Reduced sensitivity to fenarimol in Japanese field strains of<i>Venturia nashicola</i>

Tomita, Yasunori; Ishii, Hideo

doi:10.1002/(sici)1096-9063(1998100)54:2<150::aid-ps797>3.0.co;2-a

Pestic. Sci.

1998

DOI: 10.1002/(sici)1096-9063(1998100)54:2<150::aid-ps797>3.0.co;2-a

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Reduced sensitivity to fenarimol in Japanese field strains ofVenturia nashicola

Yasunori Tomita¹,

Hideo Ishii

Abstract: Monoconidial strains of Venturia nashicola Tanaka et Yamamoto were isolated from Japanese or Chinese white pear trees which had never been treated with sterol demethylation inhibitors (DMIs) and their baseline sensitivities to fenarimol were determined by mycelial growth tests on fungicide‐amended culture media. Strains were also obtained from Japanese pear orchards, which had been intensively treated with DMIs for several years and monitored for the shifts of fenarimol sensitivity in comparison with the basel… Show more

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Cited by 9 publications

References 10 publications

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Cloning and Sequence Analysis of the Eburicol 14 α‐Demethylase Encoding Gene (CYP51) from the Japanese Pear Scab Fungus Venturia nashicola

Cools¹,

Ishii²,

Butters³

et al. 2002

Journal of Phytopathology

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The slow growth of many filamentous fungi in vitro prevents rapid isolation of large quantities of genomic DNA, thereby hampering molecular studies. Using a polymerase chain reaction (PCR)-based adapter ligation cloning technique that requires only nanogram quantities of genomic DNA we have successfully cloned the complete CYP51 gene encoding the eburicol 14a-demethylase, the target for DMI (Demethylationinhibiting) 2 fungicides, from the Japanese pear scab fungus, Venturia nashicola. Analysis of predicted amino acid sequences of CYP51s from strains less sensitive to DMIs revealed no alterations when compared to the sensitive reference strain. U. S.

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Cloning and Sequence Analysis of the Eburicol 14 α‐Demethylase Encoding Gene (CYP51) from the Japanese Pear Scab Fungus Venturia nashicola

Cools¹,

Ishii²,

Butters³

et al. 2002

Journal of Phytopathology

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Resistance to Mefenoxam and Metalaxyl Among Field Isolates of Phytophthora capsici Causing Phytophthora Blight of Bell Pepper

2001

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Incidence of Phytophthora blight in bell pepper fields that were sprayed for the first time with Ridomil Gold (mefenoxam) according to labeled recommendations was higher in North Carolina in 1997 than in previous years. Mefenoxam is the more active enantiomer contained in the racemic fungicide metalaxyl. A total of 150 isolates were obtained from 17 fields at eight grower locations. Among isolates from all locations, 30% were classified as sensitive, 10% as intermediate, and 59% were resistant to mefenoxam. Mefenoxam-resistant isolates were found in 82% of the fields sampled (14 of 17 fields). The proportion of resistant isolates in individual (fields ranged from 28 to 100%. The mean effective concentration (EC50) values for mefenoxam-sensitive isolates was 0.568 μg ml-1 (ranging from 0.12 to 1.1 μg ml-1), whereas the mean EC50 value for mefenoxam-resistant isolates was 366.5 μg ml-1 (ranging from 3 to 863 μg ml-1). The mean EC50 value for metalaxyl-sensitive isolates was 0.27 μg ml-1 (ranging from 0.00002 to 1.3 μg ml-1) and for metalaxyl-resistant isolates was 470.34 μg ml-1 (ranging from 10 to 966 μg ml-1). The greatest proportion of resistant isolates came from fields where mefenoxam was used alone rather than in combination with other fungicides. Both mating types were found among resistant isolates, suggesting that these isolates may persist in soil in subsequent years. Field isolates of Phytophthora capsici resistant to mefenoxam on pepper have not been reported previously and now pose new challenges for management of this important disease.

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DMI-Fungicide Resistance in Venturia nashicola, the Causal Agent of Asian Pear Scab—How Reliable Are Mycelial Growth Tests in Culture?

et al. 2021

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Scab, caused by Venturia nashicola, is among the most serious diseases of Asian pears and control of this disease largely relies on sterol demethylation inhibitor (DMI) fungicides. However, pear growers have complained about field performance of DMIs since the mid-2000s. In this study, to evaluate pathogen sensitivity, mycelial growth tests and inoculation tests were conducted using DMI-amended culture medium and fungicide-sprayed potted pear trees, respectively. Results confirmed distribution of isolates resistant to fenarimol, hexaconazole, and difenoconazole in the field populations. Importantly, results from tests in culture did not fully correlate with those from tests in planta. Due to phenotypic instability of resistance and poor sporulation of this pathogen in culture, resistance is generally assessed by laborious and time-consuming inoculation with conidia collected from a field. To improve the result interpretation from in vitro tests, the isolates were genotyped: the CYP51 gene which encodes the target sterol 14α-demethylase was sequenced and various mutations have been detected in the coding sequence of DMI-resistant isolates. In addition to the detected single nucleotide polymorphisms, alternative mechanisms, not based on changes in the structure of the target protein, may also increase DMI resistance. Development of molecular methods for the diagnosis of DMI resistance seems to be challenging in V. nashicola.

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Reduced sensitivity to fenarimol in Japanese field strains ofVenturia nashicola

Cited by 9 publications

References 10 publications

Cloning and Sequence Analysis of the Eburicol 14 α‐Demethylase Encoding Gene (CYP51) from the Japanese Pear Scab Fungus Venturia nashicola

Cloning and Sequence Analysis of the Eburicol 14 α‐Demethylase Encoding Gene (CYP51) from the Japanese Pear Scab Fungus Venturia nashicola

Resistance to Mefenoxam and Metalaxyl Among Field Isolates of Phytophthora capsici Causing Phytophthora Blight of Bell Pepper

DMI-Fungicide Resistance in Venturia nashicola, the Causal Agent of Asian Pear Scab—How Reliable Are Mycelial Growth Tests in Culture?

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