|Nadler-Hassar, Talia - COLORADO STATE UNIVERSITY|
|Koger Iii, Clifford|
Submitted to: Weed Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2005
Publication Date: December 1, 2005
Citation: Shaner, D.L., Nadler-Hassar, T., Henry, W.B., Koger Iii, C.H. 2005. A rapid in vivo epsps assay with excised leaf discs. Weed Science. 53:769-774 Interpretive Summary: Glyphosate is one of the most widely used herbicides in the world and resistance to glyphosate is an increasing concern. Glyphosate resistance has been documented in 6 different weed species and there is a need to have a rapid method for screening weed populations for glyphosate resistance. An in vivo EPSPS assay was developed utilizing leaf discs. This assay can determine if a population is resistant to glyphosate within 24 hours and promises to be a good tool to screen weed populations for resistance to glyphosate so that farmers can change their weed management program, if needed.
Technical Abstract: An in vivo EPSPS assay using excised leaf tissue was developed to provide a fast and reliable method for identifying glyphosate resistant plants. The assay is based on glyphosate-induced accumulation of shikimate. There was a linear accumulation of shikimate in excised leaf discs of soybean and canola treated with 250 µM glyphosate for 48 h. The IC50 for the accumulation of shikimate in soybean and corn leaf discs was 33 and 88 µM, respectively. Leaf discs excised from glyphosate-resistant corn or soybean did not accumulate shikimate when treated with 500 µM glyphosate. Leaf discs taken from a number of field grown plants accumulated shikimate in a glyphosate dose-dependent manner. The accumulation of shikimate was dependent on light and the age of the leaf from which the disc was taken. The assay worked either in 96-well microtiter plates or in vials, and clearly differentiated between glyphosate resistant and susceptible crops. The assay was simple and robust and has the potential to be used as a high throughput assay to detect glyphosate resistance in weeds.