Overexpression of and ( and ), and were related to cyhalofop resistance in a barnyardgrass accession from Arkansas.

Barnyardgrass [ (L.) P. Beauv.] is the most difficult-to-control weed species of rice production systems worldwide. It has evolved resistance to different herbicide sites of action, including the acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Target-site mutations conferring resistance to ACCase-inhibiting herbicides are well documented; however, the role of the different genes in conferring resistance to cyhalofop-p-butyl (cyhalofop), an ACCase-inhibiting herbicide, remains poorly understood. This research assessed the contribution of gene amplification and expression of genes in a cyhalofop-resistant barnyardgrass accession. Additionally, the expression of (s) and cytochrome P450 monooxygenases (s) genes as possible contributors to resistance to cyhalofop were investigated. Results demonstrated that gene amplification does not contribute to cyhalofop resistance. However, and were found to be overexpressed in the cyhalofop-resistant barnyardgrass accession. At 24 h after cyhalofop treatment, an overexpression of 2.0- and 2.8-fold was detected in and , respectively. In addition, (a gene) was found to be 2.5-fold overexpressed compared to the susceptible accession in the same time period. These results suggest that , and are crucial genes in contributing cyhalofop resistance in this barnyardgrass accession.