• The Korean Journal of Pesticide Science
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• v.12 no.3
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• pp.277-282
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• 2008

To assess the resistance to prochloraz, $EC_{50}$ values of Fusarium isolates obtained from rice seed were investigated through the agar dilution method. $EC_{50}$ value of 36 isolates of Fusarium spp. to prochloraz ranged from 0.020 to $1.78{\mu}g\;mL^{-1}$ with an average of $0.25{\mu}g\;mL^{-1}$. According to the species of Fusarium, the average $EC_{50}$ value was fluctuated; $0.091{\mu}g\;mL^{-1}$ for F. moniliformis, $0.11{\mu}g\;mL^{-1}$ for F. proliferatum and $0.31{\mu}g\;mL^{-1}$ for F. fujikuroi. The resistant baseline was decided at $0.5{\mu}g\;mL^{-1}$ to determine if the isolate was resistant to prochloraz or not. Based on the resistant baseline, the ratio of resistant isolates was 14%. There was no correlation between the resistance to prochloraz and the pathogenicity of Fusarium spp. on rice seedlings. The resistant isolates of F. fujikuroi did not show the cross-resistance to other sterol biosynthesis inhibiting fungicides, triflumizole, hexaconazole, difenoconazole and tebuconazole.

• The Korean Journal of Pesticide Science
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• v.14 no.4
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• pp.427-432
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• 2010

Rice bakanae disease caused by Fusarium fujikuroi is one of the most serious rice diseases in Korea. From 2006 to 2009, 118 F. fujikuroi isolates were collected from various regions of rice fields in Korea. Resistance assay of 118 F. fujikuroi isolates to prochloraz, tebuconazole, and benomyl, were performed using agar dilution method. To investigate inhibitory effects of the fungicides, minimum inhibitory concentration of mycelial growth (MIC) and effective concentration inhibiting mycelial growth by 50% ($EC_{50}$) for 118 isolates were calculated using Sigmaplot 8.02 (Antro, SPSS UK, Ltd). Based on the means of $EC_{50}$ values, baseline resistance values were determined as $0.5{\mu}g{\cdot}mL^{-1}$ for prochloraz, $5.0{\mu}g{\cdot}mL^{-1}$ for tebuconazole and $2.5{\mu}g{\cdot}mL^{-1}$ for benomyl. Number of resistant isolates to each fungicide was 17, 19 and 43 for prochloraz, tebuconazole and benomyl, respectively. Furthermore, 4 isolates showed the double resistance to both prochloraz and tebuconazole, 6 isolates to prochloraz and benomyl, and 11 isolates to tebuconazole and benomyl. Isolates CF366 and LF335 isolated from Gyeongbuk province were resistant to the three fungicides tested, prochloraz, tebuconazole and benomyl.

• The Korean Journal of Mycology
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• v.43 no.2
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• pp.112-117
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• 2015

To investigate the changes of the resistance to prochloraz of Fusarium species causing bakanae disease, Fusarium isolates were collected from various regions in Korea, and pathogenicity tests were performed using rice seeds. Minimum inhibitory concentration (MIC) and effective concentration of 50% ($EC_{50}$) values of isolates were determined using the agar dilution method. High frequency distribution of MIC values of prochloraz against isolates collected in 2006~2007 and 2013~2014 years were $3.125{\sim}6.25{\mu}g/mL$ and $6.25{\sim}12.5{\mu}g/mL$, respectively. The mean $EC_{50}$ value of isolates increased from $0.3142{\mu}g/mL$ in 2006~2007 to $0.8124{\mu}g/mL$ in 2013~2014. Based on the $EC_{50}$ value of isolates collected in 2006~2007, the resistant baseline of prochloraz was determined as $0.6{\mu}g/mL$. Compared with the ratio of resistant isolates in 2006~2007, the ratio of resistant isolates in 2013~2014 increased from 6.5% to 41.6%.

• Korean Journal Plant Pathology
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• v.12 no.2
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• pp.226-230
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• 1996

1994~1995년 사이에 대전, 공주, 논산, 부여와 김해 등지에서 채집한 병든 딸기, 토마토, 오이에서 총 1,504 균주의 잿빛곰팡이병균을 분리하여 10 $\mu\textrm{g}$/ml의 약제를 넣은 PDA 배지에서 배양하면서 약제반응을 조사한 결과, benomyl에 대하여는 1,147(76.3%)균주, procymidone에 대하여는 614(40.8%)균주, prochloraz에 대하여는 189(12.6%)균주가 저항성으로 나타났다. UV 처리 및 약제 배지에서의 누대배양을 통하여 prochloraz저항성 균주를 선발하였는데, 이들의 생육 억제 최소 농도(MIC)는 8 $\mu\textrm{g}$/ml 이상이었고, 감수성균의 MIC는 2 $\mu\textrm{g}$/ml 이하였다. 병원력, 포자 발아율, 균핵형성과 같은 적응력과 관련된 생물학적 특성 비교에서 저항성 균주들은 감수성 균주보다 열등하거나 비슷한 정도로 나타났다.

• The Korean Journal of Pesticide Science
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• v.13 no.3
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• pp.171-176
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• 2009

In 2008, 110 isolates of Colletotrichum gloeosporioides were obtained from infected twigs of persimmon collected at Sangju and five fungicides (prochloraz manganese complex, tebuconazole, mancozeb+myclobutanil, fluquinconazole+prochloraz, and tebuconazole+tolyfluanid) were evaluated to determine their growth on fungicide-medium. Among them, the mycelial growth of 97.3 and 98.2% of isolates was inhibited over 91% in response to prochloraz ($250\;{\mu}g/m{\ell}$) and tebuconazole ($125\;{\mu}g/m{\ell}$), respectively, compared to untreated control. In response to mancozeb+myclobutanil, fluquinconazole+prochloraz, and tebuconazole+tolyfluanid, isolates of 96.4, 99.1 and 96.4% of them were inhibited by fungicides, respectively. Isolates showed the highest sensitivity to fluquinconazole+prochloraz among 5 fungicides. The correlation between tebuconazole and tebuconazole+tolyfluanid was higher (r=0.85).

• 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.

• 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.

• 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.

• Research in Plant Disease
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• v.27 no.4
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• pp.164-171
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• 2021

In August 2020, 377 anthracnose strains were isolated from anthracnose-infected peppers collected from 25 farms in Sunchang-gun, Jeollabuk-do. Inhibition rate of mycelial growth of 11 pepper anthracnose fungicides registered in Korea was investigated for 62 strains selected by region and the degree of susceptibility to each fungicide was investigated. As a result of the fungicide susceptibility test of anthracnose to the fungicide, no resistant strains were observed in fluazinam, prochloraz manganese, and benomyl, but resistant strains appeared in at least three areas for other fungicides, and all strains in all regions were resistant to dithianon. Through this, it was confirmed that the fungicide resistance was expressed in the strain group due to the continuous treatment of the fungicide in some areas. By region, resistant strains to seven pesticides appeared in Sunchang-eup and Paldeok-myeon, and resistant strains to six pesticides appeared in Geumgwa-myeon, Bokheung-myeon, Ssangchi-myeon, Yudeung-myeon, and Pungsan-myeon. There was no significant correlation between fungicide registration time and emergence of resistant strains.

• The Korean Journal of Mycology
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• v.43 no.4
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• pp.260-266
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• 2015

To examine the changes in resistance to benomyl of Fusarium species causing bakanae disease, Fusarium isolates were collected in Korea, and pathogenicity tests were performed using rice seeds in vitro. Minimum inhibitory concentration (MIC) and effective concentration of 50% ($EC_{50}$) values of isolates were examined using the agar dilution method. High frequency distribution of MIC values to benomyl against isolates collected in 2006~2007 and 2013~2014 years were $1.5625{\sim}3.125{\mu}g/mL$ and more than $25{\mu}g/mL$, respectively. The mean $EC_{50}$ value of isolates to benomyl increased from $1.6397{\mu}g/mL$ in 2006~2007 to $2.4892{\mu}g/mL$ in 2013~2014. Based on MIC and $EC_{50}$ values of isolates, the moderate resistance of benomyl were determined as more than $25{\mu}g/mL$ of MIC and less $2.4{\mu}g/mL$ of $EC_{50}$ value, and resistant isolates to benomyl were determined as more than $2.4{\mu}g/mL$ of $EC_{50}$ value. Compared with the ratio of resistant isolates in 2006~2007, the ratio of resistance isolates in 2013~2014 increased from 12.5% to 36.4%. In addition, multiple resistant isolates to prochloraz as well as benomyl increased to 20.3% in 2013~2014.