MEMORANDUM SUBMITTED BY DR PHILIP J DALE,
JOHN INNES RESEARCH CENTRE (R27)
There are various stages in crop production,
storage and handling during which GM and non-GM plant material
can become mixed. The potential causes and the factors influencing
the extent of mixing are summarised below.
1. SEED SUPPLIED
TO FARMERS
Farmers often sow Certified Seeds that have
been produced using Statutory procedures to ensure high genetic
purity. These measures include cleaning the machinery used to
sow and harvest the crop, and the physical separation of similar
crops to minimise pollination between crops. The usual genetic
purity of Certified Seed is over 99.7 per cent.
Seeds produced by farmers from their previous
crop ("farmer saved seed") would generally not follow
such strict procedures and are likely to be less genetically pure.
2. CROPS GROWN
BY FARMERS
FOR FOOD
The potential sources of GM and non-GM crop
mixing are as follows:
— Certified seed used to establish
the crop, could be up to 0.3 per cent impure;
— Crop mixing with GM volunteer plants
that are already present in the soil when the crop is sown;
— Mixing with GM seeds present in sowing,
harvesting and storage equipment;
— Cross pollination with adjacent GM
crops. This will vary with the distance and sexual compatibility
between the GM and non-GM crop, and the method of pollen transport
(e.g. insects, wind).
3. COMMODITY
CROP PRODUCTION
Commodity crops are grown and handled on a substantial
scale, especially in North America. The biotechnology companies
release GM breeding lines under licence to plant breeding companies,
who develop GM crop varieties from them. Seeds of these GM varieties
are sold to farmers, and the biotechnology company sometimes collects
a technology transfer fee as part of the cost of the seed. The
GM crop is often produced, marketed and transported, along with
non-GM crops. Because of the nature of commodity crop production,
there is no easy mechanism for a biotechnology company to orchestrate
crop separation and seed segregation between GM and non-GM crops.
Effective segregation is probably only possible by regional separation
of GM and non-GM crops.
4. ORGANIC AND
GM CROPS PRODUCTION
The following considerations are important (see
Moyes & Dale 1999; www.gmissues.org).
— GM crops are approved following a
rigorous regulatory assessment;
— The two methods of GM and organic
crop mixing, are by seeds and pollination;
— There is extensive experience of
the production of high genetic purity seeds (as described above)
that can be used in the production of high genetic purity organic
crops;
— Some seeds used for organic agriculture
(especially maize) are imported from North America, where there
are large areas of GM maize production. It is possible that some
of the imported seed already has GM seed mixed with it;
— Organic agriculture has experience
of setting tolerance limits for spray and fertiliser drift fromnon-organic
agriculture;
— There is pollination and the movement
of pests and diseases between organic and non-organic crops.
5. METHODS TO
PREVENT OR
MINIMISE GENE
FLOW BY
POLLINATION
Various methods, in addition to physical separation,
are sometimes used or are being considered.
— Removal of flowers is sometimes practical
during the experimental phase of GM crop trials;
— The production of sexually sterile
plants and the use of vegetative reproduction;
— Chloroplast transformation to minimise
pollen transmission of the GM character;
— Terminator technology to produce
crops in which a hybrid between a GM and non-GM crop are non-viable.
This is currently not a workable system.
6. CONCLUSION
In practice it is virtually impossible to guarantee
complete genetic purity of any field grown crop. The only practical
solution is to accept tolerance limits of mixing between GM and
non-GM crop material.
The degree of mixing between GM and non-GM that
should be allowed depends on scientific and ideological arguments.
A useful baseline would be the 99.7 per cent purity defined in
the production of high purity Certified Seeds. There has been
extensive experience with crop management procedures to achieve
this level of purity.
30 November 1999
| 
