To the editor

Genetic flow between transgenic and native maize has apparently occurred in Mexico1, resulting in wild strains containing one or more transgenic sequences (most likely encoding Bt toxin). These “transgenic” native maizes not only have every single trait that has been selected and preserved for thousands of years (making them perfectly adapted to specific geographic regions), but now also possess an additional and desirable characteristic—insect resistance, a trait likely to be consciously preferred by Mexican peasant farmers. Diversity will not be affected. On the contrary, we can predict that this useful transgene will be found in increasing numbers and types of native maizes.

We believe it is important to stress this is not genetic contamination! Contamination means unexpected, undesirable, and uncontrollable spread; that is not happening. The spread will be induced because of the advantage of having a native corn with resistance to insects.

Maize is so dependent on human intervention that it cannot survive in the wild. Maize seeds are attached to a cob and cannot free themselves: it absolutely requires human intervention. As maize was first domesticated more than 6,000 years ago, only genes and alleles that are important for humans have been selected and preserved.

Still, if someone wants to remove the transgene from these plants, the procedure would be simple: select and multiply those susceptible maizes and do not harvest and multiply the insect-resistant ones. That is something no Mexican farmer will do.

Teosintes, ancestors and close relatives of corn, do not seem to be affected by genetic flow from (any) maize. Teosintes growing naturally in cornfields yield a very poor hybrid progeny. They do not release their seeds, and therefore the probability is very low for natural genetic introgression (incorporation of a gene or allele in a population) into teosintes. We also have found that teosintes are highly susceptible to insects and pathogens when growing under more intensive experimental field conditions, but they appear to be resistant to them when growing naturally in the wild.

Thus we conclude that even if the Bt transgene could be introgressed into teosintes, it will provide no biological advantage and thus would be lost by natural evolution. To reiterate2, there is no need for concern.