Validation of an enzyme immunoassay for monitoring Cry1Ab toxin in soils planted with Bt-maize (MON810) in a long-term field trial on four South German sites

For monitoring the environmental impacts of a genetically modified crop well-established methods are a key requirement for the collection of appropriate data. With regard to the fate of Cry1Ab protein from Bt-maize MON810 released by root exudates, plant residues and pollen deposition into soil, a highly specific and sensitive sandwich enzyme immunoassay for detection and quantification of Cry1Ab in soil matrix was developed. The assay was validated according to the criteria of EU-Decision 2002/657/EC for a range of soils originating from four selected experimental field sites in South Germany, where Bt-maize MON810 has been cultivated. On three sites Bt-maize was grown permanently for eight years whereas one site was cropped with Bt-maize for one year only. The validation of the method showed that the assay fulfils the validation criteria as prescribed in the guidelines of the EU-Decision with minor restrictions. When the assay was applied to field soil samples collected from the selected four experimental sites six months after harvest, no Cry1Ab protein was detectable. By ELISA-determination and quantification of Cry1Ab protein in soils collected from these sites at further time points more profound knowledge about the long-term behaviour of Cry1Ab protein in soil will be obtained.