Trp2027Cys mutation evolves in Digitaria insularis with cross-resistance to ACCase inhibitors

Hudson K Takano; Marcel S C Melo; Ramiro F L Ovejero; Philip H Westra; Todd A Gaines; Franck E Dayan

doi:10.1016/j.pestbp.2019.12.011

Trp2027Cys mutation evolves in Digitaria insularis with cross-resistance to ACCase inhibitors

Pestic Biochem Physiol. 2020 Mar:164:1-6. doi: 10.1016/j.pestbp.2019.12.011. Epub 2019 Dec 28.

Authors

Hudson K Takano¹, Marcel S C Melo², Ramiro F L Ovejero³, Philip H Westra⁴, Todd A Gaines⁵, Franck E Dayan⁶

Affiliations

¹ Department of Bioagricultural Sciences and Pest Management, Colorado State University, 300 W Pitkin St., Fort Collins, CO 80523, USA. Electronic address: Hudson.Takano@colostate.edu.
² Bayer CropScience, 12901 Nações Unidas Ave., São Paulo, SP 04578-000, Brazil. Electronic address: Marcel.Melo@bayer.com.
³ Bayer CropScience, 12901 Nações Unidas Ave., São Paulo, SP 04578-000, Brazil. Electronic address: Ramiro.Ovejero@bayer.com.
⁴ Department of Bioagricultural Sciences and Pest Management, Colorado State University, 300 W Pitkin St., Fort Collins, CO 80523, USA. Electronic address: Philip.Westra@colostate.edu.
⁵ Department of Bioagricultural Sciences and Pest Management, Colorado State University, 300 W Pitkin St., Fort Collins, CO 80523, USA. Electronic address: Todd.Gaines@colostate.edu.
⁶ Department of Bioagricultural Sciences and Pest Management, Colorado State University, 300 W Pitkin St., Fort Collins, CO 80523, USA. Electronic address: Franck.Dayan@colostate.edu.

PMID: 32284114
DOI: 10.1016/j.pestbp.2019.12.011

Abstract

Sourgrass (Digitaria insularis) is one of the most problematic weeds in South America because glyphosate resistance is widespread across most crop production regions. Acetyl coenzyme A carboxylase (ACCase)-inhibiting herbicides have been intensively used to manage D. insularis, which substantially increased selection pressure for this class of herbicides. We confirmed resistance to ACCase herbicides in a D. insularis population from Brazil and characterized its molecular basis. Resistant plants showed high level of resistance to haloxyfop (resistance factor, RF = 613-fold), low level of resistance to pinoxaden (RF = 3.6-fold), and no resistance to clethodim. A target-site mutation, Trp2027Cys, was found in the ACCase sequence from resistant plants. A protein homology model shows that the Trp2027Cys mutation is near the herbicide-binding pocket formed between two ACCase chains, and is predicted to obstruct the access of aryloxyphenoxypropionates (FOP) herbicides to the binding site. A qPCR-based single nucleotide polymorphism genotyping method was validated to discriminate susceptible (wild-type Trp2027) and resistant (mutant Cys2027) alleles. All resistant plants were homozygous for the mutation and the assay could be used for early detection of resistance in D. insularis field samples with suspected resistance to ACCase inhibitors.

Keywords: Aryloxyphenoxypropionates; Cyclohexanediones; Phenylpyrazoline; Protein homology modeling; Target-site resistance.

MeSH terms

Acetyl-CoA Carboxylase
Brazil
Digitaria*
Herbicide Resistance
Herbicides*
Mutation
Poaceae

Substances

Herbicides
Acetyl-CoA Carboxylase