Cross-resistance pattern to ACCase-inhibiting herbicides in a rare Trp-2027-Ser mutation Chinese sprangletop (Leptochloa chinensis) population

ABSTRACT Chinese sprangletop (Leptochloa chinensis %#91;L.%#93; Nees) is an invasive and troublesome grass weed in the aerobic rice fields in China. The extensive and repeated use of acetyl-CoA carboxylase (ACCase)-inhibiting herbicides has resulted in herbicide resistance in this weed. The objectives of this study were to determine the resistance levels to ACCase-inhibiting herbicides of the putative resistant Chinese sprangletop population CM9-1, collected from a paddy field in Shanghai city, in comparison to the susceptible population SJ3-1, and to characterize its molecular resistance mechanism. The whole- plant dose-response experiments suggested that the population CM9-1 had high-level resistance to cyhalofop-butyl, metamifop and fenoxaprop-P-ethyl, with resistance index of 27.8, 21.4 and 26.2, respectively, and low-level resistance to sethoxydim and pinoxaden, with resistance index of 2.1 and 2.9, respectively, but was sensitive to clethodim. Sequence analysis of the CT domain of ACCase gene revealed a Trp-2027-Ser mutation in resistant plants of the CM9-1 population. This is the first report of the cross-resistance pattern of the Trp-2027-Ser mutation to ACCase-inhibiting herbicides in Chinese sprangletop.