Abstract
The expression of the CP4 EPSPS protein in genetically engineered (GE) soybean confers tolerance to the Roundup® family of agricultural herbicides. This study evaluated the variability of CP4 EPSPS expression using an enzyme-linked immunosorbent assay in soybean tissues collected across diverse germplasm and 74 different environments in Argentina, Brazil and the USA. Evaluated material included single and combined (stacked) trait products with other GE traits in entries with cp4 epsps gene at one or two loci. The highest level of CP4 EPSPS was observed in leaf tissues, intermediate in forage and seed, and lowest in root tissues. Varieties with two loci had approximately twice the level of CP4 EPSPS expression compared to one locus entries. Variable and non-directional level of CP4 EPSPS was observed with other factors like genetic background, trait stacking, growing region or season. The maximum and average CP4 EPSPS expression levels in seed provided large margins of exposure (MOE of approximately 4000 and 11,000, respectively), mitigating concerns over exposure to this protein in food and feed from soybean varieties tolerant to Roundup® herbicides.
Highlights
Adoption of transgenic soybeanSince their introduction in 1996, genetically engineered (GE, referred to as GM or GMO) crops have delivered substantial agronomic, environmental, economic, health and social benefits to both farmers and society at large (ISAAA 2016)
The efficacy of the cp4 epsps gene that confers tolerance to glyphosate across commercial Roundup ReadyTM varieties has been uniform and consistent (Nair et al 2002)
The efficacy of the cp4 epsps gene for varieties used in this study was verified by treating the plots with RoundupÒ herbicide
Summary
Adoption of transgenic soybeanSince their introduction in 1996, genetically engineered (GE, referred to as GM or GMO) crops have delivered substantial agronomic, environmental, economic, health and social benefits to both farmers and society at large (ISAAA 2016). The 109-fold increase in acreage of GE crops during the 1996–2016 period of their commercialization is indicative of the benefits realized by both large and small farmers worldwide. In 2016, as much as 78% of soybean acres were planted with GE varieties resulting in the highest adoption rate of GE crops globally (ISAAA 2016). These varieties include products with both single and stacked GE traits. In 2016, herbicide-tolerant soybean was planted on 68 million ha, whereas varieties with stacked transgenes (herbicide-tolerance and insectprotected traits) were grown on 23.4 million ha worldwide (ISAAA 2016). As more GE traits become available to farmers, the proportion of varieties with stacked transgenes will become more prevalent
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