Oct 16, 2002

Archive

Send

International biosafety

Bt-maize in Mexico: Questions remain

The incrossing of foreign genes from genetically modified plants to local native varieties and wild plants has become a key focus of safety research internationally. In centres of biodiversity, as Mexico is for maize, the release of genetically modified organisms is particularly problematic. Several papers presented at the International Biosafety Symposium in Beijing addressed this topic.

Have genes from Bt maize encroached into Mexican maize varieties? This issue has been hotly debated both by the scientific community and the general public since the publication of an article in the renowned scientific journal Nature in November 2001.

In the meantime the focus of debate has shifted. The question of whether Btgenes are actually present in local varieties is no longer in the spotlight, but rather the potential consequences of outcrosses on biodiversity.

A report produced by the Mexican government was quoted at the Beijing symposium. According to this report, Bt genes have already spread extensively amongst the indigenous maize varieties in at least one Mexican state, despite the fact that there is a moratorium on the cultivation of genetically modified maize plants in Mexico. It is assumed that the Bt genes originate from GM maize grown in the USA, the seeds of which have been used by Mexican farmers to cross with their own maize varieties. Since farmers in Mexico regularly exchange seed with one another, the Bt genes have rapidly spread.

Outcrossing – A threat to biodiversity?

The discussion triggered by these findings essentially revolves around two issues.

• What is the likelihood of foreign genes outcrossing to regional varieties and related wild plants?
• What effect does this have on genetic diversity - both on maize varieties used in Mexico, the regional system of seed production, breeding and maize cultivation, and also on related wild plants? Teosinte, the wild grass from which maize descended, is still found in Mexico, the homeland of maize.

So far, safety research has been unable to provide any reliable answers. Even the symposium in Beijing failed to clarify whether the incrossing of foreign genes in Mexico actually signifies a threat to the genetic diversity of maize varieties and wild plants.

The papers presented at the symposium dealt principally with methodical questions and collecting and evaluating data: what farming practice in Mexico looks like, the current level of genetic diversity of local varieties, the likelihood of incrossing in wild plants and whether the Bt gene, which can protect plants against certain pests, can alter the fitness of wild plants and therefore the composition of plant communities.

Future research projects will need to provide the necessary data to enable some of these questions to be answered in a better and more quantifiable way.