First report of target-site resistance to ACCase-inhibiting herbicides in Bromus tectorum L.

Victor Hugo Vidal Ribeiro, Caio A.C.G. Brunharo, Carol Mallory-Smith, Darrin L. Walenta, Judit Barroso

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3 Scopus citations


Background: The prevalent and repeated use of acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides for Bromus tectorum L. control in fine fescue (Festuca L. spp) grown for seed has selected ACCase-resistant B. tectorum populations. The objectives of this study were to (1) evaluate the response of nine B. tectorum populations to the ACCase inhibitors clethodim, sethoxydim, fluazifop-P-butyl, and quizalofop-P-ethyl and the acetolactate synthase (ALS) inhibitor sulfosulfuron and (2) characterize the resistance mechanisms. Results: Bromus tectorum populations were confirmed to be resistant to the ACCase-inhibiting herbicides tested. The levels of resistance varied among the populations for clethodim (resistance ratio, RR = 5.1–14.5), sethoxydim (RR = 18.7–44.7), fluazifop-P-butyl (RR = 3.1–40.3), and quizalofop-P-ethyl (RR = 14.5–36). Molecular investigations revealed that the mutations Ile2041Thr and Gly2096Ala were the molecular basis of resistance to the ACCase-inhibiting herbicides. The Gly2096Ala mutation resulted in cross-resistance to the aryloxyphenoxypropionate (APP) herbicides fluazifop-P-butyl and quizalofop-P-ethyl, and the cyclohexanedione (CHD) herbicides clethodim, and sethoxydim, whereas Ile2041Thr mutation resulted in resistance only to the two APP herbicides. All B. tectorum populations were susceptible to sulfosulfuron (RR = 0.3–1.7). Conclusions: This is the first report of target-site mutations conferring resistance to ACCase-inhibiting herbicides in B. tectorum. The results of this study suggest multiple evolutionary origins of resistance and contribute to understanding the patterns of cross-resistance to ACCase inhibitors associated with different mutations in B. tectorum.

Original languageEnglish (US)
Pages (from-to)4025-4033
Number of pages9
JournalPest Management Science
Issue number10
StatePublished - Oct 2023

All Science Journal Classification (ASJC) codes

  • Agronomy and Crop Science
  • Insect Science

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