against Py. grisea. The isoquinoline alkaloids were also found to be more potent than the natural fungicides, curcumin and emodin. Therefore, these compounds isolated from C. japonica may be useful leads for the development of new types of natural fungicides for controlling B. cinerea, E. graminis, P. recondita, and Py. grisea in crops.

• The Plant Pathology Journal
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• v.28 no.4
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• pp.364-372
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• 2012

Xanthomonas oryzae pv. oryzae causing bacterial leaf blight disease in rice produces and secretes Hpa1 protein that belongs to harpin protein family. Previously it was reported that Hpa1 induced defense responses when it was produced in tobacco. In this study, we expressed hpa1 gene in rice and Arabidopsis to examine the effects of Hpa1 expression on disease resistance to both fungal and bacterial pathogens. Expression of hpa1 gene in rice enhanced disease resistance to both X. oryzae pv. oryzae and Magnaporthe grisea. Interestingly, individual transgenic rice plants could be divided into four groups, depending on responses to both pathogens. hpa1 expression in Arabidopsis also enhanced disease resistance to both Botrytis cineria and Xanthomonas campestris pv. campestris. To examine genes that are up-regulated in the transgenic rice plants after inoculation with X. oryzae pv. oryzae, known defense-related genes were assessed, and also microarray analysis with the Rice 5 K DNA chip was performed. Interestingly, expression of OsACS1 gene, which was found as the gene that showed the highest induction, was induced earlier and stronger than that in the wild type plant. These results indicate that hpa1 expression in the diverse plant species, including monocot and dicot, can enhance disease resistance to both fungal and bacterial plant pathogens.

• Journal of Microbiology and Biotechnology
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• v.7 no.2
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• pp.107-113
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• 1997

A strain producing a high amount of chitinase was isolated from soil, identified as Pseudomonas sp., and tentatively named Pseudomonas sp. YHS-A2. An extracellular chitinase of Pseudomonas sp. YHS-A2 was purified according to the procedure of ammonium sulfate saturation, affinity adsorption, Sephadex G-100 gel filtration and Phenyl-sepharose CL-4B hydrophobic interaction column chromatography. The molecular weight of the purified enzyme was estimated to be 55 kDa on SDS-PAGE was confirmed by active staining. Optimal pH and temperature of the enzyme are pH 7.0 and $50^{\circ}C$, respectively, and the enzyme is stable between pH 5.0 and 8.0 and below $50^{\circ}C$. The main products of colloidal chitin by the chitinase were N-acetyl-D-glucosamine and N,N'-diacetylchitobiose both of which were detected by HPLC analysis. The enzyme is supposed to be a random-type endochitinase which can degrade any position of ${\beta}$-l,4-linkages of chitin and chitooligosaccharides. The chitinase inhibited the growth of some phytopathogenic fungi, Fusarium oxysporum, Botrytis cineria, and Mucor rouxii and these antifungal effects were thought to be due to the characteristics of endochitinase.

• 한국생물공학회:학술대회논문집
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• 2003.04a
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• pp.40-44
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• 2003

Soil-borne infectious disease including Pythium aphanidermatum and Rhizoctonia solani causes severe damage to plants, such as cucumber. This soil-borne infectious disease was not controlled effectively by chemical pesticide. Since these diseases spread through the soil, chemical agents are usually ineffective. Instead, biological control, including antagonistic microbe can be used as a preferred control method. An efficient method was developed to select an antagonistic strain to be used as a biological control agent strain. In this new method, surface tension reduction potential of an isolate was included in the ‘decision factor’ in addition to the other factors, such as growth rate, and pathogen inhibition rate. Considering these 3 decision factors by a statistical method, an isolate from soil was selected and was identified as Bacillus sp. GB16. In the pot test, this strain showed the best performance among the isolated strains. The lowest disease incidence rate and fastest seed growth was observed when Bacillus sp. GB16 was used. Therefore this strain was considered as plant growth promoting rhizobacteria (PGPR). The action of surface tension reducing component was deduced as the enhancement of wetting, spreading, and residing of antagonistic strain in the rhizosphere. This result showed that new selection method was significantly effective in selecting the best antagonistic strain for biological control of soil-borne infectious plant pathogen. The antifungal substances against P. aphanidermatum and R. solani were partially purified from the culture filtrates of Bacillus sp. GB16. In this study, lipopeptide possessing antifungal activity was isolated from Bacillus sp. GB16 cultures by various purification procedures and was identified as a surfactin-like lipopeptide based on the Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), high performance liquid chromatography mass spectroscopy (HPLC-MS), and quadrupole time-of-flight (Q-TOF) ESI-MS/MS data. The lipopeptide, named GB16-BS, completely inhibited the growth of Pythium aphanidermatum, Rhizoctonia solani, Penicillium sp., and Botrytis cineria at concentrations of 10 and 50 mg/L, respectively. A novel method to prevent the foaming and to provide oxygen was developed. During the production of surface active agent, such as lipopeptide (surfactin), large amount of foam was produced by aeration. This resulted in the carryover of cells to the outside of the fermentor, which leads to the significant loss of cells. Instead of using cell-toxic antifoaming agents, low amount of hydrogen peroxide was added. Catalase produced by cells converted hydrogen peroxide into oxygen and water. Also addition of corn oil as an oxygen vector as well as antifoaming agent was attempted. In addition, Ca-stearate, a metal soap, was added to enhance the antifoam activity of com oil. These methods could prevent the foaming significantly and maintained high dissolved oxygen in spite of lower aeration and agitation. Using these methods, high cell density, could be achieved with increased lipopeptide productivity. In conclusion to produce an effective biological control agent for soil-borne infectious disease, following strategies were attempted i) effective screening of antagonist by including surface tension as an important decision factor ii) identification of antifungal compound produced from the isolated strain iii) novel oxygenation by $H_2O_2-catalase$ with vegetable oil for antifungal lipopeptide production.

• The Korean Journal of Pesticide Science
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• v.13 no.4
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• pp.267-274
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• 2009

This study was carried out to select effective preventive pesticides against pine wilt disease caused by pinewood nematode (PWN), Bursaphelenchus xylophilus on trunk injection. 1,000 fold aquatic solution of abamectin 1.8% EC and emamectin benzoate 2.15% EC were lower mortality (7.3% and 8.3% respectively) against PWN on 1 day after treatment. However effects of abamectin 1.8% EC, emamectin benzoate 2.15% EC, fosthiazate 30% SL and fenitrothion 30% SL were inhibited the reproduction of PWN over 99.6% in Botrytis cineria media. Effect of trunk injection of abamectin 1.8% EC and emamectin benzoate 2.15% EC at the rate of $10\;m{\ell}$ per 10 cm in diameter of breast height (DBH) on mortality of Japanese black pine, Pinus thungergii by inoculated PWN was 0% and 3.3%, respectively at the applied year however when injection of fosthiazate 30% SL were treated with the rate of $5\;m{\ell}$ per 10 cm tree DBH, mortality of tree was 63.3%. Abamectin 1.8% EC and emamectin benzoate 2.15% EC was showed high preventive efficacy representing >90% against PWN at the following year. PWN preventing efficacy of trunk injection was lower in naturally occurred area (mortality of pine tree in control was 11.7% at the first year) of PWN than artificially infected site (mortality of pine tree in control was >76.7% at the first year), PWN preventing efficacy of trunk injection of abamectin 1.8% EC and emamectin benzoate 2.15% EC at the rate of $10\;m{\ell}$ per 10 cm in DBH was 91.5% and 82.9%, respectively, at the applied year and 89.5% and 82.6% respectively at the following year in PWN naturally occurred site. Control efficacy by trunk injection of abamectin 1.8% EC and emamectin benzoate 2.15% EC was more higher in 10 fold dilution with 10 fold high amount of aquatic solution than no dilution with 10 fold less amount of aquatic solution. The preventive effect of trunk injection of abamectin 1.8% EC and emamectin benzoate 2.15% EC at the rate of $5\;m{\ell}$ per 10 cm in DBH was showed 100% at the applied year in PWN inoculated tree.