Involvement of glutamine synthetase 2 (GS2) amplification and overexpression in Amaranthus palmeri resistance to glufosinate.

Amplification and overexpression of the target site glutamine synthetase, specifically the plastid-located isoform, confers resistance to glufosinate in Amaranthus palmeri. This mechanism is novel among glufosinate-resistant weeds. Amaranthus palmeri has recently evolved resistance to glufosinate herbicide.

Functional PPO2 mutations: co-occurrence in one plant or the same ppo2 allele of herbicide-resistant Amaranthus palmeri in the US mid-south.

Background: Protoporphyrinogen IX oxidase 2 (PPO2) inhibitors are important for the management of glyphosate- and acetolactate synthase-resistant Palmer amaranth [Amaranthus palmeri (S.) Wats.].