• The Plant Pathology Journal
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• 제16권4호
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• pp.222-226
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• 2000

In disease surveys from 1986 ti 1998, disease incidence of tobacco black shank was gradually increased in burley tobacco from 1996. To study the causes of the disease occurrence, one hundred and fourteen isolates of Phytophthora parasitica var. nicotianae (Ppn) were collected from burley tobacco-growing areas in the southern part of Korea during 1996-1997, and tested in vitro for meatlaxyl sensitivity which was determined by measuring the mycelial growth on corn meal agar (CMA) amended with metalaxyl. Of the tested isolates, 78.1% showed sensitive to metalaxyl, having $\textrm{ED}_{50}$ values less than 1.0 $\mu\textrm{g}/$\textrm{ml}, while 1.7% was resistant weth $\textrm{ED}_{50}$ greater than 100 $\mu\textrm{g}/$\textrm{ml}. Ppn isolates from three provinces, Chungnam, Chonbuk and Chonnam showed similar distributions of metalaxyl sensitivity. Metalaxyl-resistant isolates were not significantly different from metalaxyl-sensitive ones in mycelial growth rate, chlamydospore formation capacity and size of the spore, and pathogenicity on tobacco plant (cv. Burley 21). These results suggest that the metalaxyl-resistant Ppn in burley tobacco may be one of the major factors to cause the higher occurrence of the tobacco black shank in the burley tobacco-growing area.

• 한국토양비료학회지
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• 제51권1호
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• pp.28-34
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• 2018

Yuzu (Citrus junos) gummosis disease, caused by Phytophthora nicotianae, was first reported in 1997. As known in citrus, Phytophthora is the most fastidious soil-borne pathogen to control. In order to minimize its damage to Citrus spp., integrated pest management (IPM) approach, including fungicide chemicals and resistant cultivars, is necessary. Therefore, in this study we tried to evaluate tolerance of yuzu cultivars and its related species against yuzu Phytophthora. Trifoliate orange was evaluated as a susceptible host to yuzu Phytophthora by both mycelial growth onto extract media and immature fruit inoculation. However, in zoospores spray-inoculation on 2-year-old cuttings tree, trifoliate orange appeared to have a resistant property as showing less than 6% diseased leaf rate. Among yuzu cultivars only 'Namhae No. 1' appeared resistant property against both P. nicotianae and P. citrophthora. The 'Namhae No. 1' showed 5.7% and 10.6% diseased leaf ratio by P. nicotianae and P. citrophthora, respectively. Clearly, in order to reduce damages caused by two yuzu Phytophthora, we suggest that growers may utilize a trifoliate orange as a rootstock and 'Namhae No. 1' as a scion for fruit production.

• Mycobiology
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• 제31권4호
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• pp.229-234
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• 2003

A total of 24 isolates of Phytophthora infestans were tested and analyzed for their resistance to metalaxyl fungicides. Sensitivity to metalaxyl was determined by growing isolates on 20% V8 medium amended with 0, 5, and 100 ${\mu}g/ml$ metalaxyl. Four isolates among the 24 tested were resistant to metalaxyl. Eleven isolates were intermediate and nine isolates were sensitive. Amplified fragment length polymorphism(AFLP) assay was used to identify the amplification products of resistant isolates. As a result, selected fragments were cloned, sequences and primer pairs were developed which linked to metalaxyl insensitivity in P. infestans using competitive PCR.

• The Plant Pathology Journal
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• 제36권6호
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• pp.579-590
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• 2020

Botrytis cinerea, which causes gray mold disease in more than 200 plant species, is an economically important pathogen that is mainly controlled by synthetic fungicides. Synergistic fungicide mixtures can help reduce fungicide residues in the environment and mitigate the development of fungicide-resistant strains. In this study, we screened microbial culture extracts on Botrytis cinerea to identify an antifungal synergist for tebuconazole. Among the 4,006 microbial extracts screened in this study, the culture extract from Schizophyllum commune displayed the most enhanced activity with a sub-lethal dosage of tebuconazole, and the active ingredient was identified as schizostatin. In combination with 5 ㎍/ml tebuconazole, schizostatin (1 ㎍/ml) showed disease control efficacy against gray mold on tomato leaf similar to that achieved with 20 ㎍/ml tebuconazole treatment alone. Interestingly, schizostatin showed demethylation inhibitor (DMI)-specific synergistic interactions in the crossed-paper strip assay using commercial fungicides. In a checkerboard assay with schizostatin and DMIs, the fractional inhibitory concentration values were 0.0938-0.375. To assess the molecular mechanisms underlying this synergism, the transcription levels of the ergosterol biosynthetic genes were observed in response to DMIs, schizostatin, and their mixtures. Treatment with DMIs increased the erg11 (the target gene of DMI fungicides) expression level 15.4-56.6-fold. However, treatment with a mixture of schizostatin and DMIs evidently reverted erg11 transcription levels to the pre-DMI treatment levels. These results show the potential of schizostatin as a natural antifungal synergist that can reduce the dose of DMIs applied in the field without compromising the disease control efficacy of the fungicides.

• 농약과학회지
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• 제19권3호
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• pp.312-316
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• 2015

본 연구에서 단감 탄저병 방제력을 수립하기 위하여 단제 6종류와 복합제 6종류 총 12종류의 약제를 시중에서 구입하여 시험에 공시하였다. EC50 값 결과에 의해서 Quinone계의 Dithianon, Triazole계의 Metconazole, Dithiocarbamate계의 Propineb을 사용하였다. 최종적으로 사용한 세 가지 약제의 약제 처리 횟수에 따른 단감 탄저병 방제효과는 신초와 과실에서 Quinone계 약제인 Dithianon 약제가 가장효과가 좋은 것으로 나타났으며 Triazole계 약제인 Metconazole와 Dithiocarbamate계 약제인 Propineb약제는 효과가 유사하게 나타났다. 또한 2회 처리구에서는 과일과 신초에 탄저병이 발생하였고 8회 처리구와 4회 처리구에 비하여 효과가 낮은 것으로 나타났다. 8회 처리구와 4회 처리구에서는 두 처리 구 모두 탄저병 발생이 유사하게 나타났으며 앞에서 언급한 바와 같이 하였듯이 경제적 비용, 노동력 및 농약의 오남용을 줄이기 위해서는 4회 처리하는 것이 효율적이라고 본 연구 결과로 도출되었다.

• The Plant Pathology Journal
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• 제39권4호
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• pp.351-360
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• 2023

Citrus melanose, caused by Diaporthe citri, has been one of the serious diseases, and chemical fungicides were used for protection in many citrus orchards of Jeju Island. Establishing a disinfectant resistance management system and reducing pesticide usage would be important for contributing to safe agricultural production. In this study, monitoring of chemical resistance was performed with 40 representative D. citri isolates from many citrus orchards in Jeju Island. Four different fungicides, kresoxim-methyl, benomyl, fluazinam, and prochloraz manganese, with seven different concentrations were tested in vitro by growing the mycelium of the fungal isolates on the artificial medium potato dextrose agar. Among the 40 fungal isolates, 12 isolates were investigated as resistant to kresoxim-methyl which could not inhibit the mycelium growth to more than 50%. Especially isolate NEL21-2 was also resistant against benomyl, whose hyphae grew well even on the highest chemical concentration. However, any chemical resistance of fungal isolates was found against neither fluazinam nor prochloraz manganese. On the other hand, in vivo bio-testing of some resistant isolates was performed against both kresoxim-methyl and benomyl on young citrus leaves. Typical melanose symptoms developed on the citrus leaves pre-treated with both agrochemicals after inoculation with the resistant isolates. However, no or less symptoms were observed when the susceptible isolates were inoculated. Based on these results, it was suggested that some resistant isolates of D. citri occurred against both systemic fungicides, which may be valuable to build a strategy for protecting citrus disease.

• 식물병연구
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• 제12권1호
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• pp.32-39
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• 2006

다양한 작물로부터 분리한 4종의 탄저병균, C. gloeosporioided, C. acutatum, C. coccodes 및 C. dematium 등의 균주들에 대하여 여러 가지 살균제, 즉 carbendazim, carbendazim과 diethofencarb와의 혼합제, 4개의 보호용 살균제 및 3개의 ergosterol 생합성 저해(EBI) 살균제 등에 대한 약제 반응을 조사하였다. Benzimidazole계에 속하는 carbendazim에 대해서 4종의 Colletotrichum의 반응은, C. acutatum은 사용한 6개의 균주 모두 $EC_{50}$값은 $0.001{\sim}3.04{\mu}g/ml$ 사이에 있었으며, 모든 균주의 MIC 값은 $100{\mu}g/ml$ 이상이었다 고추와 사과, 딸기에서 분리한 C. gloeosporioides는 carbendazim에 대해서 저항성과 감수성 반응이 뚜렷하게 구별되었는데, 고추의 두 균주는 $EC_{50}$값은 0.24와 $0.01{\mu}g/ml$이었으며 MIC 값 역시 $1.0{\mu}g/ml$ 이었다. 이러한 반응은 사과와 딸기에서 분리한 균주 중에서 감수성 반응을 보이는 균주인 B13과 138, 그리고 CGF89와 94, 252에서도 비슷한 경향을 보였다. 그러나 저항성 균주로 판명된 B90, 92, 147과 CGF50, 54, 222는 $EC_{50}$값과 MIC 값 모두가 $100{\mu}g/ml$를 상회하였다. C. gloeosporioides는 carbendazim과 역상관 교차 저항성을 보이는 diethofencarb와 carbendazim의 혼합제에 대해서는 모두 $1{\sim}100{\mu}g/ml$의 MIC값을 보였지만, C. acutatum은 $100{\mu}g/ml$이상의 MIC값을 보였다. Carbandazim에 대하여 C. coccodes는 C. acutatum과 그리고 C. dematium는 C. gloeosporioides의 감수성 균주들의 반응과 유사한 반응을 보였다. 4종의 보호용 살균제에 대해서는 C. acutatum은 C. gloeosporioides보다도 높은 저항성인 반응을 보였다. 그러나 ergosterol 생합성 저해 살균제에 대해서는 4종의 탄저병균이 일정한 경향을 보였다.

• International Journal of Industrial Entomology and Biomaterials
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• 제10권2호
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• pp.119-123
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• 2005

Benomyl-resistant mutants of entomopathogenic fungus, Metarhizium anisopliae were isolated and their physiological characteristics were investigated. These militants were obtained spontaneously or by UV irradiation in benomyl-treated media. Four spontaneous (S-2, S-11, S-18, S-19) and four UV-induced (UV-4, UV-5, UV-19, UV-24) mutants, which grow stably and normally were selected. No significant differences in conidia or hyphal shape, conidia viability, mycelial biomass, or virulent to the diamondback moth were observed between the wild type and their mutants. But differently from the mycelial growth of other benomyl-resistant mutants which was slower than that of the wild type on a modified Czapek-Dox, SDAY, $4\%$ chitin, or $1\%$ skim milk medium, that in the spontaneous mutants, S-18 and S-19, did not show any difference from the wild type. Especially, S-18 and S-19 grew well at benomyl concentrations up to 50 times or higher than that which inhibits wild type proliferation. These results suggested that S-18 and S-19 could potentially be used with the fungicide, benomyl.

• The Plant Pathology Journal
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• 제17권3호
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• pp.149-153
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• 2001

A total of 2109 isolates of Botrytis cinerea were collected from infected plants fo strawberry, tomato, and cucumber in Korea from 1994 to 1996. Based on in virtotests for mycelial growth on potato-dextrose agar containing fungicides, the esolates were classified into six phenotypic groups : SSR, SRR, RSS, RRS, RSR, and RRR, representing sensitivity (S) or resistance (R) to carbendazim, procymidone, and diethofencarb. In that order the isolation frequencies of the SSR, SRR, RSS, RRS, RSR, and RRR phenotypes were 28.7, 1.1, 28.8, 39.4, 1.0, and 0.9%, respectively. Three isolates from each SSR, SRR, RSS, RRS, and RSR and an isolate of RRR phenotype were selected and evaluated for their fitness-related characteristics such as pathogenic aggressiveness, mycelial growth rate, sporulation, and sclerotial formation. Competitive abilities of the SSR, SRR, RSS, RRS, and RSR phenotypes were also compared by inculating mixtures of conidial suspensions of two phenotypes to cucumber plant, and then determining re-isolation frequencies from lesions. In general, significant differences in fitness-related characteristics, except pathogenic aggressiveness, were found not only between but also within phenotype groups. In the competitiveness tests, carbendazim-sinsitive phenotypes (SSR and SRR) were found to be more competitive than the resistant ones (RSS and RSR), whereas, the procymidone-resistant phenotypes (SRR and RRS) appeared to be more competitive than the sensitive ones (SSR, RSS, and RSR). There was no consistent dominance in competitiveness between the diethofencarb-resistant and sensitive phenotypes. The RSR phenotype was the least competitive among the five phenotypes.

• 한국식물병리학회:학술대회논문집
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• 한국식물병리학회 2003년도 정기총회 및 추계학술발표회
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• pp.117.1-117
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• 2003

Phytophthora blight, caused by P. capsici, is very important disease of pepper. Many fungicides to control of Phytophthora blight have been developed, but most of fungicides disappeared in short periods. Nowadays dimethomorph was known as one of the most effective to control of this disease. P. capsici isolates from pepper fields were collected and surveyed their growth in dimethomorph amended V8 medium in order to evaluate their fungicides resistance. The fungicide resistant isolates were not founded among them. Most of the sensitive isolates were inhibited perfectly in V8 medium amended with 10ppm dimethomorph. Mutants of P. capsici by dimethomorph, was grown very well in 250ppm. The difference of pathogenicity, colony morphology, drug response, RT-PCR results was identified between sensitive and resistance isolates. This study should be provided a basic information about the occurrence of dimethomorph resistant isolates and genetic changes in P. capsici population.