Identification of the G143A Mutation in Cytochrome b Associated with QoI Resistance in Cercospora beticola Isolates from the Red River Valley

Bolton, Melvin D.; Rivera-Varas, Viviana; Secor, Gary A.; Cattanach, A. W.; Metzger, Michael S.

doi:10.1094/php-2013-0812-02-rs

Cited by 11 publications

(5 citation statements)

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“…Importantly, the results of experiment I also identified three isolates from very low, medium, and high EC50 categories that caused similar disease levels on sugar beet. Because C. beticola populations are well known to display considerable variability in disease and other characteristics (2,3,33), the identification of isolates from diverse EC50 categories that caused similar disease allowed us to attribute variation in disease levels in subsequent studies to fungicide treatments and not inherent aggressiveness differences unrelated to fungicide sensitivity.…”

Section: Discussionmentioning

confidence: 99%

“…The use of EC50 to assess field resistance to DMI fungicides appears to be relevant because our results show that an isolate with EC50 values >1.0 ng ml"' caused significantly more disease than isolates with low and medium EC50 values after application of Eminent at full field rates. Although our research focused on CLS in North Dakota and Minnesota, resistance to several fungicide chemistries has occurred woridwide in C. beticola (2,17,(21)(22)(23)25). Sensitivity testing and concomitant fungicide resistance management programs will be necessary to ensure efficacy of all fungicide chemistries for CLS control.…”

Section: Discussionmentioning

confidence: 99%

“…In addition to North Dakota and Minnesota, fungicide resistance in C. beticola has been reported in several sugar-beet-growing regions worldwide (17). Most recently, resistance to strobilurin or quinone outside inhibitor (Qol) fungicides has been reported in Michigan (2).…”

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Efficacy of Variable Tetraconazole Rates Against Cercospora beticola Isolates with Differing In Vitro Sensitivities to DMI Fungicides

et al. 2012

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Bolton, M. D., Rivera-Varas, V., del Rio Mendoza, L. E., Khan, M. F. R., and Secor, G. A. 2012. Efficacy of variable tetraconazole rates against Cercospora beticola isolates with differing in vitro sensitivities to DMI fungicides. Plant Dis. 96:1749-1756.Cercospora leaf spot (CLS) of sugar beet is caused by the fungus Cercospora beticola. CLS management practices include the application of the sterol demethylation inhibitor (DMI) fungicides tetraconazole, difenoconazole, and prothioconazole. Evaluating resistance to DMIs is a major focus for CLS fungicide resistance management. Isolates were collected in 1997 and 1998 (baseline sensitivity to tetraconazole, prothioconazole, or difenoconazole) and 2007 through 2010 from the major sugar-beet-growing regions of Minnesota and North Dakota and assessed for in vitro sensitivity to two or three DMI fungicides. Most (47%) isolates collected in 1997-98 exhibited 50% effective concentration (EC50) values for tetraconazole of <0.01 (Jg ml"', whereas no isolates could be found in this EC50 range in 2010. Since 2007, annual median and mean tetraconazole EC50 values have generally been increasing, and the frequency of isolates with EC50 values >0.11 lig ml-' increased from 2008 to 2010. In contrast, the frequency of isolates with EC50 values for prothioconazole of >1.0 ng mh' has been decreasing since 2007. Annual median difenoconazole EC50 values appears to be stable, although annual mean EC50 values generally have been increasing for this fungicide. Although EC50 values are important for gauging fungicide sensitivity trends, a rigorous comparison of the relationship between in vitro EC50 values and loss of fungicide efficacy in planta has not been conducted for C. beticola. To explore this, 12 isolates exhibiting a wide range of tetraconazole EC50 values were inoculated to sugar beet but no tetraconazole was applied. No relationship was found between isolate EC50 value and disease severity. To assess whether EC50 values are related to fungicide efficacy in planta, sugar beet plants were sprayed with various dilutions of Eminent, the commercial formulation of tetraconazole, and subsequently inoculated with isolates that exhibited very low, medium, or high tetraconazole EC50 values. The high EC50 isolate caused significantly more disease than isolates with medium or very low EC50 values at the field application rate and most reduced rates. Because in vitro sensitivity testing is typically carried out with the active ingredient of the commercial fungicide, we investigated whether loss of disease control was the same for tetraconazole as for the commercial product Eminent. The high EC50 isolate caused more disease on plants treated with tetraconazole than Eminent but disease severity was not different between plants inoculated with the very low EC50 isolate.Cercospora leaf spot (CLS), caused by the fungus Cercospora beticola (Sacc), is the most important foliar disease of sugar beet {Beta vulgaris L.) in North Dakota and Minnesota (39). The disease causes a reduction in root har...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Efficacy of Variable Tetraconazole Rates Against Cercospora beticola Isolates with Differing In Vitro Sensitivities to DMI Fungicides

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“…Since then, tetraconazole and other triazoles have been popular because of protective and curative properties, and low levels of phytotoxicity. Reliance on triazole chemistries for CLS management has become even more pronounced with recent development of resistance to other chemistries including benzimidazole (Weiland and Halloin, 2001) and quinone outside inhibitors (Birla et al, 2012;Bolton et al, 2013a;Bolton et al, 2013b). The reliance on triazoles and the consequent selection pressures imposed by their widespread use has led to a shift in sensitivity in C. beticola populations (Bolton et al, 2012b;Secor et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

RNA-sequencing of Cercospora beticola DMI-sensitive and -resistant isolates after treatment with tetraconazole identifies common and contrasting pathway induction

Bolton

Ebert

Faino

et al. 2016

Fungal Genetics and Biology

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Cercospora beticola causes Cercospora leaf spot of sugar beet. Cercospora leaf spot management measures often include application of the sterol demethylation inhibitor (DMI) class of fungicides. The reliance on DMIs and the consequent selection pressures imposed by their widespread use has led to the emergence of resistance in C. beticola populations. Insight into the molecular basis of tetraconazole resistance may lead to molecular tools to identify DMI-resistant strains for fungicide resistance management programs. Previous work has shown that expression of the gene encoding the DMI target enzyme (CYP51) is generally higher and inducible in DMI-resistant C. beticola field strains. In this study, we extended the molecular basis of DMI resistance in this pathosystem by profiling the transcriptional response of two C. beticola strains contrasting for resistance to tetraconazole. A majority of the genes in the ergosterol biosynthesis pathway were induced to similar levels in both strains with the exception of CbCyp51, which was induced several-fold higher in the DMI-resistant strain. In contrast, a secondary metabolite gene cluster was induced in the resistance strain, but repressed in the sensitive strain. Genes encoding proteins with various cell membrane fortification processes were induced in the resistance strain. Site-directed and ectopic mutants of candidate DMI-resistance genes all resulted in significantly higher EC50 values than the wild-type strain, suggesting that the cell wall and/or membrane modified as a result of the transformation process increased resistance to tetraconazole. Taken together, this study identifies important cell membrane components and provides insight into the molecular events underlying DMI resistance in C. beticola.

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“…Todos los fungicidas QoI están en un grupo de resistencia cruzada entre sí (Heaney et al, 2000;Hnátová et al, 2003;Pasche et al, 2004;Wise et al, 2008Wise et al, , 2009Oliveira et al, 2015). La presencia de la mutación G143A siempre se correlaciona bien con la resistencia cruzada hacia fungicidas QoI (Bolton et al, 2012b;Kim et al, 2003b).…”

Section: Resistencia a Inhibidores De La Quinona Externa (Qois)unclassified

Sensibilidad y resistencia a fungicidas de Cercospora kikuchii, agente causal del tizón de la hoja y mancha púrpura de la semilla de la soja

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En Argentina, diferentes especies de Cercospora causan el tizón de la hoja (TH) y la mancha púrpura de la semilla (MPS) en soja. Debido a que no hay variedades de soja resistentes disponibles en el mercado, el manejo de TH/MPS depende en gran medida de aplicaciones de fungicidas. En este estudio se determinó la sensibilidad de 62 cepas de Cercospora argentinas a fungicidas inhibidores de la desmetilación (DMI), carbamato de metilbenzimidazol (MBC), inhibidores de la quinona externa (QoI), inhibidores de la succinato deshidrogenasa (SDHI) y mancozeb. Todos los aislados fueron sensibles a difenoconazole, epoxiconazole, protioconazole, tebuconazole y cyproconazole (los valores de EC50 variaron de 0,006 a 2,4 µg mL-1). Por el contrario, la mitad (51%) de los aislados fueron sensibles (los valores de EC50 variaron de 0,003 a 0,2 µg mL-1) y la mitad (49%) altamente resistentes (EC50> 100 µg mL-1) a carbendazim. Todos los aislados fueron completamente resistentes a azoxystrobina, trifloxystrobina, pyraclostrobina e insensibles a boscalid, fluxapyroxad y pydiflumetofen (EC50 > 100 µg mL-1). La mutación G143A se detectó en el 82% de los aislados resistentes a QoI y la mutación E198A en el 97% de los aislados resistentes a carbendazim. No se detectaron mutaciones de resistencia aparentes en los genes que codifican para las subunidades B, C y D de la succinato deshidrogenasa. Mancozeb inhibió completamente el crecimiento micelial de los aislados evaluados a 100 µg mL-1. Todos los aislados argentinos de Cercospora fueron sensibles a los fungicidas DMI evaluados, pero se reporta por primera vez resistencia a los fungicidas QoI y MBC. Otro mecanismo(s) además de la modificación del sitio objeto de control del fungicida podrían ser responsable(s) de la resistencia de Cercospora a los fungicidas QoI y MBC. Además, debido a la reciente introducción de fungicidas SDHI en soja en Argentina, se especula que las especies de Cercospora que causan TH/MPS son insensibles (naturalmente resistentes) a este grupo de fungicidas. La insensibilidad debe confirmarse en condiciones de campo.

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Identification of the G143A Mutation in Cytochrome b Associated with QoI Resistance in Cercospora beticola Isolates from the Red River Valley

Cited by 11 publications

References 10 publications

Efficacy of Variable Tetraconazole Rates Against Cercospora beticola Isolates with Differing In Vitro Sensitivities to DMI Fungicides

Efficacy of Variable Tetraconazole Rates Against Cercospora beticola Isolates with Differing In Vitro Sensitivities to DMI Fungicides

RNA-sequencing of Cercospora beticola DMI-sensitive and -resistant isolates after treatment with tetraconazole identifies common and contrasting pathway induction

Sensibilidad y resistencia a fungicidas de <i>Cercospora kikuchii</i>, agente causal del tizón de la hoja y mancha púrpura de la semilla de la soja

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