RT Journal Article
SR Electronic
T1 Prediction of glyphosate resistance level based on <em>EPSPS</em> gene copy number in <em>Kochia scoparia</em>
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 047878
DO 10.1101/047878
A1 Todd A. Gaines
A1 Abigail L. Barker
A1 Eric L. Patterson
A1 Philip Westra
A1 Eric P. Westra
A1 Robert G. Wilson
A1 Andrew R. Kniss
YR 2016
UL http://biorxiv.org/content/early/2016/04/09/047878.abstract
AB Glyphosate-resistant (GR) Kochia scoparia has evolved in dryland chemical fallow systems throughout North America and the mechanism involves 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication. Sugarbeet fields in four states were surveyed for K. scoparia in 2013 and tested for glyphosate-resistance level and EPSPS gene copy number. Glyphosate resistance was confirmed in K. scoparia populations collected from sugarbeet fields in Colorado, Wyoming, and Nebraska. The GR samples all had increased EPSPS gene copy number, with median population values up to 11. An empirical model was developed to estimate the level of glyphosate-resistance in K. scoparia based on EPSPS gene copy number. The results suggested that glyphosate susceptibility can be accurately diagnosed using EPSPS gene copy number, and further increases in EPSPS gene copy number could increase resistance levels up to 8-fold relative to susceptible K. scoparia. These trends suggest that continued glyphosate selection pressure is selecting for higher EPSPS copy number and higher resistance levels in K. scoparia. By including multiple K. scoparia samples lacking EPSPS gene duplication, our empirical model provides a more realistic estimate of fold-resistance due to EPSPS gene copy number compared to methods that do not account for normal variation of herbicide response in susceptible biotypes.