• The Korean Journal of Pesticide Science
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• v.12 no.1
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• pp.88-96
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• 2008

To obtain protoplasts of Colletotrichum acutatum JC24, conidia were inoculated onto cellophane membrane placed on PDA and incubated at $25^{\circ}C$ for 20 hrs under the dark condition. Cellophane membranes, where mycelia were incubated, were soaked into 2% lysing enzyme solution prepared with 0.02 M phosphate buffer (pH 7.0) including 1.2 M sorbitiol. After treatment in 2% enzyme solution for 2 - 3 hrs, it could be possible to harvest $2-3\;{\times}\;10^6$ protoplasts/mL. The effect of several fungicides on reversion ratio was determined by using the protoplasts obtained from C. acutatum JC24. Any protoplasts could not be reversed to mycelia on reversion PDA amended with $10\;{\mu}\;g\;mL^{-1}$ of propineb. With tebuconazole, inhibition ratio of protoplast reversion was 100 and 0.9% at 0.5 and $0.1\;{\mu}\;g\;mL^{-1}$, respectively, while inhibitory effect on mycelial growth was 85.1 and 75.7%. The inhibitory tendency of carbendazim on protoplast reversion was as same as mycelial growth. In the case of strobilurins, trifloxystrobin and kresoxim-methyl, they only could inhibit protoplast reversion of C. acutatum JC24, when salicylhydroxamic acid (SHAM) was amended into reversion PDA with strobilurins.

• The Korean Journal of Pesticide Science
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• v.18 no.3
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• pp.161-167
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• 2014

This study was conducted to investigate the resistance of Botrytis cinerea to azoxystrobin, which belongs to strobilurin fungicides. The sensitivity of B. cinerea isolates, which were collected from infected pepper, strawberry, cucumber and tomato by a single spore isolation, to the fungicide was tested through a agar dilution method on PDA amended with fungicides and $100{\mu}g\;mL^{-1}$ of salicylhydroxamic acid (SHAM). All isolates of B. cinerea tested in this study were classified as a sensitive and a resistant group by $1.0{\mu}g\;mL^{-1}$ of $EC_{50}$ value to azoxystrobin. While the sensitive isolates accounted for 46.5% of B. cinerea population, the resistant ones did for 53.5%. According to the regions isolating B. cinerea, the highest isolation frequency was showed as 81.1% in Chungnam among the all. Among 4 host plants as pepper, strawberry, cucumber and tomato, the highest isolation frequency was obtained in strawberry, while the lowest was done in pepper. The isolate resistant to azoxystrobin showed the cross resistance to other fungicides included into strobilurins as kresoxim-methyl and trifloxystrobin. In spite of an excellent efficacy of strobilurins, it should be taken care to use them in the field, because of the high risk in the fields.

• Bulletin of the Korean Chemical Society
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• v.33 no.8
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• pp.2627-2634
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• 2012

Strobilurins are one of the most important classes of agricultural fungicides. To discover new strobilurin derivatives with high activity against resistant pathogens, a series of novel ${\beta}$-methoxyacrylate analogues were designed and synthesized by integrating substituted pyrimidine with a strobilurin pharmacophore. The compounds were confirmed and characterized by infrared, $^1H$ nuclear magnetic resonance, elemental analysis and mass spectroscopy. The bioassays indicated that most of the compounds (1a-1h) exhibited potent antifungal activities against Colletotrichum orbiculare, Botrytis cinerea Pers and Phytophthora capsici Leonian at the concentration of 50 ${\mu}g/mL$. Exhilaratingly, compound 1d (R=3-trifluoromethylphenyl) showed better antifungal activity against all the tested fungi than the commercial strobilurin fungicide azoxystrobin.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.616-628
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• 2022

Resistance to pyraclostrobin due to a single nucleotide polymorphism at 143rd amino acid position on the cytochrome b gene has been a major source of concern in red pepper field infected by anthracnose in Korea. Therefore, this study investigated the response of 24 isolates of C. acutatum and C. gloeosporioides isolated from anthracnose infected red pepper fruits using agar dilution method and other molecular techniques such as cytochrome b gene sequencing, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and allele-specific polymerase chain reaction (PCR). The result showed that four isolates were resistant to pyraclostrobin on agar dilution method and possessed GCT (alanine) codon at 143rd amino acid position, whereas the sensitive isolates possessed GGT (glycine). Furthermore, this study illustrated the difference in the cytochrome b gene structure of C. acutatum and C. gloeosporioides. The use of cDNA in this study suggested that the primer Cacytb-P2 can amplify the cytochrome b gene of both C. acutatum and C. gloeosporioides despite the presence of various introns in the cytochrome b gene structure of C. gloeosporioides. The use of allele-specific PCR and PCR-RFLP provided clear difference between the resistant and sensitive isolates. The application of molecular technique in the evaluation of the resistance status of anthracnose pathogen in red pepper provided rapid, reliable, and accurate results that can be helpful in the early adoption of fungicide-resistant management strategies for the strobilurins in the field.

• The Korean Journal of Pesticide Science
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• v.12 no.2
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• pp.168-176
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• 2008

Recently damage of rice bakanae disease disseminated by infected seeds increased in paddy field in Korea. For controlling rice bakanae disease, the efficacy of 17 fungicides was assessed by 5 kinds of bioassay, spore germination test (SGT), mycelial growth test, detection test on Komada's medium (KDT), pouch test (PT) and greenhouse test (GT). Among ergosterol biosynthesis inhibiting fungicides, prochloraz showed a high controlling activity in all the assay systems while the others showed very low activity except for $500\;{\mu}g/ml$ of hexaconazole in GT and $500\;{\mu}g/ml$ of triflumizole in KDT. Although benomyl and the mixture of benomyl and thiram showed a good activity at 100 and $500\;{\mu}g/ml$ in SGT and PT, respectively, in GT they did a middle activity. Trifloxystrobin and kresoxim-methyl included in strobilurins showed a good activity even at $20\;{\mu}g/ml$ in KDT as well as a middle activity in SGT. Also a high activity not only at $10\;{\mu}g/ml$ in SGT but also at $100\;{\mu}g/ml$ KDT was detected in thiram. The activity of fludioxonil was confirmed in SGT, KDT and PT. Based on these results, it is very important to determine a bioassay system, because the fungicidal activity against rice bakanae disease was fluctuated depending on a assay systems as well as the mechanism of fungicide.

• Research in Plant Disease
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• v.28 no.3
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• pp.122-131
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• 2022

Colletotrichum acutatum s. lat. 20JDS8 sensitive and 20CDJ6 resistant to pylaclostrobin were used to investigate the cross-resistance with fungicides belonging to the strobilurins and the characteristics of fungicidal controlling activities with different mechanisms against the isolate resistant to the fungicide. The resistant isolate of 20CDJ6 also showed the resistance to azoxystrobin, trifloxystrobin, and kresoxim-methyl, suggesting that there is a cross-resistance relationship. All fungicides with different action mechanisms inhibited mycelial growth of both susceptible and resistant isolates of C. acutatum s. lat., but their disease control effects in fruits were different according to the fungicides. The disease control effect of isopyrazam against 20JDS8 and 20CDJ6 was very low, and fluazinam showed a control effect of 91.9% and 88.1% against 20JDS8 and 20CDJ6 only when it was treated before inoculation by spraying spore suspensions on pepper fruits without wounds. Tebuconazole and prochloraz effectively inhibited not only the mycelial growth of 20JDS8 and 20CDJ6 on potato dextrose agar medium, but also disease incidence in red pepper fruits. As a result of this study, C. acutatum s. lat. 20CDJ6 resistant to pyraclostrobin showed cross-resistance with other strobilurin fungicides. In addition, we think that fluazinam, tebuconazole, and prochloraz can be recommended as alternative fungicides for the control of red-pepper pyranthracnose pathogens resistant pyraclostrobin. However, fluazinam can be effective only if it is treated protectively before the occurrence of the disease.