Event DAS-40278-9 maize expresses the aryloxyalkanoate dioxygenase-1 enzyme, which was originally identified in the soil bacterium Sphingobium herbicidovorans. This enzyme degrades 2,4-dichlorophenoxyacetic acid (2,4-D) and aryloxyphenoxypropionate herbicides (e.g., haloxyfop, cyhalofop, quizalofop, etc.); therefore, plants that contain this enzyme are tolerant to these herbicides. We employed the substantial equivalence approach to investigate the compositional safety of event DAS-40278-9 maize. A total of 82 different compositional analyses were conducted to evaluate the equivalence of event DAS-40278-9 and conventional maize. Analyte levels within the transgenic entries were either within literature ranges for non-transgenic maize or statistically indistinguishable from the non-transgenic near-isogenic hybrid, thus indicating substantial equivalence between event DAS-40278-9 and its conventional counterpart. These results agree with dozens of published studies for other transgenic events where input traits were found to have a negligible effect on crop composition compared with traditional breeding methods.

The European Food Safety Authority (EFSA) oversees the safety assessment of genetically engineered (GE) crops in the European Union and has developed a study design and statistical approach for assessing the compositional equivalency between a GE crop and the corresponding non-GE crop on the basis of the results from a small number of concurrently grown reference lines. Confidence limits around the differences in mean analyte composition between the GE variety and the reference lines are compared with equivalence limits on the basis of the variability of the reference lines. Here, we evaluated the performance and consistency of the equivalence conclusions using a non-GE variety that is, by definition, equivalent to the non-GE crop. Using this approach across the same analytes with the same non-GE variety, it was found that equivalence could not be concluded for 19.7, 22.9, 25.4, and 53.5% of the analytes in four separate studies. In addition, equivalency conclusions for the same analyte often differed from study to study. These results call into question the consistency and value of this approach in the risk assessment of GE crops.

SummaryThe impact of crossing (‘stacking’) genetically modified (GM) events on maize‐grain biochemical composition was compared with the impact of generating nonGM hybrids. The compositional similarity of seven GM stacks containing event DAS‐Ø15Ø7‐1, and their matched nonGM near‐isogenic hybrids (iso‐hybrids) was compared with the compositional similarity of concurrently grown nonGM hybrids and these same iso‐hybrids. Scatter plots were used to visualize comparisons among hybrids and a coefficient of identity (per cent of variation explained by line of identity) was calculated to quantify the relationships within analyte profiles. The composition of GM breeding stacks was more similar to the composition of iso‐hybrids than was the composition of nonGM hybrids. NonGM breeding more strongly influenced crop composition than did transgenesis or stacking of GM events. These findings call into question the value of uniquely requiring composition studies for GM crops, especially for breeding stacks composed of GM events previously found to be compositionally normal.

The concentration of transgene products (proteins and double-stranded RNA) in genetically modified (GM) crop tissues is measured to support food, feed, and environmental risk assessments. Measurement of transgene product concentrations in breeding stacks of previously assessed and approved GM events is required by many regulatory authorities to evaluate unexpected transgene interactions that might affect expression. Research was conducted to determine how well concentrations of transgene products in single GM events predict levels in breeding stacks composed of these events. The concentrations of transgene products were compared between GM maize, soybean, and cotton breeding stacks (MON-87427 × MON-89034 × DAS-Ø15Ø7-1 × MON-87411 × DAS-59122-7 × DAS-40278-9 corn, DAS-81419-2 × DAS-44406-6 soybean, and DAS-21023-5 × DAS-24236-5 × SYN-IR102-7 × MON-88913-8 × DAS-81910-7 cotton) and their component single events (MON-87427, MON-89034, DAS-Ø15Ø7-1, MON-87411, DAS-59122-7, and DAS-40278-9 corn, DAS-81419-2, and DAS-44406-6 soybean, and DAS-21023-5, DAS-24236-5, SYN-IR102-7, MON-88913-8, and DAS-81910-7 cotton). Comparisons were made within a crop and transgene product across plant tissue types and were also made across transgene products in each breeding stack for grain/seed. Scatter plots were generated comparing expression in the stacks to their component events, and the percent of variability accounted for by the line of identity (y = x) was calculated (coefficient of identity, I). Results support transgene concentrations in single events predicting similar concentrations in breeding stacks containing the single events. Therefore, food, feed, and environmental risk assessments based on concentrations of transgene products in single GM events are generally applicable to breeding stacks composed of these events.

Research was conducted to determine picloram and aminopyralid sorption in five soils and three clay minerals and to determine if the potential for off-target movement of aminopyralid in soil is less than that of picloram. Nearly all sorption of picloram and aminopyralid occurred between 0 and 8 h, and the maximum theoretical sorption of picloram and aminopyralid were 10.3 and 15.2%, respectively. Freundlich distribution coefficients (Kf) for picloram ranged from 0.12 in a Cecil sandy loam to 0.81 in an Arredondo fine sand, whileKfvalues for aminopyralid ranged from 0.35 in a Cecil sandy loam to 0.96 in an Arredondo fine sand. Furthermore,Kfvalues of aminopyralid were higher than those of picloram in all soils tested.Kfvalues of picloram in clay minerals were 0.25 (kaolinite), 1.17 (bentonite), and 1,016.4 (montmorillonite), and those of aminopyralid were 5.63 (kaolinite), 2.29 (bentonite), and 608.90 (montmorillonite). It was concluded that soil sorption of aminopyralid was greater than that of picloram and that the potential for off-target movement of aminopyralid is less than that of picloram.