• Korean Journal of Medicinal Crop Science
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• v.14 no.4
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• pp.202-205
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• 2006

Ginseng is major medicinal plant in Korea. Because of its long cultivation period the yield losses of 5 years of ginseng is 50% due to various diseases. The objective of this study is to select potential biocontrol agents. As the result of research so far achieved to contribute to rational prevention of ginseag plant disease for the stable cultivation of ginseng, three bacterial strains, Streptomyces lauretii strain B8180, Bacillus subtilis strain 8856, and Burkholderia cepacia strain 7944 were isolated from oak leaf compost. The strains showed antagonistic activities against five ginseng pathogenic fungi (Cylindrocarpon destructans, Rhizoctonia solani, Phytophthora cactorum, Botrytis cinerea, Fusarium solani f. sp. panacis) and control effects on Phytophthora blight.

• Research in Plant Disease
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• v.23 no.2
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• pp.89-98
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• 2017

Ralstonia solanacearum species complex (RSSC) causes bacterial wilt, and it is one of the most important soil-borne plant pathogenic bacteria. RSSC has a large host range of more than 50 botanical families, which represent more than 200 plant species, including tomato. It is difficult to control bacterial wilt due to following reasons: the bacterial wilt pathogen can grow inside the plant tissue, and it can also survive in soil for a long period; moreover, it has a wide host range and biological diversity. In most previous studies, scientists have focused on developing biological control agents, such as antagonistic microorganisms and botanical materials. However, biocontrol attempts are not successful. Plant-derived metabolites and extracts have been promising candidates to environmentally friendly control bacterial wilt diseases. Therefore, we review the plant extracts, essential oils, and secondary metabolites that show potent in vivo antibacterial activities (in potted plants or in field) against tomato bacterial wilt, which is caused by RSSC.

• 한국균학회소식:학술대회논문집
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• 2014.10a
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• pp.47-47
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• 2014

Dokdo island is located in the northeastern part of Ulleungdo, known as volcanic island. In total, 53 fungal isolates were isolated from Dokdo island soil sample, using dilution plate technique. The isolates were identified on the basis of morphological characteristics and rDNA ITS sequence analysis. Out of them, 41 isolates were identified at the level of species. The dominant fungal species and genera included Fusarium spp., Mucor sp., Clonostachys spp., and Trichoderma sp. The % sequence identity (the number of matches/the complete alignment length) values via NCBI BLAST searching of EML-IF9, EML-MF30-1 and EML-DDSF4 represented 97.19% (485/499) with Clonostachys cf. rosea (GenBank accession no. KC313107), 98.33% (472/480) with Metarhizium guizhouense (GenBank accession no. HM055445), and 100% (350/350) with Mortierella oligospora (GenBank accession no. JX976032), respectively. Three species of C. rosea, M. guizhouense and M. oligospora represented new records of fungi from Dokdo island, Korea. The antimicrobial activities of the fungal strains varied with tested. Two isolates (EML-MFS30-1 and EML-IF9) showed antifungal activity against several fungi including Fusarium oxysporum and Rhizotonia solani. Clonostachys rosea (EML-IF9) showed strong hydrolytic enzyme activity. Our results showed that the antagonistic fungi including Clonostachys rosea will be used as potential biocontrol agents for control of fungal diseases.

• Journal of Microbiology and Biotechnology
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• v.28 no.6
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• pp.1030-1036
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• 2018

Bacillus strains produce various types of antibiotics, and random mutagenesis has traditionally been used to overproduce these natural metabolites. However, this method leads to the accumulation of unwanted mutations in the genome. Here, we rationally designed a single nucleotide substitution in the degU gene to generate a B. subtilis strain displaying increased plipastatin production in a foreign DNA-free manner. The mutant strain (BS1028u) showed improved antifungal activity against Pythium ultimum. Notably, pps operon deletion in BS1028u resulted in complete loss of antifungal activity, suggesting that the antifungal activity strongly depends on the expression of the pps operon. Quantitative real-time PCR and lacZ assays showed that the point mutation resulted in 2-fold increased pps operon expression, which caused the increase in antifungal activity. Likewise, commercial Bacillus strains can be improved to display higher antifungal activity by rationally designed simple modifications of their genome, rendering them more efficient biocontrol agents.

• Korean journal of applied entomology
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• v.27 no.3
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• pp.159-164
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• 1988

Five nematophagous fungi were evaluated for their nematicidal effect in vitro on Rhabditis sp. and Meloidogyne hapla in soil. Inocula of Arthrobotrys arthrobotryoides, A. conoides, A. oligospora, Dactylella lobata, and Fusarium oxyaporum were grown in moistened corn-sandy soil and chopped potato-sandy soil media, and incubated at 26$^{\circ}C$ for one week. The prepared inocula were incorporated in autoclaved sandy soil, mixing thoroughly at rates equ-invalent to 1:50, 1:100, 1:200, and 1:400, repectively, before 80g of the mixture carrying 100 Rhabditis sp. was put into petri plates. Nematophagous fungi effectively teduced the popuation of Rhabditis sp. in soil in a week or two following treatment of the incula at concentration of 1:50 and 1:100. The optimum was at $25^{\circ}C$ for nematicidial effect as high as 80-100%. The at the rate of 1:100 prepared incula were incorporated in auto-claved soil, where 100 Juveniles M. hapla were introduced per 80% soil. All fungi infected the M. hapla effectively in soil, caysing more than 90% mortality within one week. This result indicated the potential value of these fungi as promising biocontrol agents.

• Journal of Radiation Industry
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• v.8 no.2
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• pp.97-104
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• 2014

Postharvest diseases cause considerable losses to harvested fruits and vegetables worldwide. Fresh produce suspected of harboring postharvest disease must be treated to control any pathogens present. Although there are various treatments to control postharvest losses by pathogens, the current community is eager to take safer and more eco-friendly alternatives to help with human health and reduce environmental risks. Ionizing irradiation is a promising phytosanitary treatment that has a significant potential to control postharvest diseases in use worldwide. Although almost 19000 metric tons of sweet potatoes and various fruits are irradiated each year in six countries to control postharvest disease, irradiation continues to be a debate, with slow acceptance by industries. Irradiation alone is not effective as a fungicide, and an over dose affects the physical properties of irradiated products. A combination of irradiation with other treatments such as heating, biocontrol agents, chlorination, and nano Ag particles is to enhance their effectiveness. Challenges to the use of phytosanitary irradiation are an avoidance of irradiated postharvest and cost of the irradiation facilities, and thus consumers still need to be educated on the principles and benefits of irradiation and prepare an optimum economy of scale for commercial use. In this review, we evaluated the current phytosanitary irradiation, and combination with various other treatments to minimize the postharvest losses.

• Research in Plant Disease
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• v.30 no.1
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• pp.66-77
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• 2024

Black wood ear mushroom (Auricularia auricula-judae) is one of the most economically important mushrooms in China, Japan, and Korea. The cultivation of wood ear mushrooms on artificial substrates is more efficient in terms of time and cost compared with their natural growth on trees. However, if the substrate cultivation is infected by fast-growing fungi, the relatively slow-growing ear mushroom will be outcompeted, leading to economic losses. In this study, we investigated the competitive fungal isolates from substrates infected with fast-growing fungi for the cultivation of ear mushrooms in Jangheung and Sunchon, Korea. We collected 54 isolates and identified them by sequencing their internal transcribed spacer region with morphological identification. Among the isolates, the dominant isolates were Trichoderma spp. (92.6%), Penicillium spp. (5.6%), and Talaromyces sp. (1.8%). To find an appropriate eco-friendly biocontrol agent, we used five Streptomyces spp. and Benomyl, as controls against Trichoderma spp. and Penicillium spp. Among the six Streptomyces spp., Streptomyces sp. JC203-3 effectively controlled the fungi Trichoderma spp. and Penicillium spp., which pose a significant problem for the substrates of black wood ear mushrooms. This result indicated that this Streptomyces sp. JC203-3 can be used as biocontrol agents to protect against Trichoderma and Penicillium spp.

• Research in Plant Disease
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• v.15 no.3
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• pp.230-235
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• 2009

Postharvest skin sooty dapple and decay disease of pear fruit often originates at small stain symptoms that occurred during harvest and handling. Experiments were conducted to characterize the effect of timing of application of disease control materials, and to evaluate sequential postharvest applications of fungicides or fungicides and bio-control agents. Fungicides and bio-control agents were increasingly less effective when the period between harvest and application was prolonged. Thiabendazole (TBZ) applied to fruit without artificial wounding or inoculation effectively reduced skin sooty and decay disease when applied within 3 weeks or 6 weeks in 2 years of study. TBZ, Fludioxonil and pyrimethanil were effective in controlling skin sooty and decay disease at artificial wounds inoculated with Cladosporium tenuissimum up to 14 days after inoculation. Application of TBZ at harvest followed 3 weeks later by application of Fludioxonil was superior to application of TBZ at harvest alone. Two bacterial biocontrol agents reduced skin sooty and decay disease at pear wounds inoculated with C. tenuissimum up to 14 days after inoculation with C. tenuissimum, but were ineffective when applied at 28 days after inoculation. Of possible sequential arrangements of fungicide and bio-control treatments, application of the most effective material promptly after harvest generally resulted in the highest level of disease control.

• The Korean Journal of Pesticide Science
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• v.18 no.4
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• pp.396-403
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• 2014

Ginseng (Panax ginseng C. A. Meyer) is an economically valuable pharmaceutical crop in Korea. In order to find promising biocontrol agents for soil-borne fungal pathogens which infect ginseng roots, we have isolated actinomycete, BK185 from soil. The isolate was investigated for the antifungal activity against to ginseng rot pathogens prior to testing genetic and chemical properties. The strain was identified as Streptomyces sp. using phylogenetic analysis based on 16S rRNA gene sequence. The most closely related species was S. sporoclivatus and S. geldanamycininus with high similarities (>99%). The isolate, BK185 showed positive reaction for PCR detection targeting biosynthetic gene clusters of PKS (Type-I polyketide synthase) and NRPS (Non-ribosomal polypeptide synthetase) genes. Major metabolite from the BK185 was analyzed by The LC/MS and identified to geldamycin, which was known to contained broad antibacterial, antifungal or anticancer activities. The results provide evidences that the strain, BK185 can be promising biocontrol agent for ginseng organic farming.

• The Korean Journal of Pesticide Science
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• v.21 no.1
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• pp.90-96
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• 2017

Gray mold disease, cause by Botrytis cinerea, occurs severe damage on varieties of fruit and vegetable production, and have no a critical control method. In case of chemicals control, it is a trigger emergence of drug resistance strains due to using them continuously. In addition, the pathogen is difficult to control naturally because it is possible to survive regardless of host status. In this study, microorganisms were isolated from tomato flower and hive samples and in order to select suitable microbial control agents for tomato gray mold disease. During six-months study, we isolated 1,004 isolates from flower and 925 isolates from pollinator hive samples. Among them, 6 strains were selected based on result of antifungal activity test. The selected strains showed not only strong antifungal activity against gray mold pathogen, but also cellulase and protease enzyme activities. The selected strains were identified as Paenibacillus polymyxa. In plant assay, P. polymyxa prevented the gray mold disease occurrence near 75%.