• Microbiology and Biotechnology Letters
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• v.32 no.2
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• pp.172-178
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• 2004

This research is performed for a biological control of Chinese cabbage clubroot, we isolated an antagonistic bacterium AC-3 against Plasmodiophora sp., causal pathogens of cabbage clubroot. The isolated strain was identified as Streptomyces sp. by culture morphology, biochemical reactions, and homology research based on l6S rDNA sequences. Streptomyces sp. AC-3 produced chitinase (9.3 units/$m\ell$) in culture broth. So Plasmodiophora sp. mycelia changed abnonnal swelling, curling and branching mycelia by Streptomyces sp. AC-3 culture. In a field infected by Plasmodiophora sp., the treatment of a organic fertilizer added 2% Streptomyces sp. AC-3 microbial inoculant, it resulted in about 50% reducing the severity of cabbage clubroot significantly on cabbage plants compared with treated organic fertilizer plants. Additional disease such as sclerotinia rot, fusarium wilt and pythium rot were also significantly reduced by the treatment of the organic fertilizer added Streptomyces sp. AC-3 microbial inoculant.

• The Korean Journal of Mycology
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• v.43 no.4
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• pp.286-289
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• 2015

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is a severe soilborne disease of Brassicaceae. Storage of clubroot gall is important for studies on pathogenicity and race identification. As the current storage method has been used for more than 100 years, a new storage method should be developed and the most efficient way maintaining pathogenicity should be determined. Effects of storage conditions with different storage periods on pathogenicity in galls of kimchi cabbage were examined in a greenhouse. The experiments were performed under six conditions and four temperatures in order to determine the most effective storage conditions for maintenance of pathogenicity. The most effective conditions for clubroot gall storage was the storage of whole gall at $-70^{\circ}C$ or storage of filtrate at the same temperature through eight layers of gauze after homogenization of the galls.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.70.2-70
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• 2002

• Journal of Microbiology and Biotechnology
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• v.23 no.3
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• pp.313-321
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• 2013

Bacillus subtilis XF-1, a strain with demonstrated ability to control clubroot disease caused by Plasmodiophora brassicae, was studied to elucidate its mechanism of antifungal activity against P. brassicae. Fengycin-type cyclopeptides (FTCPs), a well-known class of compounds with strong fungitoxic activity, were purified by acid precipitation, methanol extraction, and chromatographic separation. Eight homologs of fengycin, seven homologs of dehydroxyfengycin, and six unknown FTCPs were characterized with LC/ESI-MS, LC/ESI-MS/MS, and NMR. FTCPs (250 ${\mu}g/ml$) were used to treat the resting spores of P. brassicae ($10^7/ml$) by detecting leakage of the cytoplasm components and cell destruction. After 12 h treatment, the absorbencies at 260 nm ($A_{260}$) and at 280 nm ($A_{280}$) increased gradually to approaching the maximum of absorbance, accompanying the collapse of P. brassicae resting spores, and nearly no complete cells were observed at 24 h treatment. The results suggested that the cells could be cleaved by the FTCPs of B. subtilis XF-1, and the diversity of FTCPs was mainly attributed to a mechanism of clubroot disease biocontrol.

• Research in Plant Disease
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• v.25 no.1
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• pp.33-37
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• 2019

From 2016 to 2018, approximately 15% of kohlrabi were observed displaying significant clubroot symptoms in farmer's fields in Jeju, Korea. The initial infection appeared as hypertrophy of root hairs, and as the disease progressed, galls formation occurred on the main roots, finally disease progress resulted in yellowing and wilting of leaves. Pathogenicity was proven by artificial inoculation of plants with resting spore suspension, fulfilling Koch's postulates. The resting spore is one-celled, spherical and subspherical, colorless, and $3-5{\mu}m$ in diameter. On the basis of the morphological characteristics and phylogenetic analyses of internal transcribed spacer rDNA, the causal agent was identified as Plasmodiophora brassicae. To our knowledge, this is the first report on the occurrence of P. brassicae on kohlrabi in Korea.

• Research in Plant Disease
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• v.15 no.3
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• pp.242-247
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• 2009

To select rotation crops for control of clubroot of Chinese cabbage, potato, corn, soybean, onion and groundsel were planted in the field infected with clubroot pathogen (Plasmodiophora brassicae) in highland area in 2000. In comparison of economical efficiency among rotation crops, potato and onion gained about 16.9 and 14.9 times higher, respectively, than successive cultivation of Chinese cabbage. Resting spore densities of Plasmodiophora brassicae after harvesting rotation crops were in the range of $0.3{\sim}1.2{\times}10^3/g$ soil in all cultivated soils with rotation crops while that of successive Chinese cabbage cultivation soil was very high as much as $89.3{\times}10^3/g$ soil. And disease severity of Chinese cabbage clubroot was 4.9, 20.2, 24.4, 25.1 and 27.8% in onion, soybean, potato, corn, and groundsel cultivation plot, respectively, while that of successive Chinese cabbage cultivation plot was very high as 77.8%. Effect of rotation period of onion, potato, soybean on disease control was investigated from 2002 to 2005. Resting spore densities of Plasmodiophora brassicae after cultivating rotation crops were decreased until $2^{nd}$ year and maintained low density at $3^{rd}$ year in all plots, while that of successive Chinese cabbage cultivation plot was increased 2.6 to 23.6 times for three years. When Chinese cabbage was rotation-cultivated with potato, soybean and onion for three years, disease severities of Chinese cabbage clubroot decreased 92 to 4.4%, 72 to 10.4% and 72 to 12.2%, respectively, while that of successive Chinese cabbage cultivation plot maintained 100%. As the rotation period increased, the yields of Chinese cabbage increased, while that of successive Chinese cabbage cultivation plot decreased. At $3^{rd}$ year, Chinese cabbage with high quality could be much more produced 2,205, 2,493 and 2,476 g in potato, soybean and onion cultivation plot, respectively, than 95 g in successive Chinese cabbage cultivation plot.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.38-38
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• 2015

Throughout the world, clubroot disease is one of the most damaging diseases affecting Brassica oleracea. In order to perform QTL analysis of CR (clubroot resistance) loci in B. oleracea, we constructed a map, and analyzed CR-QTLs using the mean phenotypes of F3 progenies from the cross of a resistant double-haploid cabbage line (Anju) with a susceptible double-haploid broccoli line (GC). We identified one major QTL, pb-Bo(Anju)1 in C2 from Anju and four minor QTLs; pb-Bo(GC)1 in O5 from GC, pb-Bo(Anju)2, -3, -4 in C2, C3, and C7 from Anju, respectively. Additionally, we found that the accumulation of Pb-Bo(Anju)1 allele and the minor CR-QTLs is essential for resistance against various six isolates. Our finding markers closely linked to the CR-QTLs will help marker-assisted selection for CR. At present, we are undergoing toward map-based cloning for Pb-Bo(Anju)1 gene. The preliminary experiment delimited Pb-Bo(Anju)1 locus, encompassing among 450kB.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.42-42
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• 2015

Plasmodiophora brassicae, the causal agent of clubroot disease, does the most serious damage to the Brassica crops. The limited control approaches make that the identification of clubroot resistance (CR) is more important for developing CR cultivars of the Brassica crops. So far, 8 CR loci were mapped. However, the variation of P. brassicae leads to the rapid erosion of its resistance. To identify novel CR genes, we employed three mapping population, derived from crosses between Chinese cabbage and turnip inbred lines ($59-1{\times}ECD04$ and $BJN3-1{\times}Siloga$) or between Chinese cabbage inbred lines ($BJN3-1{\times}85-I-II$), to perform QTL analysis. Totally, 8 CR loci were indentified and showed race-specific resistance. Physical mapping of these 8 loci suggested that 4 were located previously mapped position, indicating they might be the same allele or different alleles of the same genes. Other 4 loci were found to be novel. Further, CR near isogenic line carrying each CR locus was developed based on the marker assisted selection. Verification of these CR loci was underway. Identification of these novel CR genes would facilitate to breed broad-spectrum and durable CR cultivars of B. rapa by pyramiding strategies.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.33-33
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• 2015

Clubroot disease is the major threat to the production of Chinese cabbage (Brassica rapa L.) in Japan. Although the breeding of the clubtoot resistant (CR) cultivars is one of the most efficient ways to control this disease, the CR cultivars do not always have effects due to the breakdown of resistance. Therefore, it is necessary to develop the breeding strategy to accumulate multiple CR genes in a single cultivar effectively. We have identified two incomplete dominant CR loci, Crr1 and Crr2, which are originated from the European CR turnip Siloga. To investigate the effectiveness of marker-assisted selection (MAS) for CR breeding, the inbred line with Crr1 and Crr2 was crossed with parental lines of the existing CR $F_1$ cultivar of Chinese cabbage, followed by 5 times of MAS and backcrossing. The $F_1$ derived from a cross between the resulting parental lines improved the clubroot resistance as expected and had the same morphological characters as the original $F_1$ cultivar. We have shown that the Crr1 locus comprised two loci: Crr1a, which by itself conferred resistance to the mild isolate; and Crr1b, which had a minor effect, but was not required for Crr1a-mediated resistance. Further genetic analysis suggested that Crr1b was necessary to acquire resistance to the more virulent isolate in combination with Crr2. Molecular characterization of Crr1a encoding TIR-NB-LRR class of R protein revealed that there were at least 4 alleles in Japanese CR cultivars of Chinese cabbage. PCR analysis with Crr1a-specific markers demonstrated that the functional alleles were predicted to be present in European CR turnips, Debra and 77b besides Siloga, whereas rarely in Japanese CR cultivars, indicating that Crr1a is an useful source to improve the resistance of Chinese cabbage cultivars.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.12-12
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• 2002