Resistance mechanism to carboxylic acid amide fungicides in the cucurbit downy mildew pathogen Pseudoperonospora cubensis

2011 ◽  
Vol 67 (10) ◽  
pp. 1211-1214 ◽  
Author(s):  
Mathias Blum ◽  
Maya Waldner ◽  
Gilberto Olaya ◽  
Yigal Cohen ◽  
Ulrich Gisi ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Downy Mildew ◽  
Acid Amide ◽  
Resistance Mechanism ◽  
Pseudoperonospora Cubensis ◽  
Carboxylic Acid Amide ◽  
Cucurbit Downy Mildew

scholarly journals First Report of Carboxylic Acid Amide Fungicide Resistance in Plasmopara viticola (Grapevine Downy Mildew) in North America

2018 ◽  
Vol 19 (2) ◽  
pp. 139-139 ◽  
Author(s):  
Xuewen Feng ◽  
Anton Baudoin
Keyword(s):  
North Carolina ◽  
Carboxylic Acid ◽  
North America ◽  
Downy Mildew ◽  
Acid Amide ◽  
Plasmopara Viticola ◽  
Carboxylic Acid Amide ◽  
Grapevine Downy Mildew ◽  
Grape Downy Mildew ◽  
Caa Fungicides

This report documents the first known occurrence in North America of resistance in grape downy mildew (Plasmopara viticola) to the carboxylic acid amide (CAA) fungicides mandipropamid and dimethomorph. These fungicides (FRAC group 40) have been an important component of downy mildew management programs for the past decade. Resistant isolates were obtained at three locations in Virginia and one in North Carolina, at considerable distances from each other. Resistance was documented by bioassay and the presence of the G1105S mutation, which has been associated with CAA resistance of P. viticola in other areas. Further survey is needed to determine the geographic extent of this resistance.

scholarly journals Detection and Characterization of Carboxylic Acid Amide-Resistant Plasmopara viticola in China Using a TaqMan-MGB Real-Time PCR

Plant Disease ◽  
2020 ◽  
Vol 104 (9) ◽  
pp. 2338-2345
Author(s):  
Xiaoqing Huang ◽  
Xina Wang ◽  
Fanfang Kong ◽  
Theo van der Lee ◽  
Zhongyue Wang ◽  
...  
Keyword(s):  
Carboxylic Acid ◽  
Real Time ◽  
Downy Mildew ◽  
Real Time Pcr ◽  
Fungicide Resistance ◽  
Management Strategies ◽  
Acid Amide ◽  
Plasmopara Viticola ◽  
Carboxylic Acid Amide ◽  
Caa Fungicides

Grape production is increasing globally and so are problems with downy mildew, one of the main constraints in grape production. Downy mildew on grape is caused by Plasmopara viticola, an obligate biotrophic pathogen belonging to the oomycetes. Control of the disease is usually performed by fungicide applications, of which carboxylic acid amide (CAA) fungicides represent one of the most widely used groups of fungicides. Our previous research showed that the extensive application of CAA fungicides can result in fungicide resistance and in China, CAA-resistant isolates of P. viticola were collected from the field in 2014. To monitor the distribution and spread of CAA fungicide resistance, we developed a TaqMan-minor groove binder (MGB) real-time PCR-based method designed on a functional mutation in the PvCesA3 gene that allows efficient identification of CAA fungicide resistant and sensitive genotypes. The assay was validated on 50 isolates using Sanger sequencing and fungicide bioassays and exploited in a comprehensive survey comprising 2,227 single-sporangiophore isolates from eight major grapevine regions in China. We demonstrate that CAA fungicide resistance in P. viticola is widespread in China. On average, 53.3% of the isolates were found to be resistant, but marked differences were found between locations with percentages of resistant isolates varying from 0.3 to 96.6%. Furthermore, the frequency of CAA-resistant isolates was found to be significantly correlated with the exposure to CAA fungicides (P < 0.05). We further discussed the possibilities to apply the TaqMan-MGB real-time PCR assay to assess the frequency of fungicide-resistant P. viticola isolates in each region or vineyard, which would facilitate the correct choice of fungicide for grape downy mildew and resistance management strategies.

Fungicide efficacy against Pseudoperonospora humuli and point-mutations linked to carboxylic acid amide (CAA) resistance in Michigan.

Plant Disease ◽  
2020 ◽  
Author(s):  
Douglas S Higgins ◽  
Timothy D Miles ◽  
Mary Hausbeck
Keyword(s):  
Carboxylic Acid ◽  
Downy Mildew ◽  
Disease Severity ◽  
Acid Amide ◽  
Point Mutations ◽  
Management Program ◽  
Eastern United States ◽  
Carboxylic Acid Amide ◽  
Progress Curve ◽  
Pseudoperonospora Humuli

Hops have expanded as a niche crop in Michigan and other production areas in the eastern United States, but growers in these regions face annual downy mildew outbreaks incited by Pseudoperonospora humuli, exacerbated by frequent rainfall and high relative humidity. We evaluated the efficacy of foliar- and drench-applied fungicides against downy mildew and examined Michigan isolates for point mutations linked to carboxylic acid amide (CAA) resistance. Disease severity and density were assessed weekly in 2016 and 2017 in non-trellised research hop yards in Michigan. Area under the disease progress curve values for disease severity were significantly lower for plants treated with oxathiapiprolin, ametoctradin/dimethomorph, fluopicolide, cyazofamid, or mandipropamid (90.6 to 100% control) compared to those treated with fosetyl-Al (64.3 to 93.0% control) at both locations for both years. Drench treatments of fluopicolide and oxathiapiprolin/ mefenoxam reduced disease density and severity at both locations but were only moderately effective (76.4 to 91.5% control). To assess CAA resistance, the CesA3 gene was aligned using reference downy mildew species and primers designed to amplify the 1105 and 1109 amino acids. Point mutations conferring CAA resistance were not detected at these loci for sporangia from 42 symptomatic shoots collected from 11 commercial hop yards. These efficacy results for hop downy mildew are needed to guide disease recommendations in this expanding Michigan industry. The absence resistant genotypes indicate that Michigan growers can continue to utilize CAA-containing commercial fungicides as part of an overall downy mildew management program.

scholarly journals Fungicides for Control of Downy Mildew on Pickling Cucumber in Michigan

2019 ◽  
Vol 20 (3) ◽  
pp. 165-169 ◽  
Author(s):  
Katelyn E. Goldenhar ◽  
Mary K. Hausbeck
Keyword(s):  
Downy Mildew ◽  
Untreated Control ◽  
Field Studies ◽  
Pseudoperonospora Cubensis ◽  
Relative Area ◽  
Disease Progress Curve ◽  
Cucurbit Downy Mildew ◽  
Disease Progress ◽  
Pickling Cucumber ◽  
Progress Curve

Michigan growers rely on fungicides to limit cucurbit downy mildew (CDM), incited by Pseudoperonospora cubensis; resistance of the pathogen to fungicides is a concern. We evaluated fungicides against CDM in Michigan field studies from 2015 to 2017. According to the relative area under the disease progress curve (rAUDPC), in 2015, mandipropamid, propamocarb, fluxapyroxad/pyraclostrobin, copper octanoate, and dimethomorph resulted in disease levels similar to the control. These treatments, along with cymoxanil, were similar to the control in 2016. Fungicides that were ineffective during 2015 and 2016 did not limit CDM in 2017. Famoxadone/cymoxanil and fluopicolide did not limit CDM in 2017. Each year, the following treatments were similar for disease based on rAUDPC data: oxathiapiprolin applied alone or premixed with chlorothalonil or mandipropamid, ametoctradin/dimethomorph, fluazinam, mancozeb/zoxamide, cyazofamid, and ethaboxam. An exception occurred in 2017, when ethaboxam was less effective than fluazinam, oxathiapiprolin/chlorothalonil, and oxathiapiprolin/mandipropamid. Mancozeb and chlorothalonil treatments were similar in 2015 and 2017, according to rAUDPC data. In 2017, yields were increased for oxathiapiprolin/chlorothalonil, oxathiapiprolin/mandipropamid, mancozeb, ametoctradin/dimethomorph, mancozeb/zoxamide, ethaboxam, cyazofamid, chlorothalonil, and fluazinam compared with the untreated control.

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