C. Hupfer et al., PCR-based quantification of genetically modified Bt maize: single-competitive versus dual-competitive approach, EUR FOOD RE, 212(1), 2000, pp. 95-99
Methods for the quantification of transgenic insect-resistant Bt maize by s
ingle- and dual-competitive PCR were developed. The analysis of mixtures of
DNA solutions, as well as of maize flours containing defined amounts of Bt
maize, demonstrated the usefulness of single-competitive PCR based on coam
plification of the CDPK promoter/cry1A(b) gene region of Bt maize and an in
ternal standard. Upon heat treatment of DNA solutions and maize flour, resp
ectively, the recovery of the Bt proportion compared to the starting materi
al determined by single-competitive PCR decreased significantly. This syste
matic error could be compensated for by using a dual-competitive approach b
ased on PCR quantification of the transgenic target sequence of Bt maize an
d of the maize specific invertase gene (ivr1).