Jeong Young Song

Direct Detection of Cylindrocarpon destructans, Root Rot Pathogen of Ginseng by Nested PCR from Soil Samples.

Abstract We have successfully applied the nested PCR to detect Cylindrocarpon destructans, a major pathogen causing root rot disease from ginseng seedlings in our former study. The PCR assay, in this study, was used to detect the pathogen from soils. The nested PCR using internal transcribed spacer (ITS) 1, 4 primer set and Dest 1, 4 primer set maintained the specificity in soils containing various microorganisms. For a soil DNA extraction method targeting chlamydospores, when several cell wall disrupting methods were tested, the combination of lyophilization and grinding with glass beads, which broke almost all the chlamydospores, was the strongest. The DNA extraction method which was completed based on the above was simple and time-saving because of exclusion of unnecessary stages, and efficient to apply in soils. As three ginseng fields whose histories were known were analyzed, the PCR assay resulted as our expectation derived from the field information. The direct PCR method will be utilized as a reliable and rapid tool for detecting and monitoring C. destructans in ginseng fields.

Environment Friendly Control of Gray Mold, a Ginseng Storage Disease Using Essential Oils

The objective of this study was to find an environment friendly method of ginseng storage disease control using a natural plant extract. Essential oil was evaluated in terms of its antifungal ability against a variety of ginseng storage pathogens, and a variety of essential oils was conducted in order to assess the possibility of applying them as a component of a disease control strategy. Direct treatment with essential oil was demonstrated to exert a ginseng storage control effect. Methyl eugenol and thymol were shown to exert a mycelial growth inhibition effect of 80% on PDA media, using a paper disc containing 200 ppm of essential oil against Botrytis cinerea. The application of direct methyl eugenol treatment to ginseng resulted in a profound control effect. Both spray and dipping treatment of each methyl eugenol as well as thymol, evidenced a disease develoment of 10-20% as compared with the over 80% observed from all non-treated packages. Methyl eugenol in the large packages resulted in a disease index of 0.60 in the two essential oil treatments and also a small diseased area, as compared with the disease index of 1.65 and the wide diseased area observed in the non-treatment groups. Treatment with a mixture (methyl eugenol + thymol) in the synergistic effect test resulted in a relatively wide diseased area, as no discernable synergistic effect was detected. Methyl eugenol and thymol can be utilized as control agents in an environmentally friendly ginseng storage treatment, owing to the avirulent and clear effects detected in this study. In particular, ginseng must be ingested when fresh, and this is why a product for the control of ginseng storage diseases is so necessary.

Genetic Characteristics of Acidovorax citrulli Population Causing Bacterial Fruit Blotch against Cucurbits in Korea

Jeong Young Song, Su Yeon Park, Mun Won Seo, Myeong Hyeon Nam, Hyoun Sub Lim, Seong-Chan Lee, Youn Su Lee and Hong Gi Kim* Department of Applied Biology, Chungnam National University, Daejeon 305-764, Korea Nonsan Strawberry Experiment Station, Chungcheongnam-do Agricultural Research & Extension Services, Nonsan 320-862, Korea Protected Horticulture Research Institute, National Institute of Horticultural and Herbal Science, Haman 637-812, Korea Division of Bio-resource Sciences, Kangwon National University, Chuncheon 200-701, Korea

Development of Species-Specific Primers for Plasmodiophora brassicae, Clubroot Pathogen of Kimchi Cabbage

Clubroot caused by the obligate biotrophic protist Plasmodiophora brassicae Woronin is one of the most damaging diseases of Brassicaceae family. In this study, we developed species-specific primer sets for rapid and accurate detection of P. brassicae. The primer sets developed amplified a specific fragment only from P. brassicae DNA while they did not amplify a band from 10 other soilborne pathogens or from Kimchi cabbage. In sensitivity test, the species-specific primer set ITS1-1/ITS1-2 could work for approximately 10 spores/ml of genomic DNA showing more sensitivity and accuracy than previous methods. With quantitative real-time PCR test, the primer set detected less spores of P. brassicae than before, confirming that the species-specific primer set could be useful for rapid and accurate detection of P. brassicae.

Genetic Diversity of Korean Cylindrocarpon destructans Based on Virulence Aassay and RAPD Analysis

Keumsan Ginseng & Medicinal Crop Experiment Station, Keumsan 312-822, Korea(Received 15, March 2011., Accepted 19, March 2011)ABSTRACT : Ginseng root rot caused by Cylindrocarpon destructans is one of the most destructive diseases of ginseng(Panax ginseng). We analyzed the features of the species through pathogenicity test and genetic diversity analysisof C. destructans in Korea, for its application as basic data to attempt for effective control. C. destructans isolatedfrom rotted ginseng roots exhibited a variety of colonial colors on media. It was assumed that there may existgenetic diversity in the population by the diversity of pathogenicity among isolates observed when artificially inoculatedinto ginseng roots. Pathogenicity tests using ex vivo wound inoculation with agar mixture inoculation on ginsengroots were performed similar results as were observed appear to be useful for rapid pathogen inspection. Accordingto RAPD analysis results, Korean C. destructans isolates formed a single genetic group which can be distinguishedreadily from closely related other fungi. C. destructans group was divided into two small groups. Therefore, wewere able to confirm pathogenicity and genetic difference between the isolates in each of the groups of the pathogen.KEYWORDS : Cylindrocarpon destructans, Genetic diversity, Ginseng root rot, Pathogenicity test, RAPD analysis

Chinese Cabbage Clubroot Pathogen, Plasmodiophora brassicae, Is Genetically Stable.

Abstract Single spore isolates of Plasmodiophora brassicae e4 and e9 obtained from diseased Chinese cabbage were identified as race 4 and race 9, respectively, by the Williams’ differential variety set. To confirm the possibility of variation in same generation and progeny of a single spore isolate of P. brassicae, random amplified polymorphic DNA (RAPD) analysis was conducted using the URP 3, 6 and OPA 7 primers. There was no difference in band type at each part of the gall of Chinese cabbage obtained by inoculation of e4 and e9 and amplification using the URP 3 and 6 primers when the same generation was analyzed. In addition, the progeny analysis, which was expanded to the third generation and conducted using the URP 3and OPA 7 primers, revealed no differences in the band type of the e4 isolate. Based on these results, the single spore isolate of P. brassicae was genetically stable.

Practical Application of Dioscorea quinqueloba Extract for the Control of Citrus Green Mold

This study tested the antifungal compound obtained from a medicinal plant, Dioscorea quinqueloba Thunb., in order to search the possibility of practical application of this product in agriculture through evaluating its activity using the citrus fruits. The extract of D. quinqueloba Thunb., which has the strongest antifungal activity, was selected as a candidate among 101 plant extracts. Based on this examination concerning antifungal activity of the product on Penicillium digitatum in vitro, it was confirmed its effect of mycelial growth inhibition showed over 87% at 0.5 mg/ml concentration. This natural product showed the stability of the substance, as it was not significantly influenced by pH, temperature, or ultraviolet radiation. While citrus fruits were stored at room temperature, P. digitatum was inoculated into them in order to prepare a similar environmental conditions with epidemic occurrence of the mold. As the result of our investigation, the disease preventive effects of the active antifungal substance evidenced a 100% at 0.5 mg/ml. When the phytotoxicity of the selected natural product on citrus at 2 mg/ml was assessed, we noted no toxic effects. Based on the superior preventive effects from this natural product extracted from the plant, it is presumed to be very useful in agricultural applications for the control of green mold, P. digitatum, which has been occurred often the biggest problem in the storage of citrus fruits.

Development of PCR Primers for Specific Identification and Detection of Botrytis cinerea on Tomato

Botrytis cinerea, gray mold pathogen, causes serious losses in greenhouse tomato crop. In this study, a primer set was developed for identification and specific PCR detection of B. cinerea from tomato plants. The primer pair (BTF1/BTR1) was designed from polymorphic sequence region in pyruvate carboxylase gene (pyc) of B. cinerea. A PCR product (112 bp) was amplified on genomic DNA of 13 B. cinerea isolates from 10 different host plants, but not on those from 6 other Botrytis spp., 4 Botryotinia spp., 5 Sclerotinia spp. and 16 other genus of phytopathogenic fungi. The sensitivity limit of the primer set was 2 pg of genomic DNA of B. cinerea, approximately. The PCR assay using species-specific primer set was specifically able to detect the pathogen on naturally infected tomato plants and artificially infected plants. These results suggest that the sensitivity and specificity of this primer set can be applied in a rapid and accurate diagnosis of tomato disease caused by B. cinerea.