A mutant of the acetohydroxyacid synthase large subunit (AHASL) that has increased tolerance to a herbicide selected from imidazoliones, sulfonylureas, triazolopyrimidines and pyrimidinyloxybenzoates. The mutant is provided by three substitutions that can either be present in a single AHASL or split between two or three AHASLs. The substitutions are: a valine, threonine, glutamine, cysteine or methionine at position 122 of SEQ ID NO: 1 or position 90 of SEQ ID NO: 2 and alanine , glutamic acid, serine, phenylalanine, threonine, aspartic acid, cysteine or asparagine substitution at position 199 of SEQ ID NO: 1 or position 167 of SEQ ID NO:2 and a phenylalanine, asparagine, threonine, glycine, valine, isoleucine or tryptophan at position 653 of SEQ ID NO: 1 or position 621 of SEQ ID NO: 2.
