Resistance to acetyl-CoA carboxylase-inhibiting herbicides in Pseudosclerochloa kengiana and its molecular resistance mechanism

Whole-plant dose-response experiments were conducted to investigate the resistance levels of the putative resistant Pseudosclerochloa kengiana population to acetyl-CoA carboxylase(ACCase)- inhibiting herbicides. And ACCase gene fragments were amplified, sequenced and compared with the susceptible population, so as to identify its molecular resistance mechanism. The results of whole-plant dose-response assays showed that the putative resistant population SD-32 was resistant to fenoxaprop-pethyl (16.5-fold), clodinafop-propargyl (7.5-fold), sethoxydim (15.0-fold), clethodim (4.4-fold), and pinoxaden (5.7-fold) compared to the reference susceptible population SD-6. Partial chloroplastic ACCase sequences revealed that the resistant population SD-32 possessed an Asp-to-Gly substitution at the ACCase codon position 2078, which resulted from a nucleotide change from GAT to GGT. This study concluded that the change from Asp to Gly mutation at the amino acid position 2078 in the plastid ACCase was an important reason for the resistance to ACCase-inhibiting herbicides in P. kengiana.