First Report on Resistance to ALS-Inhibiting Herbicides in the Broadleaved Weed Common Vetch (Vicia sativa L.) and Visual Detection of the Associated ALS Resistance Mutation

Common vetch (Vicia sativa L.), an economically significant crop, is also a detrimental weed in wheat fields in the middle and lower reaches of the Yangtze River, China. A population of V. sativa (AHLQ-1) exhibiting high resistance (>10-fold) to ALS inhibitors, tribenuron-methyl and florasulam, was identified. All resistant plants carried a Pro-197-Ser substitution in their ALS genes, rendering their ALS enzymes 16.89 times less sensitive. Molecular docking revealed that the binding energies between ALS active sites and tribenuron-methyl or florasulam were reduced by over 80% due to the mutation at codon position 197. A LAMP method was successfully developed to visually detect this mutation, and a dCAPS assay was established to distinguish specific resistance mutations between homozygotes and heterozygotes. Additionally, cytochrome P450 activity was significantly elevated in resistant plants, enhancing the herbicide metabolism and resistance. This is the first global report of ALS resistance naturally occurring in V. sativa. These findings will aid in breeding herbicide-resistant V. sativa and improve resistance management.