Stacked mutations in multi‐copy AHAS genes enhance sulfonylurea herbicide resistance in soybean

SUMMARY Weeds are a major factor that negatively impact crop yields. Developing herbicide‐resistant germlines is crucial for efficient weed control. Sulfonylurea‐ and pyrimidinyl benzoate‐based herbicides inhibit the function of acetohydroxyacid synthase (AHAS), a key enzyme in the biosynthesis of branched‐chain amino acids in plants. To create soybean plants resistant to these classes of herbicides, we performed base editing of AHAS genes in Glycine max . A guide RNA was designed to target the codon for proline‐182 in GmAHAS2 , with the prediction that off‐target base editing might also occur in the GmAHAS3 and GmAHAS4 genes. We selected six genome‐edited soybean lines, each carrying distinct mutations in GmAHAS2 , GmAHAS3 , or GmAHAS4 . These lines were treated with three different AHAS‐targeting herbicides to evaluate resistance. The results show that the number of mutated GmAHAS genes and the mutation patterns significantly influence herbicide resistance.