Molecular basis of resistance to mesosulfuron-methyl in Japanese foxtail, alopecurus japonicus

Abstract

Japanese foxtail (Alopecurus japonicus) has developed resistance to the acetolactate synthase (ALS) herbicide mesosulfuronmethyl, which has been used continuously for several years in winter wheat fields in eastern China. To ascertain the resistance degree of A. japonicus to mesosulfuron-methyl, whole-plant bioassays and in vitro inhibition assays were conducted. The results of the whole-plant bioassays showed that the resistance index of the resistant population, JS-5, to mesosulfuron-methyl was 100-fold higher than that of the susceptible population, JS-7, and the in vitro activity assays confirmed that the ALS sensitivity of the JS-5 to mesosulfuron-methyl was reduced. To further investigate the molecular basis of the resistance, the ALS genes of the JS-5 and JS-7 populations were cloned, sequenced, and compared. Gene sequence analysis revealed a proline-to-threonine substitution at amino acid position 197 of ALS in Domain A that potentially confers the resistance of A. japonicus to mesosulfuronmethyl in the JS-5 population. © Pesticide Science Society of Japan.