Glyphosate effect on shikimate, nitrate reductase activity, yield, and seed composition in corn

Journal or Publishing Institution: Journal of Agricultural and Food Chemistry

Study: http://www.ncbi.nlm.nih.gov/pubmed/20180575

Author(s): Reddy, K.N., Bellaloui, N. and Zablotowicz, R.M.

Article Type: Peer Reviewed Study

Record ID: 2043

Abstract: When glyphosate is applied to glyphosate-resistant (GR) crops, drift to nonglyphosate-resistant (non-GR) crops may cause significant injury and reduce yields. Tools are needed to quantify injury and predict crop losses. In this study, glyphosate drift was simulated by direct application at 12.5% of the recommended label rate to non-GR corn (Zea mays L.) at 3 or 6 weeks after planting (WAP) during two field seasons in the Mississippi delta region of the southeastern USA. Visual plant injury, shikimate accumulation, nitrate reductase activity, leaf nitrogen, yield, and seed composition were evaluated. Effects were also evaluated in GR corn and GR corn with stacked glufosinate-resistant gene at the recommended label rate at 3 and 6 WAP. Glyphosate at 105 g ae/ha was applied once at 3 or 6 weeks after planting to non-GR corn. Glyphosate at 840 (lower label limit) or 1260 (upper label limit) 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 GR stacked corn. These results demonstrate the potential for severe yield loss in non-GR corn exposed to glyphosate drift.

Keywords: Corn, drift injury, glyphosate, seed nitrogen, shikimate, transgenic corn, chemical constituents of plants, field experimentation, grain yield, shikimic acid, yield components, leaves, corn oil, enzyme activity, nitrogen content, plant-incorporated protectants, transgenic plants, application rate, food composition, plant damage, lipid content, seasonal variation, genetic resistance, protein content, adverse effects, spray drift, delta soils, herbicide resistance, plants, Zea mays, crop losses, crop yield, enzyme activity, genetic engineering, genetic transformation, genetically engineered organisms, glyphosate, maize, nitrate reductase, seed oils, seeds, starch, transgenic plants, corn, genetic manipulation, genetically engineered plants, genetically modified organisms, genetically modified plants, GEOs, GMOs, transgenic organisms, United States of America, Mississippi, USA

Citation: Reddy, K.N., Bellaloui, N. and Zablotowicz, R.M., 2010. Glyphosate effect on shikimate, nitrate reductase activity, yield, and seed composition in corn. Journal of Agricultural and Food Chemistry, 58(6), pp.3646-3650.