|Koger Iii, Clifford|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 1/2/2004
Publication Date: 1/2/2004
Citation: Koger III, C.H., Henry, W.B., Shaner, D.L. 2004. Shikimate accumulation in conventional corn and soybean as affected by sub-lethal rates of glyphosate. Meeting Abstract. Presented at the SWSS Annual Meeting. Jan. 23-30, 2004. Memphis, TN. Interpretive Summary:
Technical Abstract: An assay was evaluated as a relatively inexpensive and fast procedure to measure shikimate accumulation in conventional corn and soybean following glyphosate application. This research was conducted at three locations during the summer of 2003: Stoneville, MS, Fort Collins, CO, and Akron, CO. Conventional corn and soybean in addition to roundup ready corn and soybean were all planted twice so that growth stage could also be evaluated with respect to shikimate accumulation/detection. Glyphosate, Roundup Weathermax, at the 1X rate, 1.6 L/ha, was applied to 9-10 lf corn and 6-7 lf soybean (planting date one) and to 6-7 lf corn and 2-3 lf soybean (planting date 2) at approximately 140 L/ha and 160 kPa. The other treatments included 1/4X, 1/16X, and 0X rates. Cork borers were used to sample young leaves from the plant at 1, 4, 7, 14, and 21 days after herbicide application. 12 leaf discs per leaf comprised a single sample which was then subjected to a series of extractions. The OD value at 380 was then read to determine shikimate level. Using this assay, shikimate was most readily detectable in soybean at 4-7 days after application and in corn at 7-14 days after application depending upon growth stage. Species did not influence shikimate accumulation dramatically. For a producer to use this assay to detect shikimate exposure on crops, he would have to gather samples immediately following the appearance of injury symptoms. Further refinement of this assay may eventually lead to an assay that could be conducted in the field.