Detection and characterization of resistance to acetolactate synthase inhibiting herbicides in Anisantha and Bromus species in the United Kingdom.

Anisantha and Bromus spp. are widespread and difficult to control, potentially due to the evolution of herbicide resistance. In this study, UK populations of four brome species have been tested for the early development of resistance to acetolactate synthase (ALS)-inhibiting herbicides commonly used in their control. Glasshouse assays confirmed reduced sensitivity to ALS-inhibiting herbicides in single populations of A. diandra, B. commutatus and B. secalinus, and in three populations of A. sterilis. By contrast, all 60 brome populations tested were sensitive to the ACCase-inhibiting herbicide propaquizafop and glyphosate. Dose-response with two ALS herbicides showed broad-ranging resistance in the A. diandra, A. sterilis and B. commutatus populations. In the B. commutatus population, this was associated with a point mutation in the ALS enzyme conferring target site resistance (TSR). Additionally, resistant populations of A. sterilis and B. commutatus populations contained enhanced amounts of an orthologue of the glutathione transferase phi (F) class 1 (GSTF1) protein, a functional biomarker of nontarget site resistance (NTSR) in Alopecurus myosuroides. There was further evidence of NTSR as these plants also demonstrated an enhanced capacity to detoxify herbicides. This study confirms the evolution of resistance to ALS inhibiting herbicides in brome species in the UK by mechanisms consistent with the evolution of both TSR and NTSR. These findings point to the need for increased vigilance in detecting and mitigating against the evolution of herbicide resistance in brome species in Northern Europe. © 2020 Society of Chemical Industry.