Presence of transgenic proteins and their effect on the content of tannins and aflatoxins in commercial corn

Resumen

In Mexico, the state of Oaxaca was where contamination of native corn with genetically modified corn was first detected. However, few studies have focused on evaluating the effect of GM contamination on tannins (natural insecticides) and af latoxin contamination. In this work, transgenic pollutionwas monitored in thirteen corn genotypes (ten hybrids and three natives). The samples were collected in the states of Hidalgo (5), Morelos (2), State of Mexico (3) and Federal District (3). A gel assay and UV-vis light spectrophotometry were used to determine the presence and content of tannins; the enzyme immunoassay technique for the analysis of aflatoxins and the polymerase chain reaction (PCR) were used to identify the 35S promoter and the NOS terminator. 44% of the corn hybrids tested positive for transgenic sequences. Tannin content varied among the corn genotypes within a range of 1 300 to 3 060 mg L, expressed as tannic acid equivalents, and of 7.69 to 276.92 mg L expressed as catechol equivalents. There was a significant difference of the tannin content among corn hybrids depending on its origin. All corn hybrids presented aflatoxin contamination within a range of 1.2 to 12 ng g. It is concluded that in 50% of the corn hybrids contaminated with transgenic protein the content of gallotannins decreased (natural protection) and af latoxin contamination increased.