There can be no question that the commercial adoption of genetically modified (GM) crops represents an unprecedented economic success and bespeaks the value that growers place on these traits. In the Midwest USA and Canada, GM crops are represented byherbicide resistant corn (glyphosate and glufosinate), soybean (glyphosate), canola (glyphosate and glufosinate) and alfalfa (glyphosate), and insect resistant corn (Bt). GM corn may have multiple ('stacked') traits including glyphosate and glufosinateresistance and Bt (resistance to Lepidoptera and Coleoptera are in separate GM events). In 2006, glyphosate resistant canola cultivars were estimated to encompass 65% of the planted area while glufosinate represented 32%. Glyphosate resistant soybeans are planted on at least 89% of the U. S. soybean area, and the percentage is higher in many Midwestern states. This is a remarkable increase since the introduction of the GM soybean in 1996. Corn cultivars with glyphosate resistance were introduced in 1997and with glufosinate resistance in 1998 and are currently planted on 37-45% and 5%, respectively, of the hectares. Glyphosate-resistant alfalfa has been commercialized but is not planted on a significant area in the Midwest and has recently been returned to regulated status, because of concerns about gene escape.
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