Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/12/2010
Publication Date: 3/22/2010
Citation: Zobiole, L.H., Oliveira, R.S., Viesentainer, J.V., Kremer, R.J., Bellaloui, N., Yamada, T. 2010. Glyphosate affects seed composition in glyphosate-resistant soybean. Journal of Agricultural and Food Chemistry. 58:4517-4522. Interpretive Summary: The widespread use of the herbicide glyphosate and glyphosate-resistant (GR) crops represents a major advancement in effective weed management in conventional agricultural systems. Although glyphosate is applied to kill weeds infesting the crop, it also contacts and is absorbed by the soybean plant. The glyphosate molecule is systemic, meaning that it is moved throughout the living plant. Several reports suggests that as glyphosate is transported within the GR soybean plant, it may interact with a number of metabolic processes that might lead to adverse effects on plant seed composition. Based on these previous studies, we investigated the effect of glyphosate on mineral nutrient and fatty acid contents of seeds of soybean growing under greenhouse conditions. We found that many essential nutrients were consistently lower for GR soybean treated with glyphosate compared with GR soybean without glyphosate and the soybean parental lines that were not genetically modified to be GR. Also, contents of omega-3 and omega-6 fatty acids, comprising the main group of polyunsaturated fatty acids in seeds, were reduced in GR soybean receiving glyphosate treatment. Omega-3 and omega-6 fatty acids as part of human diets are important in maintaining healthy heart and brain functions. Although future field trials are required to determine if glyphosate affects nutrient and unsaturated fatty acid contents in seeds under variable environmental conditions, these preliminary results help partially explain some of the non-target effects of glyphosate that have been observed in current soybean production fields. The results are useful to other researchers, extension personnel, nutritionists, and farmers by providing an understanding of potential non-target effects of glyphosate in the development of the whole soybean plant. Further studies are needed to understand the mechanisms of glyphosate effects on seed composition and mineral nutrition. Understanding the implications of glyphosate on seed development would help in establishing programs for improving seed fatty acid composition and mineral nutrition qualities.
Technical Abstract: The cultivation of glyphosate-resistant (GR) soybeans has continuously increased worldwide in recent years mainly due to the importance of glyphosate in current weed management systems. However, not much has been done to understand eventual effects of glyphosate on GR soybean physiology, especially those related to seed composition with potential effects on human health. A first evaluation of glyphosate interference on GR soybeans compared with their near-isogenic non-GR parental lines, revealed a significant decrease in shoot tissue concentrations of macro and micronutrients, as well in photosynthetic parameters and biomass production. A second experiment conducted during a different crop season showed similar decreases imposed by glyphosate on these parameters and also alterations in soybean seed polyunsaturated fatty acids and seed mineral concentrations. The combined effects of decreased photosynthetic parameters and low nutrient availability in glyphosate-treated plants may contribute to possible undesirable properties of glyphosate affecting GR soybean seed composition.