Resistance to ACCase-inhibiting herbicides in an Asia minor bluegrass (Polypogon fugax) population in China.

Asia minor bluegrass (Polypogon fugax) is a common annual grass weed of winter crops distributed across China. We conducted a study on the resistance level and the mechanism of resistance to ACCase-inhibiting herbicides in a P. fugax population from China. Whole-plant dose-response experiments in greenhouse showed that the resistant P. fugax population was 1991, 364, 269, 157, and 8-fold resistant to clodinafop-propargyl, fluazifop-p-butyl, haloxyfop-R-methyl, quizalofop-p-ethyl and fenoxaprop-p-ethyl relative to the reference susceptible population, which was susceptible to all the five AOPP herbicides. Much lower R/S values of 3.5, 2.4 and 3.5, respectively, were detected for clethodim, sethoxydim and pinoxaden. Molecular analysis of resistance confirmed that the Ile2041 to Asn mutation in the resistant population conferred resistance to AOPP herbicides, but not to CHD and DEN herbicides. This is the first report of a target site mutation that corresponded to resistance to AOPP herbicides in P. fugax. Proper resistance management practices are necessary to prevent ACCase-inhibiting herbicides from becoming ineffective over wide areas.