• Korean Journal Plant Pathology
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• v.13 no.2
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• pp.95-99
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• 1997

To obtain a basic information of breeding for resistance to clubroot in Chinese cabbage, disease incidence, pathogenicity, and varietal response to the pathogen were studied. Incidence of clubroot was observed at 3 districts in Gyeonggi-Do, 2 districts in Kangwon-Do, and 1 district each in Gyeongnam, Geongbuk and Jeonbuk, respectively. Disease infection rate and diseased ara were most severe in northern part of Gyeonggi-Do. The isolates of clubroot collected from 8 different districts were not different in their virulence one another in view of their infection rate and disease severity in Chinese cabbage. The clubroot fungus had a wide host range for the cruciferous vegetables. Disease severity was high in rape, turnip and mustard, moderate in Chinese cabbage and broccoli, and low in kale and cauliflower. All of Korean hybrids of Chinese cabbage tested were highly susceptible to clubroot, but Japanese varieties were resistant to the highly pathogenic isolate (EJ-93) which was isolated from the Chinese cabbage in Korea. The hybrid(F1) between clubroot resistant line(930WG) and the susceptible line(332MS) showed completely resistant reaction, which indicated that clubroot resistance was governed by a dominant gene.

• Korean Journal of Agricultural Science
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• v.38 no.4
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• pp.613-618
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• 2011

To develop clubroot resistant Chinese cabbage inbreds, IT 033820, a clubroot resistant turnip, was cross pollinated with a Chinese cabbage inbred of BP 079. From 2005, conventional breeding and microspore culture method performed using these F1 plants as parental materials. In 2007, conventional breeding method resulted in 21 F3 inbreds. After inoculation of clubroot race 4, one inbred showing 83% resistant was selected and registered as 'onkyo 20036ho' in 2008. From 2005, we scanned hybrid cultivars using micro spore culture and developed many doubled haploid (DH) lines in Chinese cabbage. Using Chinese cultivar of 'oong-baek 2ho' we developed 26 DH inbreds in 2007. After inoculation of clubroot race 4, one DH inbred showing 77% resistant and yellow inner leaf color was selected and registered as 'onkyo 20034'in 2008. We found conventional breeding method was effective using introduced germplasm showing low germination. However, when using hybrid cultivar as starting material, microspore culture method was powerful for developing various inbred in short time.

• Research in Plant Disease
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• v.14 no.2
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• pp.85-89
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• 2008

Clubroot of Chinese cabbage, caused by Plasmodiophora brassicae, is one of the most serious plant diseases in the world. The objectives of this study were to investigate the effect of the irrigation times on the development of club root after planting and to evaluate the effect of clubroot disease on yield of chinese cabbage in pot and field. The clubroot disease gradually increased with increasing irrigation frequency after planting. The growth characters and yield of chinese cabbage by irrigation times varied according to soil moisture and clubroot disease severity. Based on marketable yield and control value, an ideal irrigation point was at the soil matric potential of 0.06 MPa. These results suggest that the suppression on clubroot disease development could be achieved by initially reduced irrigation times after planting. Future studies on irrigation times using fungicide treatment and resistant cultivar under natural field conditions are required to improve the control effect of clubroot.

• Plant Disease and Agriculture
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• v.5 no.2
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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.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.433-441
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• 2016

Clubroot caused by the protist Plasmodiophora brassicae is one of the most destructive diseases of Brassica crops. Developing Chinese cabbage cultivars with durable clubroot resistance (CR) is an important goal of breeding programs, which will require new genetic resources to be identified and introduced. In this study, we evaluated resistance to P. brassicae race 4 using 26 Chinese cabbage (B. rapa ssp. pekinensis ) cultivars compared to the clubroot-susceptible Chinese cabbage inbred line 'BP079' and the clubroot-resistant European turnip (B. rapa ssp. rapifera ) inbred line 'IT033820'. No symptoms of clubroot disease were found in 'IT033820' infected with P. brassicae race 4, whereas the Chinese cabbage cultivars exhibited disease symptoms to various degrees. The Chinese cabbage cultivars that were reported to be clubroot-susceptible were susceptible to P. brassicae race 4; however, seven of the 20 cultivars reported to be clubroot-resistant were susceptible to this race of P. brassicae to varying degrees. Resting spores of P. brassicae were abundant within the infected root tissues of 'BP079', as revealed by light microscopy and scanning electron microscopy (SEM), but they were not detected in root tissues of 'IT033820'. Although resting spores were not detected by light microscopy in root tissues of the clubroot-resistant Chinese cabbage cultivar 'Kigokoro 75', a few spores were observed by SEM. The $F_1$ hybrids from a cross between 'IT033820' and 'BP079' showed no disease symptoms, and all $BC_1P_1$ progenies from a cross between the $F_1$ hybrid and 'IT033820' exhibited a resistance phenotype. In the $BC_1P_2$ population from a cross between the $F_1$ hybrid and 'BP079', this trait segregated at a ratio of 3(R):1(S) (${\chi}^2=1.333$, p = 0.248) at a 5% significance level. Inoculated $BC_1P_2$ plants were either highly resistant or highly susceptible to the pathogen, indicating that the CR to race 4 of P. brassicae carried by 'IT033820' is dominant. In the $F_2$ population, this trait segregated at a ratio of 15(R):1(S) (${\chi}^2=0.152$, p = 0.696) at a 5% significance level, suggesting that CR in 'IT033820' is mainly controlled by two dominant genes. Therefore, 'IT033820' represents a promising genetic resource for developing durable CR breeding lines in Chinese cabbage.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.50-50
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• 2015

Both agriculture and local tourism of Kagoshima prefecture where is located on the south-western region of the Japanese mainland, are the important industries. Although cabbage (Brassica oleracea) has been cultivated in recent decades in Kagoshima, clubroot disease caused by Plasmodiophora brassicae had never been observed. However, the disease in cabbage was reported in four regions last couple years. Our survey showed that one region is infested severely whereas others are slightly. In the most widely infested region, the disease was also observed in turnip rape (Brassica rapa) which is grown as ornamental plants for landscape design in early spring and important tourist attraction. Consequently, both agriculture and local tourism are damaged by clubroot. The increase of clubroot incidence in this region might be caused by significant increase of cabbage production, the expansion of cropping season throughout the year and continuous turnip rape cultivation in the same fields of cabbage for almost three decades. Therefore we are trying to estimate the risk of clubroot damage cultivation throughout the year in this region. We collected five isolates of resting spores and identified them as race 3, 4 and 9 by Williams' method, and as pathotype group 3 and 4 by classification system using clubroot resistant (CR) $F_1$ cultivars of Chinese cabbage as differential hosts as described in Hatakeyama et al.(2004). Furthermore, we found that these populations were avirulent to commercial CR cabbages. These results indicate that introduction of CR cabbage and breeding of turnip rape are the effective measures to solve our problem.

• The Plant Pathology Journal
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• v.32 no.5
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• pp.423-430
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• 2016

Clubroot disease caused by Plasmodiophora brassicae is one of the most serious diseases in Brassica crops worldwide. In this study, the pathotypes of 12 Korean P. brassicae field isolates were determined using various Chinese cabbage including 22 commercial cultivars from Korea, China, and Japan, and 15 inbred lines. All P. brassicae isolates exhibited the typical clubroot disease on non-clubroot resistant cultivar, indicating that the isolates were highly pathogenic. According to the reactions on the Williams' hosts, the 12 field isolates were initially classified into five races. However, when these isolates were inoculated onto clubroot-resistant (CR) cultivars of Chinese cabbage, several isolates led to different disease responses even though the isolates have been assigned to the same race by the Williams' host responses. Based on the pathogenicity results, the 12 field isolates were reclassified into four different groups: pathotype 1 (GN1, GN2, GS, JS, and HS), 2 (DJ and KS), 3 (HN1, PC, and YC), and 4 (HN2 and SS). In addition, the CR cultivars from Korea, China, and Japan exhibited distinguishable disease responses to the P. brassicae isolates, suggesting that the 22 cultivars used in this study, including the non-CR cultivars, are classified into four different host groups based on their disease resistance. Combining these findings, the four differential hosts of Chinese cabbage and four pathotype groups of P. brassicae might provide an efficient screening system for resistant cultivars and a new foundation of breeding strategies for CR Chinese cabbage.

• 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.

• Research in Plant Disease
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• v.16 no.1
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• pp.59-65
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• 2010

This study was conducted to select the cultivars and strains which are suitable in cultivation of the Chinese cabbage having good horticultural characteristics and the resistance to clubroot caused by Plasmodiophora brassicae, which is a widespread disease that causes serious problems in many Brassica growing areas. Thirty four cultivars and nineteen strains of the Chinese cabbage were planted in the contaminated fields in highland and investigated the wilting symptom due to the initial disease occurrence and high temperature. Disease occurrence rate and severity of clubroot and the horticultural characteristics were also examined. According to the results, Bulamplus, Kangryeokyeoleumbaechu among cultivars of Chinese cabbage, SP-05, SP-02, CR DB 50, and CR DB 29 among strains of Chinese cabbage were resistant to hot weather by showing delayed above-ground symptom (wilting) of clubroot in 30 days after transplanting. In case of below-ground clubroot rate, Daetong, super CR Kimi 85 and super CR Hiroki among the cultivars of Chinese cabbage were resistant to clubroot in 60 days after transplanting. When fresh weight of Chinese cabbage among cultivars were compared, super CR Hiroki of over 2,500 g was the highest among other cultivars. Although the resistant and susceptible reactions of Chinese cabbage cultivars and strains against clubroot disease were somewhat different from the above-ground symptoms (wilting) of clubroot in 30 days and below-ground symptoms of clubroot in 60 days, we recommend that super CR Hiroki, CR Kimi 85, CR Janggun among cultivars of Chinese cabbage and CR DB 50 and CR DB 29 among strains of Chinese cabbage will be more suitable in cultivation of Chinese cabbage in highland.

• 한국균학회소식:학술대회논문집
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• 2015.05a
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• pp.37-37
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• 2015

Kimchi cabbage (Chinese cabbage), radish and Cabbage are major Brassicaceae vegetables in Korea. Especially, we can easily develop whole plant from one microspore in Kimchi cabbage. To develop clubroot resistant doubled-haploid (DH) inbred lines, we pollinated a clubroot resistant turnip of 'IT 033820' with a Kimchi cabbage (Chinese cabbage) inbred of 'BP 079'. More than 85 DH inbred lines were developed from this combination. We screened about 400 materials including these DH inbred lines, commercial cultivars and breeding materials during 3 years using hydroponic system after inoculating single spore isolation race 4(SSI-04) inoculate. One inbred line derived from this combination selected as clubroot resistant and registered as 'Wonkyo20036ho'. We inoculated 26 DH inbred lines derived from 'Zoong-baek 2ho' using SSI-4, the percent of resistant plants varied from 0 to 83%. However the horticultural traits of highly resistant DH inbred line was poor. Thus we selected one DH line showing 77% resistant with yellow inner leaf and maid good head, was registered as 'Wonkyo20034ho'. Another DH inbred line derived from Korean variety of 'Wol-dong' showing 86% resistant was registered as 'Wonkyo20037ho'. Other DH inbred lines were derived from Chinese cultivar of 'Choon-hi-go-hang-wang' and 'Hwang-shim-zo48' showed 80 and 71% resistant, respectively, was also selected for registration. Even though DH inbred lines derived from turnip showed highly resistant to SSI-04 and provincial inoculate, they showed poor characteristics in horticultural traits. However, commercial seed companies showed interesting for adapting these DH inbred lines in commercial breeding.