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Will transgenic plants cross
with wild relatives and cause environmental damage?

It should be remembered that plants will only cross with the same
species or very closely related species so that there must be a wild plant
closely related to the crop plant with which the crop plant can breed. The
concept that the gene in the closely related wild species can subsequently
be transferred to a range of other wild species, as has sometimes been
implied, will not occur. As in most cases with transgenic plants, each
case must be treated separately considering the crop in question and the
wild relative that could be a recipient of the gene that has been

In Canada, the crop of most concern for breeding with a wild relative
is canola (oilseed rape in Europe). Canola is a strange plant in that it
contains two genomes, one from the cabbage family and one from the mustard
family. The cabbage family genome poses no problems because of the absence
of wild relatives and if the gene is inserted in this genome it will not
be transferred. However, the presence of the mustard genome might allow
the plant to cross with wild mustard, in the process the cabbage genome is
lost. This cross has been shown in the laboratory and may occur naturally
in the field. Other crops in which outcrossing could be a possibility are
oats and alfalfa. The rest of the major crops grown in Canada should not
be a problem because of the absence of wild relatives. An analysis of
possible wild relatives to crop plants is specific for each region of the
world and a crop that has no wild relatives in Canada may have such
relatives in a tropical climate, for example.

The transfer of a gene from canola to wild mustard growing at the edge
of a canola field was measured in experiments described in Nature in 1998.
It showed that, although gene transfer can occur, the frequency is low and
the authors conclude that there is little risk of transfer of canola genes
to wild populations.

It is proposed that the presence of a transgene in a wild variety could
cause the development of a super weed. However, crop plants are not
usually effective competitors in a natural environment and hybrids would
also probably not be effective. This is being tested in canola. In
addition, the pernicious weedy nature of a plant is not a single genetic
trait but a complex series of attributes requiring multiple genes. The
concept that a single gene could confer these properties is unlikely.
Again, it is important to look at the gene involved and attempt to predict
its impact on a possible weed plant.

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