A nonnative Palmer amaranth (<i>Amaranthus palmeri</i>) population in the Republic of South Africa is resistant to herbicides with different sites of action

Abstract Palmer amaranth ( Amaranthus palmeri S. Watson) is not native to Africa. Based on the presence and persistence of A. populations, its invasive status in southern Africa classified as “naturalized.” Globally, one most troublesome weed species several crops, including soybean [ Glycine max (L.) Merr.], maize Zea mays L.), cotton Gossypium hirsutum L.). Certain populations various countries were reported be resistant herbicides with different sites action (SOAs). Two biotypes United States reportedly each have resistance representing five SOAs, between them a total eight SOAs are involved. Resistance mechanisms these involve target-site and/or non–target site resistance. Here we characterize specific population that was found Douglas district South showed herbicide SOAs. Initially, this discovered glyphosate-tolerant field, where it survived glyphosate treatment. Subsequently, greenhouse experiments conducted for potential additional molecular analyses reveal Results indicated chlorimuron-ethyl population, while &lt;90% control (decreased sensitivity) observed at label rate mesotrione, atrazine, saflufenacil, S -metolachlor. However, glufosinate, tembotrione, acifluorfen, dicamba, 2,4-D, metribuzin, acetochlor, isoxaflutole, diflufenican, pyroxasulfone effective controlling population. This profiling sensitivity has allowed development programs potentially minimize spread weed. In addition, analysis EPSPS revealed role higher copy number mechanism Ser-653-Asn mutation likely conferring acetolactate synthase–inhibitor chlorimuron-ethyl. No known mutations identified protoporphyrinogen oxidase–inhibitor group.