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1 April 2007 Review of Glyphosate and Als-inhibiting Herbicide Crop Resistance and Resistant Weed Management
Jerry M. Green
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Weed management is a perennial challenge for growers, and continual innovation is essential to maintain the effectiveness of management technologies. The first generation of herbicide-resistant crops revolutionized weed control. However, weeds are adapting to crop systems that rely on a single mode of herbicide action. Crops with resistance to multiple modes of herbicide action could help maintain weed management. GAT/HRA is a new multiple herbicide–resistance technology for corn, soybean, and other crops. GAT/HRA combines metabolic glyphosate inactivation with an acetolactate synthase (ALS) enzyme that is insensitive to ALS-inhibiting herbicides. The mechanism to inactivate glyphosate is the glyphosate N-acetyltransferase enzyme, which transforms glyphosate into a nonphytotoxic metabolite. The gat gene is derived from a naturally occurring soil bacterium and optimized by repetitive gene shuffling and screening. The resistance mechanism to ALS-inhibiting herbicides is a double-mutant, highly resistant ALS (HRA) that is insensitive to all five classes of ALS herbicides. GAT/HRA crops will maintain natural tolerance to selective herbicides and thus provide more weed management options for growers to help deter weed spectrum shifts and delay the evolution of herbicide-resistant weeds.

Nomenclature: Glyphosate; corn, Zea mays L; soybean, Glycine max (L.) Merr.

Jerry M. Green "Review of Glyphosate and Als-inhibiting Herbicide Crop Resistance and Resistant Weed Management," Weed Technology 21(2), 547-558, (1 April 2007).
Received: 9 January 2006; Accepted: 1 November 2006; Published: 1 April 2007
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