• 식물병과 농업
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• 제5권2호
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• pp.90-94
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• 1999

Effect of inoculum concentration inoculation method and plant age on development of clubroot disease of Chinese cabbage seedling were examined in growth chambers. Root galls were developed at the concentration of 105 resting spore or above per ml of incoulum and as the inoculum concentration became higher rate of development of root galls was faster. In the plants with root gall development fresh weight of above ground parts was reduced to 30-44% of that of healthy plants but root weight increased by 4-10 times. Growth of diseased plants was greatly reduced as compared to healthy plants. Planting in the diseased soil as a inoculation method was most effective for disease development showing uniform infections but time of initial root gall development was delayed by root soaking inoculation. Some plants inoculated by soil drenching method did not develop root galls. However root gall enlargement after its initial formation did not differ greatly among inoculation methods. Nine-day-old seedlings showed poor development of root gall but 16-days-old seedlings was found to be most adequate for inoculation for gall development.

• 한국균학회지
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• 제43권4호
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• pp.286-289
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• 2015

순활물기생체인 Plasmodiophora brassicae는 병원성 검정을 위해서 반드시 뿌리혹을 장기적으로 보관하는 것이 매우 중요하기 때문에 그동안 병원성을 유지하는 것이 관건이다. 특히 기존의 방법은 100년 이상 사용되어온 저장법으로 개선이 필요하여 그 효율적인 방법을 밝히고자 하였다. 이 결과 장기적으로 병원성의 저하를 최소화하며 장기간 뿌리혹을 저장할 수 있는 방법은 $-70^{\circ}C$ 냉동고에 보관하는 것으로 확인되었고, 저장 조건은 뿌리혹을 그대로 보관하거나 뿌리혹을 갈아 균질화한 후 여러 겹의 거즈에 거른 것이 6가지 저장조건 중에 가장 효과적인 저장법으로 밝혀졌다.

• 식물병과 농업
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• 제5권2호
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• pp.84-89
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• 1999

Development of root galls of clubroot disease on Chinese cabbage seedlings was first observed 17days after inoculation of Plasmodiophora brassicae at $25^{\circ}C$ 4-11days earlier than at 5, 20, 3$0^{\circ}C$ and 35$^{\circ}C$. Subsequent enlargement of root galls was also fastest at $25^{\circ}C$ and 2$0^{\circ}C$ but delayed at 15$^{\circ}C$ and 3$0^{\circ}C$ or above. Chinese cabbage seedlings with root gall formation showed reduction in number of leaves above ground fresh weight and amount of root hairs but increase in root weight, Root galls development was highest at soil moisture level of 80% of maximum soil moisture capacity than at 60% and 100%. Optimum soil pH for root gall development was pH 6 although root galls were formed at a range of pH 5 to 8. Period of light illumination also affected root gall development with the greatest gall development at 12hr/12hr in light/dark period and the least at 8hr/16hr. Site of root gall formation and gall shape did not differ greatly among treatments of temperature soil moisture pH and light experiments.

• 식물병과 농업
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• 제5권2호
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• pp.77-83
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• 1999

In 1997 surveys 82 out of 180 crucifer fields were infected with clubroot disease in a range of 1-100% of diseased plants and among crucifier crops Chinese cabbage was the most severe, In cropping systems Chinese cabbage-monocropping of Chinese cabbage-radish were found to be most common in major Chinese cabbage production areas. Welsh onion squash or paddy rice were also planted between cropping of Chinese cabbage. Paddy fields converted to upland were lowered in incidence of clubroot disease and fields with loam to silty loam soil were more severe in disease than those with sandy soil. Soil pH and organic contents were nor related to clubroot disease severity. Soil fauua such as total fungi bacteria actinomyces Pseudomonads and Bascillus were not correlated with severity of the disease. Root rall development on Chinese cabbage seedlings was initifially observed under a microscope 13 days after inoculation with Plasmodiophora brassicae but 18 days by naked eyes after inoculation. Root galls were formed mostly around collar roots and gradually spread to main root lateral roots and secondary root branches. Root galls started to enlarge greatly in size and weight from 23 days after inoculation. Chinese cabbage plants at mid-growth stage with root gall development were reduced to 1/2 of that of healthy plants in number of leaves 1/4-1/5 in above ground fresh weight 1/6 in root length but increased to 3 times in diameter of collar root. Diseased plants had little root hairs. Diseased Chinese cabbage plants at harvest were reduced by 9,1-11.8% in head weight compared to healthy plants a positive correlation was observed between root and head weight but those relationships were rot found in the diseased plants.

• Mycobiology
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• 제39권3호
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• pp.233-234
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• 2011

Clubroot symptoms were frequently observed on roots of shepherd's-purse (Capsella bursa-pastoris) grown in a field in Nonsan, Chungnam province, Korea in March, 2009. Many resting spores were found in the cells of the root gall tissues collected from the field. The clubroot pathogen was identified as Plasmodiophora brassicae based on its morphological and pathological characteristics. This is the first report that P. brassicae causes clubroot of shepherd's-purse in Korea.

• Mycobiology
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• 제37권1호
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• pp.69-71
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• 2009

Clubroot symptoms occurred severely on roots of Pak-Choi (Brassica campestris ssp. chinensis) grown in greenhouses in Gwangju city, Gyeonggi province, Korea in September, 2008. The incidence of the disease symptoms reached as high as 90% in three greenhouses investigated. The root galls collected from the greenhouses were sectioned using a scalpel and observed by light microscope. Many resting spores were found in the cells of the root gall tissues. Suspension of resting spores was prepared from the root galls and inoculated to roots of healthy Pak-Choi plants. Each of five resting spore suspensions caused clubroot symptoms on the roots, which were similar to those observed during the greenhouse survey. Resting spores of the pathogen were observed in the cells of the affected roots. The clubroot pathogen was identified as Plasmodiophora brassicae based on its morphological and pathological characteristics. This is the first report that Plasmodiophora brassicae causes clubroot of Pak-Choi.

• 한국균학회지
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• 제48권4호
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• pp.499-503
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• 2020

Clubroot symptoms were frequently observed on the roots of Baecheongchae plants grown in vinyl greenhouses of a farmer located in Yangpyeong area of Korea during a disease survey in June 2019. The incidence of diseased Baecheongchae plants ranged from 30 to 90% in the vinyl greenhouses investigated. Many resting spores were found in the tissue of root galls collected. The resting spores were hyaline and spherical and measured 2.5-4.2 ㎛ in diameter. Three inoculum suspensions of resting spores prepared from the root galls were inoculated to the roots of healthy Baecheongchae plants. All the inoculum suspensions caused clubroot symptoms to appear on the roots of the inoculated Baecheongchae plants. The symptoms on the roots induced by artificial inoculation were similar to those observed in the plants of the vinyl greenhouses during the disease survey. Resting spores of the pathogen were recovered from the root galls of the inoculated plants. Three root gall isolates obtained from the inoculated plants were used for molecular identification. Comparing the isolates to the Plasmodiophora brassicae strains in GenBank, the amplification products demonstrated 100% similarity with the internal transcribed spacer (ITS2) sequences. The clubroot pathogen was identified as P. brassicae according to its morphological, pathological, and molecular characteristics. This is the first report of P. brassicae causing clubroot in Baecheongchae.

• 한국균학회소식:학술대회논문집
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• 한국균학회 2015년도 춘계학술대회 및 임시총회
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• pp.27-27
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• 2015

Clubroot (Plasmodiophora brassicae) is a serious agricultural problem affecting Brassica crop production worldwide. It also infects the model plant Arabidopsis thaliana. During infection, this biotrophic pathogen manipulates the development and metabolism of its host leading to the development of galls in the root and hypocotyl. In turn, its own development is strongly influenced by the host. The aim of this study is to investigate the metabolism of clubroot-infected plants using a combination of transcriptomic and metabolomic approaches. We have used direct injection mass spectrometry to obtain a metabolic fingerprint of when changes in the metabolome occur and linked this with changes in host and pathogen gene expression. We have identified alterations in carbohydrate metabolism that occur during P. brassicae infection of A. thaliana plants. Transcriptomic analysis showed that host genes associated with sugar transport and metabolism were induced during gall formation and that the pathogen also expresses genes associated with these processes. We have examined the impact of inactivating host sucrose synthase, cytosolic invertase and sugar permeases on gall formation, identifying host genes that are required for gall formation. We have also explored how sugar status is changed in root tissue, developing and mature leaf during infection of wild type and mutant plants.

• 식물병연구
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• 제6권1호
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• pp.23-26
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• 2000

봄배추 무사마귀병의 감염시기별 피해정도를 포장시험으로 조사하였다. 정식후 감염시기가 빠를수록 수량에 대한 피해가 컸으며 정식후 20일 이전 감염배추는 수확전 완전히 고사하였고 정식후 30일에 감염된 배추는 수확시까지 외관상 건전한 생육을 보였으나 포기무게가 건전주의 59%에 불과하여 상품성이 없었다. 정식 40일 이후 감염배추는 수량에 대한 영향이 없었다. 이병배추는 감염후 시간이 경과할수록 잔뿌리의 생성이 감소되어 생육후기에는 거의 잔뿌리가 없었으며 뿌리의 신장도 건전주에 비해 1/2∼1/3 수준으로 감소하였다. 뿌리혹은 감염 20일후에 처음으로 관찰되어 이후 급속히 비대하였으며 최초 생성 20일후에 최대치에 달하였고 그후 혹뿌리의 부패로 근중이 감소하기 시작하여 수확기에는 건전주보다 낮아졌다. 뿌리혹의 발달 및 부패속도는 감염시기와 상관없이 배추생육기의 온도가 높아질수록 빨라지는 경향을 보였다. 식물체 위조는 뿌리혹이 생성된지 10일후에 처음으로 관찰되었으며 그후 10일경부터 혹이 부패하기 시작하여 열흘동안 완전히 부패 소실되었고 식물체도 고사하였다. 따라서 봄배추의 무사마귀병 포장정식시 감염은 20일간의 잠복기 20일간의 혹비대기를 거쳐 10일동안의 혹부패기, 그후의 토양내 잔존기로 구분이 가능하였다.

• 식물병연구
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• 제9권2호
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• pp.57-63
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• 2003

Clubroot disease of curcifer crops caused by Plasmodiophora brassicae had been first reported in 1928 in Korea, and maintained mild occurrence until 1980s. Since 1990s the disease has become severe in alpine areas of Kyonggi and Kangwon, gradually spread to plain fields throughout the country, and remains as the great-est limiting factor for its production. Researches on the disease has begun in late 1990s after experiencing severe epidemics. Survey of occurrence and etiological studies have been carried out, particularly, on the pathogen physiology, race identification, quantification of soil pathogen population, and host spectrum of the pathogen. Ecology of gall formation and its decay, yield loss assessment associated with time of infection, and relationships between crop rotation and the disease incidence was also studied during late 1990s. In studies of its control, more than 200 crucifer cultivars were evaluated for their resistance to the disease. Lime applica-tion to field soil was also attempted to reduce the disease incidence. Resistant radish and welsh onion were recommended as rotation crops with crucifers after 3-year field experiments. However, so for, most studies on clubroot disease in Korea have been focused on chemical control. Two fungicides, fluazinam and flusulfamide, were selected and extensively studied on their application technologies and combination effects with lime application or other soil treatment. To develop environmentally-friendly control methods, solar-disinfection of soil, phosphoric acid as a nontoxic compound, and root-parasiting endophytes as biocontrol agents were examined for their effects on the disease in fields. In the future, more researches are needed to be done on development of resistant varieties effective to several races of the pathogen, establishment of economically-sound crop rotation system, and improvement of soil-disinfection technique applicable to Korean field condi-tion, and development of methodology of pretreatment of fungicides onto seeds and seedbeds.