A Brassica plant that comprises a first genome that encodes a herbicide-tolerant acetohydroxyacid synthase large subunit (AHASL) polypeptide and a second genome that encodes a second herbicide-tolerant AHASL polypeptide having an asparginine substitution at a position corresponding to position 653 of SEQ ID NO: 1 or position 638 of SEQ ID NO: 2. The two AHASL polypeptides provide resistance to an AHAS-inhibiting herbicide. The plant can be Brassica juncea and the herbicide can be imidazolinones, sulfonylureas, triazolopyrimidines or pyrimidinyloxybenzoates.