Isolation distance for genetically modified plants

Isolation distances are used in regions where genetically modified (GM) and conventional or organic crops are grown in co-existence. When different cropping systems are grown in proximity to each other, the "isolation distance" between fields refers to the area separating them, on which genetically modified pollen can settle without fertilising non-GM crops.

Goal of isolation distances

The goal of isolation distances is to minimise out-crossing of GM plants. If large amounts of GM pollen fertilise crops in a non-GM field, that harvest may no longer be declared "GM-free", and will require appropriate labelling if its GM content exceeds a certain limit (e.g. 0.9 percent in the European Union).

Design of isolation distances

Isolation distances are mostly empty spaces. They may be roads, uncultivated fields, or anything that separates two fields without actively hindering the drift of pollen. Separation methods between GM and non-GM fields which actively catch pollen are called "pollen barriers" or "buffer zones".

Factors influencing isolation distances

Many factors influence the width required for isolation. A major criterion is the crop species, since isolation distances often must be calculated according to pollen weight. Other influential criteria include the size and shape of fields, GM-contamination tolerance levels and, especially, local wind direction and weather conditions.

Isolation distances for maize

Maize is probably the best-studied crop in terms of isolation distances. Yet, recommendations for isolation distances have varied significantly. Under average conditions, the isolation distance may be 25 metres. However, in regions with small non-GM fields (< 1 hectare), or with crops being grown primarily for seed production, the isolation distance may be more than 100 metres.

Research on isolation distances

Among dozens of individual research projects, there are two extensive programmes investigating isolation distances for relevant crop species: SIGMEA and Co-Extra. Further results from various projects have been compiled by GMO-Safety.eu.

External links

* [http://sigmea.dyndns.org SIGMEA - European research programme on the biological safety of GM plants]
* [http://www.coextra.eu Co-Extra - European research programme on co-existence of GM and non-GM crops]
* [http://www.gmo-safety.eu GMO-Safety - Compilation of research on the biological safety of GM organisms]