<i>Cytochrome b</i> Mutations F129L and G143A Confer Resistance to Azoxystrobin in <i>Cercospora nicotianae</i>, the Frogeye Leaf Spot Pathogen of Tobacco

Dixon, Ed; Barlow, William B.; Walles, Grant; Amsden, B.; Hirsch, Robert; Pearce, Robert C.; Pfeufer, Emily E.

doi:10.1094/pdis-02-19-0382-re

Cited by 12 publications

(4 citation statements)

References 22 publications

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“…Dixon et al . (2020) reported that mutations F129L and G143A conferred resistance to azoxystrobin in C. nicotianae , the causal agent of frogeye leaf spot of tobacco. Imazaki et al .…”

Section: Introductionmentioning

confidence: 99%

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

et al. 2020

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Cercospora species cause cercospora leaf blight (CLB) and purple seed stain (PSS) on soybean. Because there are few resistant soybean varieties available, CLB/PSS management relies heavily upon fungicide applications. Sensitivity of 62 Argentinian Cercospora isolates to demethylation inhibitor (DMI), methyl benzimidazole carbamate (MBC), quinone outside inhibitor (QoI), succinate dehydrogenase inhibitor (SDHI) fungicides, and mancozeb was determined in this study. All isolates were sensitive to difenoconazole, epoxiconazole, prothioconazole, tebuconazole, and cyproconazole (EC50 values ranged from 0.006 to 2.4 µg/ml). In contrast, 51% of the tested isolates were sensitive (EC50 values ranged from 0.003 to 0.2 µg/ml), and 49% were highly resistant (EC50 > 100 µg/ml) to carbendazim. Interestingly, all isolates were completely resistant to azoxystrobin, trifloxystrobin, and pyraclostrobin, and insensitive to boscalid, fluxapyroxad, and pydiflumetofen (EC50 > 100 µg/ml). The G143A mutation was detected in 82% (53) of the QoI‐resistant isolates and the E198A mutation in 97% (31) of the carbendazim‐resistant isolates. No apparent resistance mutations were detected in the succinate dehydrogenase genes (subunits sdhB, sdhC, and sdhD). Mancozeb completely inhibited mycelial growth of the isolates evaluated at a concentration of 100 µg/ml. All Argentinian Cercospora isolates were sensitive to the DMI fungicides tested, but we report for the first time resistance to QoI and MBC fungicides. Mechanism(s) other than fungicide target‐site modification may be responsible for resistance of Cercospora to QoI and MBC fungicides. Moreover, based on our results and on the recent introduction of SDHI fungicides on soybean in Argentina, Cercospora species causing CLB/PSS are insensitive (naturally resistant) to SDHI fungicides. Insensitivity must be confirmed under field conditions.

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“…Dixon et al . (2020) reported that mutations F129L and G143A conferred resistance to azoxystrobin in C. nicotianae , the causal agent of frogeye leaf spot of tobacco. Imazaki et al .…”

Section: Introductionmentioning

confidence: 99%

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

et al. 2020

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“…Several PCR‐based molecular procedures have been developed to test the existence of G143A mutation of Cyt‐b gene as a marker to monitor QoI resistance (Shrestha et al, 2020). But other point mutations in the Cyt‐b gene associated with QoI resistance have been reported (Dixon et al, 2020). Moreover, there may be another unrevealed mechanism that confers QoI resistance.…”

Section: Discussionmentioning

confidence: 99%

“…Currently, QoI-resistant strains of C. beticola were found in the United States (Bolton et al, 2013), Canada (Trueman et al, 2013), Slovakia (Hudec et al, 2020), Japan (Kayamori et al, 2020) and Serbia (Balandžić et al, 2020). Previous reports also demonstrated that resistance to QoI was attributed to a point mutation in Cyt-b gene, including the amino acid substitution of alanine for glycine at codon 143 (G143A), the substitution of phenylalanine with leucine at codon 129 (F129L) or substitution of glycine with arginine at codon 143 (G143R) (Bolton et al, 2013;Ma et al, 2018;Dixon et al, 2020). In China, CLS is a severe disease of sugar beet and is currently controlled by triphenyltin acetate, benzimidazole, DMI and QoI fungicides.…”

Section: Introductionmentioning

confidence: 99%

A new method for single spore isolation and fungicide resistance monitoring of Cercospora beticola, and the first report of QoI‐resistant isolates with G143A or F129L mutations of the CbCyt b gene in China

Liu

Dong

et al. 2022

Journal of Phytopathology

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Cercospora leaf spot (CLS) caused by Cercospora beticola is the most destructive foliar disease of sugar beet worldwide and is mainly controlled by timely fungicide applications. Recently, CLS control by pyraclostrobin exhibited significantly reduced efficiency in some fields of the Chifeng area in Inner Mongolia Autonomous Region of China. Purification of fungi by single spore isolation is essential for the study of fungal and fungicide resistance. However, the conventional single spore isolation and fungicide sensitivity assay for C. beticola are time‐consuming with a risk of contamination. We developed a new method for single spore isolation of C. beticola, which facilitated monitoring fungicide sensitivity of infected field samples. First, the composite spore suspension was prepared from typical lesions by vortex in the sterilized centrifuge tube. Then, the diluted spore suspension was spread on the streptomycin‐amended potato dextrose agar (PDA) plate or the PDA plate contained a threshold dosage of specific fungicide. The C. beticola colony derived from a single spore could be observed with naked eye and easily isolated by a sterilized scalpel knife after 36 h of incubation at 25°C. Meanwhile, the percentage of fungicide‐resistant or ‐tolerant isolates could be analysed based on the growth of different PDA media within 3 days. Based on this method, we identified that 22.88% of the C. beticola isolates were resistant to pyraclostrobin in the Chifeng area, indicating a high risk of emergence of C. beticola‐resistant strains to QoI fungicides in this area. Furthermore, the G143A or F129L mutation of the cytochrome b (Cyt‐b) gene was found in these resistant isolates. To our knowledge, this is the first report of C. beticola QoI‐resistant isolates with G143A or F129L mutation of CbCyt‐b gene in China. Our approach provides considerable potential for studying the biology, fitness and fungicide resistance of C. beticola.

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“…For example, QoI fungicide resistance, based on the G143A mutation in Cytb , also has been detected in Cercospora sojina , 27 Cercospora cf. flagellaris , 41 Cercospora nicotianae , 42,43 Cercospra kikuchii , 42,44,45 Corynespora cassiicola 17 and Colletotrichum truncatum , 45 probably owing to the intensive use of QoIs for soybean production. Therefore, the incorporation of metyltetraprole into the soybean disease protection program could be beneficial for soybean growers.…”

Section: Discussionmentioning

confidence: 99%

Microtiter plate test using liquid medium is an alternative method for monitoring metyltetraprole sensitivity in Cercospora beticola

Matsuzaki

Uda

Kurahashi

et al. 2020

Pest Management Science

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BACKGROUND Metyltetraprole is a new quinone outside inhibitor (QoI) fungicide showing potent activity against QoI‐resistant fungi that possess the G143A cytochrome b mutation, which confers resistance to existing QoIs such as trifloxystrobin. For its sustainable use, monitoring of metyltetraprole sensitivity is necessary and the establishment of appropriate methodology is important in each pathogen species. RESULTS In Cercospora beticola, the causal agent of sugar beet leaf spot, some isolates were less sensitive to metyltetraprole (EC50 > 1 mg L–1, higher than the saturated concentration) using the common agar plate method, even with 100 mg L−1 salicylhydroxamic acid, an alternative oxidase inhibitor. However, microtiter tests (EC50 < 0.01 mg L−1), conidial germination tests (EC50 < 0.01 mg L−1) and in planta tests (>80% control at 75 mg L−1 run‐off spraying) confirmed that all tested isolates were highly sensitive to metyltetraprole. For trifloxystrobin, G143A mutants were clearly resistant upon microtiter plate tests (median EC50 > 2 mg L−1) and distinct from wild‐type isolates (median EC50 < 0.01 mg L−1). Notably, mycelium fragments were usable for the microtiter plate tests and the test was applicable for isolates that do not form sufficient conidia. Our monitoring study by microtiter plate tests did not indicate the presence of metyltetraprole‐resistant C. beticola isolates in populations in Hokkaido, Japan. CONCLUSION The microtiter tests were revealed to be useful for monitoring the sensitivity of C. beticola to metyltetraprole and trifloxystrobin. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

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Cytochrome b Mutations F129L and G143A Confer Resistance to Azoxystrobin in Cercospora nicotianae, the Frogeye Leaf Spot Pathogen of Tobacco

Cited by 12 publications

References 22 publications

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

Fungicide resistance in Cercospora species causing cercospora leaf blight and purple seed stain of soybean in Argentina

A new method for single spore isolation and fungicide resistance monitoring of Cercospora beticola, and the first report of QoI‐resistant isolates with G143A or F129L mutations of the CbCyt b gene in China

Microtiter plate test using liquid medium is an alternative method for monitoring metyltetraprole sensitivity in Cercospora beticola

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