• The Korean Journal of Pesticide Science
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• v.5 no.3
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• pp.50-53
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• 2001

Severe crown gall disease was occurred in green house cultivating rose in Jinchen, Chungbuk recently. Although it causes problem on rose cultivation, the growers do not have many choices of control measures for the disease now. Agrobacterium radiobacter K84 has been known as a strong antagonist against A. tumefaciens, a pathogen causing crown gall disease, and used as a biopesticide for crown gall in many countries since it had been introduced in 1972. We tested control activity of A. radiobacter K84 for the crown gall disease on rose. Spray of A. radiobacter K84 suspension on above ground of rose either before or after pathogen spray reduced size and fresh weight of galls significantly. Size and fresh weight of galls on roses inoculated with pathogen either before A. radiobacter K84 spray (pathogen-K84 treatment) or after A. radiobacter K84 spray(K84-pathogen treatment) were 4 to 5% of those of galls on roses inoculated pathogen only. Disease incidence of plants inoculated pathogen only was 85% whereas disease incidence of pathogen-K84 or K84-pathogen treatments were 6.7% and 5.0% respectively. Dipping of roots of rose in suspension of A. radiobacter K84 was also reduced size of galls and diseased rate significantly. These results indicate that A. radiobacter K84 is effective in the prevention of gall formation by A. tumefaciens and it can be used to control of crown gall disease of rose.

• Research in Plant Disease
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• v.16 no.3
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• pp.279-284
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• 2010

Clubroot caused by Plasmodiophora brassicae is a widespread disease that causes serious problems in many brassica growing areas. To establish more simple and reliable clubroot screening method of Chinese cabbage to P. brassicae using soil-drenching inoculation, the development of clubroot on Chinese cabbage according to several conditions such as soil type, inoculum concentration of P. brassicae GN-1 (race 9), plant growth stage and incubation period was studied. In a commercial horticulture nursery media soil (CNS), disease severity of the seedling according to inoculum concentration increased in a dose-dependent manner, but did not in mixture of CNS and upland soil (1:1, v/v). To facilitate and acquire precise result of resistance screening of Chinese cabbage to clubroot, 10-day-old seedlings should be inoculated by drenching the spore suspension of P. brassicae to give inoculum density of $4.0{\times}10^8$ spores/pot. To develop the disease, the inoculated seedlings were incubated in a growth chamber at $20^{\circ}C$ for 3 days, and then cultivated in a greenhouse ($25{\pm}5^{\circ}C$) for five weeks. Under the optimum conditions, 25 clubroot-resistant (CR) and 3 clubroot-susceptible (CS) cultivars were tested for resistance to P. brassicae. All CR cultivars showed very clear resistance response, on the other hand all CS cultivars severly infected with the pathogen. The results suggest that this method is efficient screening method of Chinese cabbage for resistance to clubroot disease.

• Research in Plant Disease
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• v.14 no.2
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• pp.90-94
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• 2008

To investigate the severity of crown gall disease on grapevine, the ratio of healthy vs. galled grapevines and the presence of the pathogen of the disease in soil were measured in Korean vineyards. In field and greenhouse cultivations, the crown gall incidence of the cv. Kyoho grapevines was $0.4{\sim}97.9%$ and $1.4{\sim}3.8%$ and those of cv. Campbell Early was $1.2{\sim}2.1%$ and $0{\sim}1.8%$, respectively. The higher populations of Agrobacterium spp. were isolated from soils of grapeveins with crown gall than from soils of noninfected vineyards. Based on the colony shapes and growth on plates, 480 isolates of Agrobacterium spp. from 21 soil samples were collected. Only 13 isolates out of 480 developed the gall on inoculated grapevines.

• Research in Plant Disease
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• v.17 no.2
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• pp.161-168
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• 2011

To establish simple and reliable screening method for resistant radish to Plasmodiophora brassicae Woron. using soil-drenching inoculation, the development of clubroot on radish seedlings inoculated with P. brassicae GN-1 isolate according to several conditions such as inoculum concentration, plant growth stage and incubation period after inoculation was studied. To select resistant radish against clubroot, 10-day-old seedlings were inoculated with P. brassicae by drenching the roots with the spore suspension of the pathogen to give $1{\times}10^9$ spores/pot. The inoculated seedlings were incubated in a growth chamber at $20^{\circ}C$ for 3 days then cultivated in a greenhouse ($20{\pm}5^{\circ}C$) for 6 weeks. Under the optimum conditions, 46 commercial cultivars of radish were tested for resistance to YC-1 (infecting 15 clubroot-resistant cultivars of Chinese cabbage) and GN-1 (wild type) isolates of P. brassicae. Among them, thirty-five cultivars showed resistance to both isolates and one cultivar represented susceptible response to the pathogens. On the other hand, the other cultivars showed different responses against the tested P. brassicae pathogens. The results suggest that this method is an efficient system for screening radish with resistance to clubroot.

• The Korean Journal of Pesticide Science
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• v.9 no.1
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• pp.81-87
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• 2005

Ethaboxam[(RS)-N-(a-cyano-2-thenyl)-4-ethyl-2-(ethylamino)-1,3-thiazole-5-carboximide] is a novel fungicide with high level of activity against Oomycetes fungi. The control effects of ethaboxam technical and various ethaboxam formulations were investigated against P. brassicae, the causal agent of clubroot disease in Chinese cabbage. When ethaboxam was applied to infested soil, club formation caused by P. brassicae was strongly inhibited at 8.33 mg/L soil and $EC_{50}$ of ethaboxam was 2.65 mg/L soil. Five ethaboxam formulations [10% suspension concentrate (SC), 15% SC, 2% granule (GR), 5% GR, 25% wettable powder] and mixture formulation of ethaboxam and metalaxyl (3%+1% GR) exhibited good efficacy against the pathogen. 10% SC, 15% SC, and 2% GR formulations of ethaboxam showed better disease controlling efficacy on Chinese cabbage clubroot than the other formulations. The $EC_{50}$ values of 10% SC, 15% SC, and 2% GR formulations of ethaboxam were 3.72 mg AI/L soil, 1.1 mg AI/L soil, and 4.95 mg AI/L soil, respectively. Among them, soil drenching application by 15% SC formulation of ethaboxam exhibited the most in vivo antifungal activity on P. brassicae. These results indicate that ethaboxam has a high potential for the control of clubroot disease.

• The Korean Journal of Pesticide Science
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• v.9 no.4
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• pp.422-428
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• 2005

In vivo antifungal activity of 44 fungicides consisting of 3 clubroot fungicides, 7 Oomycetes fungicides, 7 botriticides, 7 blasticides, 9 sterol biosynthesis inhibitors, and 11 broad spectrum fungicides were investigated against Plamodiophora brassicae, the causal agent of clubroot disease in Chinese cabbage. When fluazinam, flusulfamide and cyazofamid, commercial fungicide to control clubroot of Chinese cabbage in Korea, were applied to infested soil, club formations by P. brassicae were strongly inhibited at pot (35 $cm^2$) per 0.63 mg. Ethaboxam and cymoxanil, Oomycetes fungicides, completely controlled Chinese cabbage clubroot at 5 mg/pot, but cymoxanil represented sever phytotoxicity. Besides, dichlofluanid and procymidone of botriticides effectively controlled the development of Chinese cabbage clubroot at 2.5 mg/pot. Chlorothalonil, quintozene and trichlamide, broad spectrum fungicides, showed disease-control efficacy of 85%, 100% and 100% at 2.5 mg/pot, respectively. Most of sterol biosynthesis inhibitors displayed the strong antifungal activity against P. brassicae on cabbage seedlings and plant growth -retarding activity. From these results, 7 fungicides were selected and further tested in vivo antifungal activity against P. brassicae in glasshouse. Among them, ethaboxam showed the most antifungal activity against P. brassicae on cabbage seedlings, followed by fenarimol, procymidone, nuarimol and chlorothalonil.

• Research in Plant Disease
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• v.17 no.2
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• pp.155-160
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• 2011

To develop the efficient screening methods for antifungal compound active to Chinese cabbage clubroot caused by Plasmodiophora brassicae, the control efficacy of three fungicides fluazinam, ethaboxam, and cyazofamid on the disease was tested under several conditions such as soil types, cultivars of Chinese cabbage, growth stages of the host, and inoculum concentrations. The in vivo antifungal activities of the fungicides on clubroot of two Chinese cabbage cultivars were hardly different. At 7- and 14-day-old seedlings, the fungicides were more effective to control of clubroot than at 21-day-old seedlings. In a commercial horticulture media soil (CNS), disease severity of untreated controls was higher and control activity of the fungicides was less than in a mixture of CNS and upland soil (1:1, v/v). Disease development of the seedlings inoculated with P. brassicae at $1.8{\times}10^7$ spores/pot to $1.1{\times}10^9$ spores/pot was almost same, but control efficacy of the fungicides was negatively correlated with inoculum dosages. To effectively select in vivo antifungal compound on Chinese cabbage clubroot, 14-day-old seedlings need to be inoculated with P. brassicae by drenching the spore suspension to give $1{\times}10^8$ spores/pot 1 day after chemical treatment. To develop clubroot, the inoculated plants are incubated in a growth chamber at $20^{\circ}C$ for 2 days, and then cultivated in a greenhouse ($20{\pm}5^{\circ}$) for four weeks.

• Horticultural Science & Technology
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• v.34 no.3
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• pp.442-452
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• 2016

Clubroot caused by Plasmodiophra brassicae Woron. is one of the most important diseases in Brassica crops worldwide. To investigate resistance of cabbage to disease caused by P. brassicae isolates, we evaluated development of clubroot on commercial clubroot resistant (CR) and non-CR cultivars, a CR line, and $F_3$ lines from a cross between a CR line and a non-CR line using several isolates of P. brassicae. Four P. brassicae isolates (DJ, HN1, GN1, and YC) were used to measure development of clubroot on 16 non-CR cabbage cultivars that have been commercialized in Korea. Although four P. brassicae isolates induced similar disease severity on non-CR Chinese cabbage, these isolates exhibited different virulence on the cabbage cultivars. The YC isolate was the most virulent, followed by the GN1, HN1, and DJ isolates. Despite differences in virulence of the isolates on the cabbage cultivars, a CR cabbage line 'YCR478' and two CR cabbage cultivars showed high resistance to 12 P. brassicae isolates including DJ, HN1, GN1, and YC. When three isolates (YC, GN1, and DJ) were inoculated onto 107 $F_3$ lines that were derived from a cross between 'YCR478' and a susceptible cabbage line 'C1176', our results showed that 89, 33, and 6 of $F_3$ lines were susceptible to YC, GN1, and DJ isolates, respectively. In aspects of resistance, 6, 36, and 67 of $F_3$ lines exhibited resistant responses to YC, GN1, and DJ isolates, respectively. Taken together, these results suggest that resistance of cabbage to clubroot is likely affected by the virulence of P. brassicae isolates.

• Research in Plant Disease
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• v.18 no.3
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• pp.210-216
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• 2012

Clubroot of Chinese cabbage by Plasmodiophora brassicae, was found to be high virulent to the Chinese cabbage, turnips and cabbage. It this study, the endophytic bacteria Flavobacterium hercynium EPB-C313, which was isolated from tissues of Chinese cabbage, was investigated the antimicrobial activity on the inactivation of resting spores and its control effect on clubroot disease by bioassay. The bacterial cells, culture solutions, and culture filtrates of F. hercynium EPB-C313 inactivate the resting spores of P. brassicae with 90.4, 36.8, and 26.0%, respectively. The clubroot was inhibited with 100% by dipping the seedlings of Chinese cabbage in culture solutions of F. hercynium EPB-C313 before planting, however the chemmical 'fluazinam' was 91.7% in pot tests. Complex treatment were highly enhanced control efficacy with 63.7% at field of 50% diseased plants by soil incorporation with the pellet contains organic matter and F. hercynium EPB-C313, seedling drench of culture solution of F. hercynium EPB-C313 and soil drench with 10 days after planting. These results imply that the F. hercynium EPB-C313 is a very useful biological control agent of clubroot disease of Chinese cabbage.

• Research in Plant Disease
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• v.14 no.3
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• pp.159-164
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• 2008

Crown gall of rose (Rosa hybrida) was observed in greenhouse during 2003-2007. The average disease incidence was up to 38.1 % and was more severe in hydroponic culture as compared to soil culture. The typical gall symptom occurred mainly on the root, crown, or both, and resulted on poor rooting, growth retardation and yield loss. The reduction rate of rooting influenced by crown gall was 57.5% as compared to healthy plants on nursery stock. The location of gall formation in the plant influenced growth vigor resulting in symptoms such as poor shooting. Healthy plants produced 19.1 flowers/$m^2$, while diseased plants produced 9.5 flowers/$m^2$ during the same cultivation period. Moreover, the number of days to flowering was longer for the diseased plants than for healthy plants - 51.2 days and 39.8 days for first harvest, and 60.6 days and 52.1 days for the second harvest, respectively. Conclusively, infection on the basal stem caused serious loss of the number of shoot formation; yield loss of cut flower was 38.7% due to crown gall infection and delay of harvesting time about 8-10 days.