Confirmation and detection of novel acetolactate synthase- and protoporphyrinogen oxidase–inhibiting herbicide-resistant redroot pigweed (<i>Amaranthus retroflexus</i>) populations in North Carolina

Abstract Complaints of control failures with acetolactate synthase (ALS)- and protoporphyrinogen oxidase (PPO)-inhibiting herbicides on redroot pigweed ( Amaranthus retroflexus L.) were reported in conventional soybean [ Glycine max (L.) Merr.] fields North Carolina. Greenhouse dose–response assays confirmed that the Camden County Pasquotank populations less sensitive to ALS- PPO-inhibiting compared susceptible A. populations, suggesting evolution resistance these herbicides. Sanger sequencing target genes determined population carried a Trp-574-Leu mutation ALS gene an Arg-98-Gly PPX2 gene, while His-197-Pro (first documentation genus), but no was detected gene. Single-nucleotide polymorphism (SNP) genotyping developed enable efficient screening future order limit spread herbicide-resistant populations. In addition, preliminary testing revealed three mutations ubiquitous respective These two represent first cases United States, as well this particular herbicide-resistance profile inhabiting America. While found population, we suggest has evolved herbicides, mechanism is be determined.