Confirmation and characterisation of ALS inhibitor resistant Poa trivialis from Ireland.

Relying on one broad-spectrum product to control grass weeds has resulted in cases of resistance to acetolactate synthase (ALS) inhibitors in species that were not the primary target such as Poa trivialis (POATR), in wheat fields in Ireland. In this study, we have characterised ALS inhibitor resistance in two populations of POATR-R, suspected of being resistant, to (i) sulfonylurea (SUs)-mesosulfuron + iodosulfuron (the selecting agent), (ii) SU + sulfonylamino‑carbonyl-triazolinone (SCT)-mesosulfuron + propoxycarbazone, and (iii) triazolopyrimidine (TP)-pyroxsulam ALS chemistries. Resistant POATR-R populations showed ALS inhibitor cross-resistance associated with target-site resistance (TSR) mutations.