Baseline Sensitivity and Cross-Resistance to Succinate-Dehydrogenase-Inhibiting and Demethylation-Inhibiting Fungicides in <i>Didymella bryoniae</i>

Thomas, Anna; Langston, David B.; Stevenson, K. L.

doi:10.1094/pdis-09-11-0744-re

Cited by 65 publications

(45 citation statements)

References 33 publications

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“…The relatively small ranges and resistance factors for cyprodinil and fludioxonil for isolates of D. bryoniae that never were exposed to these fungicides was similar to the ranges (0.03 to 0.25) and resistance factors (2.7 to 14.2) for D. bryoniae isolates never exposed to boscalid or difenoconazole (Keinath 2009;Keinath and Hansen 2013;Thomas et al 2012b). The ranges for baseline isolates from South Carolina and other states tested for sensitivity to azoxystrobin and tebuconazole were 10 and 19 times greater, respectively, than the range for cyprodinil (Keinath 2008;Keinath and Hansen 2013).…”

Section: Discussionsupporting

confidence: 61%

Baseline Sensitivity of Didymella bryoniae to Cyprodinil and Fludioxonil and Field Efficacy of these Fungicides Against Isolates Resistant to Pyraclostrobin and Boscalid

Keinath

2015

Plant Disease

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Section: Discussionsupporting

confidence: 61%

Baseline Sensitivity of Didymella bryoniae to Cyprodinil and Fludioxonil and Field Efficacy of these Fungicides Against Isolates Resistant to Pyraclostrobin and Boscalid

Keinath

2015

Plant Disease

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“…In all, 20 to 24 isolates of D. bryoniae were collected from each treatment (4 per replication) and tested for sensitivity to boscalid, tebuconazole, difenoconazole, thiophanate methyl, and azoxystrobin using an in vitro mycelial growth assay as described below. A discriminatory concentrafion of 3.0 |ag/ml was used for boscalid (23), tebuconazole, and difenoconazole (25) and 100 |ig/ml was used for thiophanate-methyl (9).…”

Section: Methodsmentioning

confidence: 99%

“…Relative germination was calculated as the percent germinafion on fungicide-amended medium divided by the percent germination on nonamended medium. An isolate was considered resistant if the relative germinafion on fungicide-amended medium was greater than 0.5 (25).…”

Section: Methodsmentioning

confidence: 99%

“…Reduced sensitivity to DMI fungicides has been reported in many fungal pathogens (3,11,14,17). Tebuconazole and difenoconazole belong to the same chemical group of triazoles within the DMI class and we have shown that there is potential for cross-resistance between these two fungicides based on a significant correlation between 50% effective concentration (EC50) values of sensitive isolates (25).…”

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confidence: 99%

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Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

et al. 2012

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Thomas, A., Langston, D. B., Jr., Sanders, H. F., and Stevenson, K. L. 2012. Relationship between fungicide sensitivity and control of gummy stem blight of watermelon under field conditions. Plant Dis. 96:1780-1784.Gummy stem blight (GSB), caused by the fungus Didymella bryoniae, is the most destructive disease of watermelon and is managed primarily with fungicides. D. bryoniae has developed resistance to many fungicides that were once very effective, including azoxystrobin, boscalid, and thiophanate-methyl. Field experiments were conducted in Tifton (TN) and Reidsville (RV), GA in 2009 and 2010 to establish a relationship between frequency of resistance to a fungicide based on in vitro assays and its efficacy in the management of GSB. Frequency of resistance to boscalid, thiophanate-methyl, and azoxystrobin was >0.80 in isolates collected from nontreated plots in both locations and years. All isolates collected after six applications of boscalid, thiophanatemethyl, or azoxystrobin were resistant to the respective fungicide. All isolates collected from treated and nontreated plots were sensitive to tebuconazole and difenoconazole. GSB severity was assessed on a weekly basis from 63 days after planting. GSB severity in plots treated with boscalid, thiophanate-methyl, or azoxystrobin was not significantly different from that in the nontreated plots (39%, TN-2009; 45%, TN-2010; and 16%, RV-2010). GSB severity in tebuconazole-treated plots (27%, TN-2009; 14%, TN-2010; and 4%, RV-2010) was significantly lower than all other treatments and the nontreated control. There was a consistent negative association between frequency of fungicide resistance and disease control in the field. Thus, knowledge of the frequency of fungicide resistance in the pathogen population will be helpful in selecting the most effective fungicides for the management of GSB in watermelon fields.

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“…However, these values were higher than those previously reported for Didymella bryoniae, closely related species. Thomas et al [26] obtained EC 50 values for this species ranging from 0.062 to 0.385 mg L ¡1 for the isolates collected in Georgia in 2001 and 2002, while …”

Section: Discussionmentioning

confidence: 99%

Toxicity of copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin toDidymella applanataisolates from Serbia

Mirković

Tanović

Hrustić

et al. 2015

Journal of Environmental Science and Health, Part B

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A study of the in vitro sensitivity of 10 isolates of Didymella applanata to copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin, was conducted. The isolates were derived from diseased raspberry canes sampled during 2013 at five localities in western part of Serbia, known as the main raspberry growing region of the country. Prior to sensitivity testing experimental conditions for radial growth assay were optimized. The results showed that the temperature of 22 °C, oatmeal agar medium and 12/12 hrs light/ darkness light regimen provided the best conditions for sensitivity tests. Most of D. applanata isolates were sensitive to the tested fungicides. The narrowest range of EC50 values was recorded for tebuconazole (1.42-2.66 mg L(-1)). The widest range of EC50 values was obtained for pyraclostrobin, ranging from 0.17 mg L(-1) to 55.33 mg L(-1). The EC50 values for the studied isolates were 39.48-51.19 mg L(-1) for copper hydroxide, 12.12-18.73 mg L(-1) for dithianon and 5.72-42.56 mg L(-1) for fluazinam. According to resistance factor values, all D. applanata isolates were sensitive to copper hydroxide, dithianon and tebuconazole. Among tested isolates, six were highly resistant to pyraclostrobin (RFs in the range of 207.1-325.5) and two moderately resistant to fluazinam (RFs were 3 and 7.4), respectively.

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Baseline Sensitivity and Cross-Resistance to Succinate-Dehydrogenase-Inhibiting and Demethylation-Inhibiting Fungicides in Didymella bryoniae

Cited by 65 publications

References 33 publications

Baseline Sensitivity of Didymella bryoniae to Cyprodinil and Fludioxonil and Field Efficacy of these Fungicides Against Isolates Resistant to Pyraclostrobin and Boscalid

Baseline Sensitivity of Didymella bryoniae to Cyprodinil and Fludioxonil and Field Efficacy of these Fungicides Against Isolates Resistant to Pyraclostrobin and Boscalid

Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

Toxicity of copper hydroxide, dithianon, fluazinam, tebuconazole and pyraclostrobin toDidymella applanataisolates from Serbia

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