Genome‐wide scan reveals CYP450 metabolism and stress response regulation underlying sulfosulfuron resistance in Bromus tectorum

Abstract BACKGROUND Cheatgrass ( Bromus tectorum L.) is a problematic weed species in the wheat cropping systems in the rainfed crop production areas of the inland Pacific Northwest (PNW) and now is becoming resistant to multiple modes of action. To identify mechanisms of non‐target site acetohydroxy‐acid/acetolactase synthase (AHAS/ALS) inhibitor resistance, 123 B. tectorum accessions were treated with three sulfosulfuron treatments (3.5, 35 and 350 g ha −1 ). A genome‐wide association study (GWAS) was performed using the results from the spray trials to unravel the mechanisms underlying sulfosulfuron resistance in B. tectorum . RESULTS A single nucleotide polymorphism (SNP) explained up to 48% of observed phenotypic variation of sulfosulfuron resistance in B. tectorum but was not located near the AHAS/ALS gene in the genome. Candidate genes included members of the cytochrome P450 (CYP450) 71 gene family, heat shock‐related proteins and a regulator of a heat shock‐related protein. Additionally, the analysis revealed hormonal regulators, and genes involved in abiotic stress response as candidate genes. CONCLUSION Non‐target site resistance for sulfosulfuron is present in B. tectorum populations of the inland PNW. A heat shock‐related protein 70 regulator and an auxin response factor gene was near the SNP that explained 48% of the variation in the GWAS, indicating auxin regulation and stress response pathways are involved in the resistance of B. tectorum populations to sulfosulfuron. The heat shock‐factor protein 70 regulated by the heat shock‐related protein 70 regulator was found on another significant SNP and the SNPs those two genes were on have a significant interaction. Additionally, the GWAS analysis indicated CYP450 genes are likely involved in resistance. © 2025 Society of Chemical Industry.