• Research in Plant Disease
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• v.6 no.1
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• pp.23-26
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• 2000

Effects of infection time of the clubroot pathogen, Plasmodiophora brassicae, on yield loss of Spring-sown Chinese cabbage plants were examined in field experiments. Yield loss of Chinese cabbage plants increased as the infection time becomes early. Plants infected at 20 days after transplanting or earlier were completely killed before harvest, and those infected at 30 days after transplanting were healthy in appearance but their head weights were reduced to 59% with poor commodity value. The plants infected 40 days after transplanting were not affected in yield. Development of root hairs in diseased plants was greatly reduced as the infection progressed, and root length was reduced to 1/2 to 1/3 of that of healthy plants. root galls were first developed 20 days after inoculation and rapidly enlarged to reach the peak in size 20 days from initial development, and decayed thereafter. Development and decay of root galls tended to be faster at later season as air temperature became high, regardless of the infection time. Diseased plants started to wilt approximately 10 days after root gall development. Root galls began to decay 10 days after initial plant wilting, and then were completely rotten within following 10 days. Based on the results, root gall development stages on spring-sown Chinese cabbage plants could be grouped into 20 days of root gall enlargement period, and 10 days of root gall decay period, followed by survival period in soil.

• Research in Plant Disease
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• v.19 no.3
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• pp.201-207
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• 2013

This research was performed to establish basic technology for Chinese cabbage clubroot chemical control by investigating the soil contamination of Plasmodiophora brassicae in major producing regions of fall Chinese cabbage. PCR primers were developed to detect P. brassicae, a causal agent of Chinese cabbage club-root that generally occurs in Cruciferae family. A primer set, PbbtgF761 and PbbtgR961, specifically amplified a 245 bp fragment from P. brassicae only. At places well known for fall Chinese cabbage, 10 out of 33 in Haenam-gun, 5 out of 13 in Yeongam-gun and Yeonggwang-gun, 1 out of 6 in Gochang-gun, 2 out of 12 in Hongseong-gun, and 5 out of 17 in Dangjin-si resulted positive for P. brassicae contamination. The results show that the soil contamination rate of P. brassicae was 30.3% in Haenam-gun, 38.5% in Yeongam-gun and Yeonggwang-gun, 16.7% in Gochang-gun, 16.7% in Hongseong-gun, and 29.4% in Dangjin-si. The six places where Chinese cabbage clubroot was visible by naked eye were 100% confirmed by the PCR test of the P. brassicae contaminated soil. Thus, simple PCR test may be utilized as an index to decide on chemical control of P. brassicae.

• Research in Plant Disease
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• v.13 no.1
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• pp.45-49
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• 2007

Single spores were isolated from infected roots of Chinese cabbage with a typical clubroot symptom, collected from different Chinese cabbage cultivation areas in Korea. When the single spore isolates were inoculated on Chinese cabbage, radish, turnip, kale, leaf mustard and Williams' differential varieties, among 321 roots harvested two weeks after inoculation, a visual symptom was observed on only one root and light/uncommon symptoms were done on 70 roots. These 71 individuals were homogenized and used as inocula. These inocula caused generally higher pathogenicity than that of single spore. Finally 15 isolates, with enough growth for conducting further experiment, were selected. These 15 individuals were grouped four, seven, two and two into race 1, race 4, race 9 and race 11, respectively, using Williams' differential set. It was confirmed that race 4 were dominantly present in Korea. These 15 had been obtained from roots of Chinese cabbages, radishes and turnips inoculated with single resting spores and had shown pathogenicity to Laurentian and Wilhelmsburger belong to Rutabaga in Williams' differential variety set. Therefore, we assume that such characteristic pathotypes including race 4, especially, of P. brassicae showing strong pathogenicity to Chinese cabbage, radish and turnip may be dominant in Korea.

• The Plant Pathology Journal
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• v.17 no.6
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• pp.369.5-370
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• 2001

• The Plant Pathology Journal
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• v.17 no.6
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• pp.369.4-369
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• 2001

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2003.04a
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• pp.123-123
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• 2003

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2005.04a
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• pp.77-77
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• 2005

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.384-384
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• 2005

• Proceedings of the Korean Society of Plant Biotechnology Conference
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• 2005.11a
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• pp.344-344
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• 2005

• Journal of Microbiology and Biotechnology
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• v.18 no.11
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• pp.1741-1746
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• 2008

This study was conducted to select endophytic actinomycetes as biocontrol agents against Chinese cabbage clubroot caused by Plasmodiophora brassicae. A total of 81 endophytic actinomycetes were isolated from surface-sterilized roots of Chinese cabbage that was grown on paddy field and upland soils collected from various locations in Korea. By using 16S ribosomal DNA (rDNA) gene sequencing, they were classified to 8 actinobacterial genera. The genus Microbispora (67%) was most frequently isolated, followed by Streptomyces (12%) and Micromonospora (11%). Three of the 81 isolates, when inoculated in germinated Chinese cabbage seeds and then transplanted to pots, effectively suppressed the occurrence of a post-inoculated strain of P. brassicae in the pots. They showed control values of 58% for strain A004, 33% for strain A011, and 42% for strain A018. Based on cell wall components, morphological characteristics, and phylogenetic analyses, the three antagonistic isolates were identified as Microbispora rosea subsp. rosea (A004 and A011) and Streptomyces olivochromogenes (A018). Further researches on the field efficacy and action modes of the three actinomycetes are in progress.