Mechanism of atrazine resistance in atrazine- and HPPD inhibitor-resistant Palmer amaranth (Amaranthus palmeri S. Watson) from Nebraska

Palmer amaranth (Amaranthus palmeri S. Watson) is the most problematic weed species in the US agriculture. A Palmer amaranth biotype multiple resistant to atrazine and 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibitors was reported in a seed corn production field in Nebraska, USA. Rapid detoxification mediated by cytochrome P450 monooxygenases and increased HPPD gene expression were reported as the mechanisms of mesotrione resistance in atrazine- and HPPD inhibitor-resistant Palmer amaranth biotype from Nebraska; however, the mechanism of atrazine resistance is unknown. The objectives of this study were to investigate any target- or nontarget-site based mechanisms conferring atrazine resistance in resistant Palmer amaranth from Nebraska, USA. 14C-atrazine absorption and translocation studies revealed that reduced atrazine absorption or translocation were not involved as one of the mechanisms of atrazine resistance. Instead, greater 14C-atrazine absorption and recovery in treated leaves were observed in resistant compared to susceptible Palmer amaranth. No known mutations including Ser264Gly substitution in the psbA gene causing target-site based atrazine resistance were observed. However, parent 14C-atrazine was metabolized rapidly in less than 4 h after treatment in resistant plants, conferring enhanced atrazine metabolism as the mechanism of resistance.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author