Pest Management Science (2019) 75, 2115-2123

Séverine Fontaine, Florent Remuson, Laëtitia Caddoux and Benoit Barrès (2019)
Investigation of the sensitivity of Plasmopara viticola to amisulbrom and ametoctradin in French vineyards using bioassays and molecular tools
Pest Management Science 75 (8), 2115-2123
Abstract:
BACKGROUND
Complex III inhibitors are key compounds in the control of Plasmopara viticola. They are prone to the development of resistance, as demonstrated by the emergence of resistance to quinone-outside inhibitors. By using a combination of bioassays and molecular methods, we monitored sensitivity to amisulbrom and ametoctradin in P. viticola populations in French vineyards from 2012 to 2017.
RESULTS
We found that the alternative oxidase (AOX)-related resistance mechanism was common in French P. viticola populations. Target-site resistance to ametoctradin was first detected in 2015 and is likely caused by a single point mutation in the cytochrome b gene, leading to the S34L substitution. The role of this substitution in resistance to ametoctradin was corroborated by another study using an experimental model. A molecular biology method has been developed to detect the mutant allele. To date, the frequency of this mutation is low in French P. viticola populations and it is often co-detected with the wild-type allele.
CONCLUSION
Populations of P. viticola displaying evidence of AOX-related resistance were detected for every surveyed year, and their occurrence in French vineyards seems to be increasing over time. This resistance mechanism is currently threatening the efficacy of complex III inhibitors in the field. The low frequency of the S34L allele conferring resistance to ametoctradin, and the instability of resistant phenotypes in some populations, suggest that a fitness cost may be associated with the mutation.
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Link to article at publishers website

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Plasmopara viticola	Grapevine (Vitis)	France