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United States Department of Agriculture

Agricultural Research Service

Research Project: WEED BIOLOGY AND ECOLOGY, AND DEVELOPMENT OF SUSTAINABLE INTEGRATED WEED MANAGEMENT SYSTEMS FOR COTTON, SOYBEAN, CORN

Location: Crop Production Systems Research Unit

Title: Glyphosate Effect on Shikimate, Nitrate Reductase Activity, Yield, and Seed Composition in Corn

Authors
item Reddy, Krishna
item Bellaloui, Nacer
item Zablotowicz, Robert

Submitted to: Journal of Agriculture and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2010
Publication Date: March 17, 2010
Citation: Reddy, K.N., Bellaloui, N., Zablotowicz, R.M. 2010. Glyphosate Effect on Shikimate, Nitrate Reductase Activity, Yield, and Seed Composition in Corn. Journal of Agriculture and Food Chemistry. 58:3646-3650.

Interpretive Summary: Glyphosate application frequency has increased with the adoption of glyphosate-resistant (GR) crops, and glyphosate drift complaints from ground or aerial applications are common in the Mississippi Delta. The effect of glyphosate on nitrogen assimilation, nitrate reductase activity and seed composition in non-GR and GR corn is unknown. Scientists at Crop Production Systems Research Unit and Crop Genetics Research Unit, Stoneville, Mississippi, have conducted a 2-yr field study to determine (1) the effects of glyphosate drift on visual injury, shikimate accumulation, nitrate reductase activity, leaf nitrogen, yield, and seed composition in non-GR corn, and (2) the effects of glyphosate at label rates on nitrate reductase activity and seed composition in both GR and GR stacked with glufosinate-resistant trait corn. Glyphosate caused injury and increased shikimate levels in non-GR compared to nontreated corn. In non-GR corn, glyphosate drift did not affect starch content, but increased seed protein while reducing leaf nitrogen reductase activity, leaf nitrogen, grain yield, and seed oil. In GR and GR stacked with glufosinate-resistant corn, glyphosate applied at label rates did not affect corn yield, leaf and seed nitrogen, or seed composition (protein, oil, and starch content). These results demonstrate that the potential for severe yield loss in non-GR corn exposed to glyphosate spray drift.

Technical Abstract: A 2-yr field study investigated the effects of glyphosate drift rate on plant injury, shikimate accumulation, nitrate reductase activity, leaf nitrogen, yield, and seed composition in non-glyphosate-resistant (non-GR) corn (Zea mays L.) and the effects of glyphosate at label rates on nitrate reductase activity and seed composition in glyphosate-resistant (GR) and GR stacked with glufosinate-resistant trait corn. Glyphosate at 105 g ae/ha was applied once at 3 or 6 weeks after planting (WAP) to non-GR corn. Glyphosate at 840 or 1260 g ae/ha was applied twice at 3 and 6 WAP to transgenic corn. Glyphosate caused injury (45-55%) and increased shikimate levels (24-86%) in non-GR compared to nontreated corn. In non-GR corn, glyphosate drift did not affect starch content, but increased seed protein 8-21% while reducing leaf nitrogen reductase activity 46-64%, leaf nitrogen 7-16%, grain yield 49-54% and seed oil 18-23%. In GR and GR stacked with glufosinate-resistant corn, glyphosate applied at label rates did not affect corn yield, leaf and seed nitrogen, or seed composition (protein, oil, and starch content). Yet, nitrate reductase activity was reduced 5-19% with glyphosate at 840 + 840 g/ha rate and 8-42% with glyphosate at 1260 + 1260 g/ha rate in both GR and stacked corn. These results demonstrate the potential for severe yield loss in non-GR corn exposed to glyphosate.

Last Modified: 9/21/2014
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