Pest Management Science (2016) 72, 1673-1680

Rafael M. Pedroso, Kassim Al-Khatib, Rocio Alarcón-Reverte and Albert J. Fischer (2016)
A psbA mutation (Val₂₁₉ to Ile) causes resistance to propanil and increased susceptibility to bentazon in Cyperus difformis
Pest Management Science 72 (9), 1673-1680
Abstract:
BACKGROUND
Propanil-resistant (R) Cyperus difformis populations were recently confirmed in California rice fields. To date, propanil resistance in other weed species has been associated with enhanced aryl acylamidase (AAA)-mediated propanil conversion into 3,4-dichloroaniline. Our objectives were to determine the level of propanil resistance and cross-resistance to other PSII inhibitors in C. difformis lines, and to elucidate the mechanism of propanil resistance.
RESULTS
The propanil-R line had a 14-fold propanil resistance and increased resistance to bromoxynil, diuron and metribuzin, but not to atrazine. The R line, however, displayed a fourfold increased susceptibility to bentazon. Interestingly, susceptible (S) plants accumulated more 3,4-dichloroaniline and were more injured by propanil and carbaryl (AAA-inhibitor) applications than R plants, suggesting that propanil metabolism is not the resistance mechanism. psbA gene sequence analysis indicated a valine-219–isoleucine (Val₂₁₉Ile) amino acid exchange in the propanil-R chloroplast D1 protein.
CONCLUSION
The D1 Val₂₁₉Ile modification in C. difformis causes resistance to propanil, diuron, metribuzin and bromoxynil but increased susceptibility to bentazon, suggesting that the Val219 residue participates in binding of these herbicides. This is the first report of a higher plant exhibiting target-site propanil resistance. Tank mixing of bentazon and propanil, where permitted, can control both propanil-R and propanil-S C. difformis and prevent the spread of the resistant phenotype.
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Link to article at publishers website
Database assignments for author(s): Kassim Al-Khatib, Rafael Munhoz Pedroso, Albert J. Fischer

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.
	Cyperus difformis (weed)	Rice (Oryza)	U.S.A. (SW)