Fenoxaprop-P-ethyl resistance conferred by cytochrome P450s and target site mutation in Alopecurus japonicus

BACKGROUNDAlopecurus japonicus is a serious grass weed species in wheat fields in eastern Asia, and has evolved strong resistance to acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Although target-site resistance (TSR) to ACCase inhibitors in A. japonicus has been reported, non-target site resistance (NTSR) has not. This study investigated both TSR and NTSR in a fenoxaprop-P-ethyl-resistant A. japonicus population (AHFD-3), which was collected in Feidong County, Anhui Province, China. RESULTSWe found that AHFD-3 exhibited high resistance to fenoxaprop-P-ethyl and low resistance to flucarbazone-sodium. The sensitivity of AHFD-3 to fenoxaprop-P-ethyl increased significantly after treatment with cytochrome P450 (P450) inhibitors; however, such synergies between P450 inhibitors and fenoxaprop-P-ethyl were not found in two control populations. Sequences of the entire carboxyltransferase domain of A. japonicus ACCase were obtained, and AHFD-3 plants showed an Asp-2078-Gly substitution in the ACCase. With the derived cleaved amplified polymorphic sequence (dCAPS) method, we found that 85.4% of the plants of AHFD-3 carried this mutation. The P450 content in AHFD-3 plants was significantly higher than those of the two control populations after treatment with fenoxaprop-P-ethyl. Ten partial sequences of P450 genes in A. japonicus were cloned. Three P450 genes were up-regulated 12h after fenoxaprop-P-ethyl treatment, which were all from the P450 subfamily CYP72A. Moreover, a P450 gene from the P450 family CYP81 was up-regulated after fenoxaprop-P-ethyl treatment in all populations studied. CONCLUSIONFenoxaprop-P-ethyl resistance in AHFD-3 plants was conferred by up-regulation of cytochrome P450s in the CYP72A subfamily and target site mutation of the ACCase gene. (c) 2018 Society of Chemical Industry