Cyhalofop-butyl and Glyphosate Multiple-Herbicide Resistance Evolved in an Population Collected in Chinese Direct-Seeding Rice.

is a typical xerophytic weed species with a cosmopolitan distribution. It is invasive and highly adaptable to diverse habitats and crops. Due to rice cropping-pattern changes, has become one of the main dominant grass weeds infecting direct-seeding paddy fields. A Chinese population has evolved multiple-herbicide resistance to cyhalofop-butyl and glyphosate. In this study, the multiple-resistance profile of to these two different types of herbicides and their resistance mechanisms were investigated. Whole-plant dose-response assays indicated that the multiple-herbicide-resistant (MHR) population exhibited 10.8-fold resistance to cyhalofop-butyl and 3.1-fold resistance to glyphosate compared with the susceptible (S) population. ACCase sequencing revealed that the Asp-2078-Gly mutation was strongly associated with resistance to cyhalofop-butyl. The MHR plants accumulated less shikimic acid than S plants at 4, 6, and 8 days after glyphosate treatment. In addition, no amino acid substitution in the gene was found in MHR plants. Further analysis revealed that the relative expression level of in MHR plants was 6-10-fold higher than that in S plants following glyphosate treatment, indicating that overexpression may contribute to the glyphosate resistance. Furthermore, the effectiveness of nine post-emergence herbicides against were evaluated, and one PPO inhibitor pyraclonil was identified as highly effective in controlling the S and MHR populations.