• Research in Plant Disease
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• v.25 no.4
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• pp.188-195
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• 2019

Among 6 fungicides, fluazinam, which had an excellent inhibitory effect on mycelial growth and spore germination, was also effective in controlling jujube anthracnose in the field. While EC₅₀ values of metconazole and tebuconazole ranged from 0.2 to 0.9 ㎍/ml and from 0.4 to 1.1 ㎍/ml against the mycelial growth, respectively, each inhibitory effect on spore germination was low by 7.4% and 11.1% at 50.0 ㎍/ml. In the field test, they showed the control value of 80.5% and 77.0%, respectively. The protective fungicides, as mancozeb and folpet, which had a low inhibitory effect on the mycelial growth, but had a high inhibitory effect of spore germination, showed excellent disease control activities by 87.6% and 92.0% in the field. Showing a result of resistance monitoring conducted with the isolates of Colletotricum gloeosporioides, the resistance against carbendazim was already generated in the field, but it was thought that there was no resistance to pyraclostrobin, fluazinam and tebuconazole. However, if the resistance factor value of the population of C. gloeosporioides isolates to pyraclostrobin was high by 160.4, the diversity of the response to the fungicide in the population was high, so it should be taken more attention to the resistance management.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.30-36
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• 2012

BACKGROUND: The resistance of rice bakanae disease pathogens against the fungicide prochloraz has been reported. Understanding the resistance mechanisms is an important for better control of the pathogens. In the present study, we investigated the resistance mechanisms of Fusarium fujikuroi CF337 (CF337) against prochloraz. METHODS AND RESULTS: Morphological changes in the cell wall of CF337 grown in potato dextrose broth (PDB) with or without prochloraz was investigated by transmission electron microscopy. Growth inhibition of CF337 was examined in PDB containing prochloraz or an ABC transporter inhibitor or both of them. Cell wall thickness of CF337 grown in PDB with prochloraz was significantly increased from $80.73{\pm}1.99nm$ to $193.11{\pm}7.07nm$. Significant inhibition in the growth of CF337 was observed in the presence of both prochloraz and the inhibitor, but no growth inhibition was observed in the presence of the inhibitor or prochloraz. Sequence analysis of ATP-binding cassette transporter (ABC) gene of CF337 showed 70 to 80% similarities to the genes of the pathogens resistant to other fungicides. CONCLUSION: Efflux transporter system and changes in cell wall thickness were suggested as resistance mechanisms of CF337 against prochloraz.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1999.04a
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• pp.33.1-33
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• 1999

• The Korean Journal of Mycology
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• v.38 no.1
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• pp.75-79
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• 2010

A total of 25 isolates of Fusarium fujikuroi were obtained from diseased rice plants in Korea from 2006 to 2007 to assess their resistance against fungicides prochloraz and benomyl + thiram. Minimal inhibitory concentration (MIC) values of F. fujikuroi isolates were examined by agar dilution method. Most of the isolates were sensitive to the fungicides. Out of 25 isolates, six were resistant to prochloraz and three to benomyl + thiram. In addition, the isolates CF245, CF249 and CF337 showed resistant to both fungicides. The progenies ($F_1$ isolates) obtained through two different crosses between sensitive parental isolates(CF202, CF232 and CF179) and resistant parental isolate (CF337) were evaluated for their mycelial growth at different temperatures and resistance against fungicides. Mycelial growth rate of $F_1$ isolates originated from CF202 $\times$ CF232 was similar to the parental isolates. However mycelial growth rate of $F_1$ isolates originated from CF179 $\times$ CF337 was faster than their parent isolates. In case of prochloraz, distribution ratio of sensitivity(S) to resistance(R) against to the fungicide of $F_1$ isolates originated from CF202 $\times$ CF232 and CF179 $\times$ CF337 was 86 : 14 and 78 : 22, respectively. In case of benomyl+thiram, all the $F_1$ isolates originated from CF202 $\times$ CF232 were sensitive to the fungicide, however ratio of sensitivity(S) to resistance(R) against to the fungicide of $F_1$ isolates originated from CF179 $\times$ CF337 was 35 : 65.

• The Plant Pathology Journal
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• v.32 no.1
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• pp.8-15
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• 2016

To identify a novel biopesticide controlling rice blast disease caused by Magnaporthe oryzae, 700 plant extracts were evaluated for their inhibitory effects on mycelial growth of M. oryzae. The L. foenum-graecum Herba extract showed the lowest inhibition concentration ($IC_{50}$) of $39.28{\mu}g/ml$, which is lower than the $IC_{50}$ of blasticidin S ($63.06{\mu}g/ml$), a conventional fungicide for rice blast disease. When treatments were combined, the $IC_{50}$ of blasticidin S was dramatically reduced to $10.67{\mu}g/ml$. Since ABC transporter genes are involved in fungicide resistance of many organisms, we performed RT-PCR to investigate the transcriptional changes of 40 ABC transporter family genes of M. oryzae treated with the plant extract, blasticidin S, and tetrandrine, a recognized ABC transporter inhibitor. Four ABC transporter genes were prominently activated by blasticidin S treatment, but were suppressed by combinational treatment of blasticidin S with the plant extract, or with tetrandrine that didn't show cellular toxicity by itself in this study. Mycelial death was detected via confocal microscopy at 24 h after plant extract treatment. Finally, subsequent rice field study revealed that the plant extract had high control efficacy of 63.3% and should be considered a biopesticide for rice blast disease. These results showed that extract of L. foenum graecum Herba suppresses M. oryzae ABC transporter genes inducing mycelial death and therefore may be a potent novel biopesticide.

• Research in Plant Disease
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• v.26 no.2
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• pp.61-71
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• 2020

With 32 fungicides, it was examined the inhibitory effects on the mycelial growth of Alternaria dauci KACC42997 causing Alternaria leaf blight of carrot. Showing the results of the agar dilution method, the fungicides belonging to C2, C5, G1, E2, and E3 group were excellent in inhibiting mycelial growth. Protective fungicides belonging to M group, except for iminoctadine tris-albesilate, and pyraclostrobin belonging to C3 group were effective in inhibiting spore germination of pathogens. The fungicides included into C2 group inhibiting succinate dehydrogenase activity and the G1 group inhibiting demethylase activity showed the excellent inhibitory effect on mycelial growth but the inhibitory effect of spore germination was very low. However, fluazinam belonging to C5 group was excellent in inhibiting spore germination as well as mycelial growth. Especially, when 100 ㎍/ml of fluxapyroxad belonging to the C2 group was treated, 47.1% of spore formation was inhibited on the medium. In comparison of the resistance factors of 3 fungicide groups, as G, C, and E group, in populations of A. dauci isolates collected from Gumi, Pyeongchang, and Jeju, resistance factor in the population of Jeju was the lowest. However, two isolates resistant to fludioxonil belonging to E2 group were found in the isolate group of Pyeongchang, and both showed cross-resistance to iprodione and procymidone.

• The Plant Pathology Journal
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• v.32 no.6
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• pp.570-574
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• 2016

Botrytis cinerea is a necrotrophic pathogen causing a major problem in the export and post-harvest of strawberries. Inappropriate use of fungicides leads to resistance among fungal pathogens. Therefore, it is necessary to evaluate the sensitivity of B. cinerea to various classes of fungicide and to determine the effectiveness of different concentrations of commonly used fungicides. We thus evaluated the effectiveness of six classes of fungicide in inhibiting the growth and development of this pathogen, namely, fludioxonil, iprodione, pyrimethanil, tebuconazole, fenpyrazamine, and boscalid. Fludioxonil was the most effective ($EC_{50}$ < $0.1{\mu}g/ml$), and pyrimethanil was the least effective ($EC_{50}=50{\mu}g/ml$), at inhibiting the mycelial growth of B. cinerea. Fenpyrazamine and pyrimethanil showed relatively low effectiveness in inhibiting the germination and conidial production of B. cinerea. Our results are useful for the management of B. cinerea and as a basis for monitoring the sensitivity of B. cinerea strains to fungicides.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 2004.10a
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• pp.36-38
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• 2004

Ethaboxam is a new fungicidal active ingredient that inhibits growth of plant pathogens specifically belonging to Oomycetes with protective, curative, systemic and translaminar activity in plants. Modes of action studies revealed that ethaboxam simultaneously inhibits cytoskeleton formation and mitochondrial respiration of Phytophthora infestans at low concentrations. There have been no indications of resistance development when tested for baseline resistance monitoring to 261 isolates of P. infestans in Korea and Europe and 150 populations of Plasmopara viticola populations in Europe for 3 years since 2000. In a selective study with vine trees artificially inoculated with P. viticola repeatedly for 10 generations in greenhouse, there have been no changes in sensitivity to ethaboxam among four natural populations of P. viticola. Furthermore, ethamoxam has not shown any cross resistance with azoxystrobin, mefenoxam, dimethomorph and cymoxanil. Based on the study results from modes of action and resistance development, ethaboxam appears to be unlikely to develop resistance in field applications.

• Research in Plant Disease
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• v.10 no.2
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• pp.87-93
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• 2004

Rhizome rot of ginger, caused by Pythium myriotylum, a major limiting factor for its production, has occurred annually, but become severe, especially in hot and humid years with frequent rainfalls in Korea. Most studies on rhizome rot have been carried out since 1980s in the National Institute of Agricultural Sciences and Technology, Honam Crop Experimental Station and Choongnam Provincial Rural Development Administration. Many aspects of rhizome rot, such as survey of the disease incidence, taxonomy, pathogenicity and physiology of pathogen, and ecology of soilborne inocula have been studied in the researches. However, intensive studies have been concentrated on management technologies of the disease including seed-rhizome disinfection, soil sterilization, evaluation of cultivar resistance, and fungicide application, and most developed technologies have been used in commercial farmings. In future, development of resistant varieties and simple soil disinfection technologies applicable in Korean condition and economically feasible fungicide application technology have to be developed for better management.

• Proceedings of the Korean Society of Plant Pathology Conference
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• 1998.06a
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• pp.50-69
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• 1998

Dimethomorph is a novel fungicide with a high level of activity against diseases induced by certain Oomycetes, including fungal populations that are resistant to other products. In several ways, this fungicide illustrates the opportunities and challenges presented by many modern pesticides. The specific mode of action, which affects cell wall formation, is associated with a very high level of performance and low dose rates under field conditions. These low dose rates, combined with a low level of toxicity to non-target organisms present an outstanding safety profile. This same highly-specific mode of action, however, limits the spectrum of activity and suggests the need for a resistance management plan, both of which must be addressed in new product development. In addition, the biological and physiochemical properties of this, and other new products are not adequately described by the traditional classification of fungicides into“protectant”and“systemic”types. These unique profiles provide novel and useful products for disease control.