• Mycobiology
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• v.34 no.2
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• pp.61-66
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• 2006

Chestnut blight disease caused by Cryphonectria parasitica is widely distributed throughout chestnut tree plantations in Korea. We surveyed 65 sites located at 9 provinces in South Korea, and isolated 248 virulent and 3 hypovirulent strains of chestnut blight fungus. Hypovirulent strains had dsRNA virus in the cytoplasm, which is one of the typical characteristics of hypovirulent strains. In addition, they showed more characteristics of hypovirulent strains, i.e., suppressed conidiation, reduced pigmentation in colony color, and reduced phenol oxidase activity as well as reduced pathogenicity. Hypovirulent strains, KCPH-22, KCPH-135 and KCPH-136, had a genomic dsRNA band with the molecular weight of 12.7 kb, which is the L-dsRNA of CHV1. They also had a 2.7 kb defective dsRNA band. Single conidia isolated from hypovirulent strains were cultured and various phenotypes and absence of dsRNA bands were obtained from single conidial cultures, which means that hypovirulence transmission is unstable in asexual reproduction and variations in viral heredity by asexual reproduction. Biocontrol trial using hypovirulent strains was also carried out in the chestnut tree plantations, and canker expansion in the treated trees was stopped and healed by callus formation at the margin of the canker. These results show the potentials in successful biocontrol of chestnut blight if the vegetatively compatible hypovirulent strains could be directly used around the canker formed by compatible virulent strains.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.69.2-70
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• 2003

For the selection and breeding of chestnut varieties resistant to the chestnut blight fungus Cryphonectria parasitica, disease resistance and susceptibility of 28 varieties widely planted and growing in Korea were evaluated by artificial inoculation of a pathogenic fungus. For this experiment, a typical virulent strain (KCPC-19) was selected. Artificial inoculation was conducted into all varieties by using two different materials and methods, i.e., bark and wood tissue sections in the laboratory and living trees in the field. In the bark and wood tissue section method, the size of necrotic area and canker development on chestnut varieties were examined and compared 4 days after inoculation. There were wide variations of chestnut varieties in disease resistance and susceptibility against chestnut blight fungus, but 3 varieties, Daebo！, Ishizuchi, and Sandae, were shown to be relatively resistant to the disease with the necrotic area of 0.95-1.03 cm2, while Arima was the most susceptible with the size of 2.0 cm2. In the living tree inoculation examined 5 weeks after inoculation, 3 varieties, Daebo, Ishizuchi, and Riheiguri, showed the higher resistance, but Tono 2 did the highest susceptibility among tested varieties.

• The Plant Pathology Journal
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• v.18 no.1
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• pp.23-29
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• 2002

A total of 672 Cryphonectria parasitica was isolated from 2,536 blight lesions on chestnut twigs, which were collected from major chestnut plantations all over Korea. Isolation rates of each province ranged from 13.5% in Jeonbuk-ds to 37.4% in Gyeongnam-do, with an average rate of 25.6%. The isolates were classified into six groups according to color and shape of colony on PDA: smooth margin (S), irregular margin (I), yellow to brown (Y), white (W), and white with yellow center (C). Among these groups, IY was the most abundant with an isolation rate of 65%. On the other hand, SW, SC, IW, and SY were quite rare, with isolation rates ranging from 1.5% to 5.8%. When the 672 isolates were inoculated on the chestnut twigs,380 isolates (56.5%) caused lesions larger than the standard virulent isolate EPISS-2, while 158 isolates (23.4%) caused smaller lesions than the standard hypovirulent isolate UEP-1. However, 87.4% of the isolates belonged to the virulent group and only 12.6% belonged to the hypovirulent group based on Bavendamm test. In the provinces of Jeonnam-do, Jeonbuk-do, and Gyeongnamdo, which have high density of chestnut trees, the rates of hypovirulent-like isolates were over 20%.

• Korean Journal Plant Pathology
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• v.12 no.1
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• pp.58-65
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• 1996

한국의 수도 재배 지대에서 문제가 되는 다년생 논잡초 올방개에 자연상태에서 기주특이적으로 기생하여 올방개 줄기를 고사시키는 병원균인 Epicoccosorus nematosporus를 우리나라에서 처음으로 분리, 동정하였으며, 이 병을 올방개 지문무늬병(Finegerprint stem blight disease of water chestnut)으로 명명하였다. 분생포자는 분생자층 위에서 형성이 되며 무격막, 단핵이며, 44.5~72 $\mu\textrm{m}$ 크기의 양끝이 뾰족한 선충 모양이다. 갈색의 병반상에서 흑색의 분생자층은 발달하여 특이한 지문무늬를 형성하는 것이 특징이다. 이 병균은 전국의 올방개가 자라는 논에서 분포하며 매년 발생한다. 온실 접종시 초기의 병징은 접종후 4~5일만에 바늘끝 모양의 회흑색의 반점으로 나타나며 시간이 경과하면서 병반은 급속도로 진전하여 접종후 10~15일 정도 후 약 10mm 내외의 갈색병반이 형성이 되어 올방개 줄기를 감싸고 그 줄기 전체는 고사하게 된다. 분생포자 현탁액(3.2$\times$10\ulcorner conidia/ml)을 온실 조건하에서 분무접종 하였을 때 20일 이내에 약 78.0~93.3% 정도의 고사율을 나타내었다. 올방개 지문무늬병균의 분생포자 현탁액(3.2$\times$10\ulcorner conidia/ml)을 온실 조건하에서 벼 등 31개 작물과 피 등 15개 잡초의 유묘에 접종하였을 때 올방개를 제외한 어떤 식물에도 병원성이 없었다.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2000.10a
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• pp.28.1-28
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• 2000

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.45.1-45
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• 1999

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2003.10a
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• pp.23-23
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• 2003

Chestnut blight, caused by Cryphonectria parasitica, is the most destructive disease of American and European chestnut trees. A total of 672 C prasitica was isolated from blight lesion on chestnut twigs, which were collected from major chestnut plantations all over Korea in 1999. Isolation rates were over 30% in Kyunggj-, Kyongnam-, and Chonnam-do. The highest isolation rate was 37.4% and recorded in Kyongnam-do. On the other hand, Chonbuk-do had the lowest isolation rate as 13.5%. In grouping of C parasitica by colony shape and color, yellow colony with irregular margin were the most dominant colony type with a frequency of 65.2%. When the 672 isolates were inoculated on the chestnut twigs, 380 isolates (56.5%) caused lesions larger than the standard virulent isolate EP155-2, while 158 isolates (23.4%) caused smaller lesions than the standard hypovirulent isolate UEP-1. In Bavendamm test that determines phenol oxidase activity, 97.1% of all the isolates resulted the same or darker discoloration than EP155-2, and only 12.2% resulted the same or lighter discoloration than UEP-1. In the vegetative compatibility (VC) tests, total 670 isolates were divided into 121 VC groups (VCGs). Kyongnam-, Chonnam-, and Chungnam-do, the three principal chestnut plantation area, had 49, 33, and 27 VCGs, respectively. Among the VCGs, the biggest VCG, KR-VC104, was composed of 164 isolates and the second biggest VCG had 62 isolates. But, 64 of 121 VCGs consisted of sole member. More than 65.8% of KR-VC104, was isolated from the three provinces, Kyongnam-, Kangwon-, and Chungbuk-do. In KR-VC104, 62.8%, 59.1%, and 85.9% of the isolates looked like virulent in colony type, pathogenicity test, and Bavendamm test. In ds-RNA detection tests using cellulose chromatography, 77 of total 650 isolates were ds-RNA positive and detected ds-RNA segments were approximately 12kb, 3kb, 2.7kb, 2kb, and 1.8kb in size. Among the 77 isolates, 46 isolates had 12kb and 25 isolates had 12kb and 2.7kb. Other 6 Isolates had small ds-RNA segments. Kyongnam-, Chonnam-, and Chungnam-do had 43, 16, and 5 ds-RNA positive isolates, respectively. Among the 121 VCGs, only 29 VCGs had ds-RNA positive isolates.(중략)

• Journal of Korean Society of Forest Science
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• v.95 no.1
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• pp.139-144
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• 2006

Chestnut trees have been severely damaged by the various cankers in Korea. Field surveys for elucidating the relationships between disease occurrence and environmental factors, i.e., tree age, temperature, rainfall precipitation, direction, degree of slope, chemical properties of soils, and so on, were carried out in the chestnut tree plantations located at Gyeongnam, Jeonnam, Chungnam, and Gyeonggi-Do Province. Totally, one thousand and one hundred thirty seven trees from 36 experiment plots were investigated. Trees infected by at least one of the canker fungi were estimated up to 66%. The most severely infested area was Sunchon in Jeonnam Province with the rate of 80%, while the most lightly infested area was Kongju in Chungnam Province with 39%. Disease occurrence was found to be highly correlated with tree age. The disease occurred most frequently on trees ranged from 7 to 12 years old, while it was relatively low on trees below 5 years old or above 25 years old. Canker positions on the tree formed by the pathogenic fungi were most often at 1.6-2.0m above the ground. Over five hundreds bark samples from the canker area on the tree were collected and the pathogenic fungi were isolated. The most commonly isolated fungus was identified as Cryphonectria parasitica, the chestnut blight fungus.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2002.11a
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• pp.53.1-53
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• 2002

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.10a
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• pp.14.2-14
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• 1999