Tr-res canola, tinkered, diddled...

Tue Jun 29 10:05:53 EST 1993

    The discussion re herbicide resistant transgenics has IMHO been
reasonable and the transfer of herbicide or insect resistance to
weedy relatives is a real issue and one I address in classes.
    The triazine resistance referred to by Conrad Black (this is a
very well-known name in Canadian financial circles) from New Zealand
is the result of a mutation in a chloroplast gene which prevents
binding of the herbicide to a protein involved in electron transport
in photosystem II. This same single base mutation has been observed
in a number of weed species around the world in cropping systems
where atrazine (and relatives) was applied continually for several
years, thereby putting weed populations under considerable selection
pressure. In Canada a weed biotype of Brassica campestris (wild
mustard) was discovered in a corn field where atrazine had been used
for several years (Phytoprotection, 1978, 59:117) and subsequent
genetic analysis showed that it was cytoplasmically-inherited
It was relatively easy to backcross the two
canola species, B. campestris and B. napus into this cytoplasm and
recover a highly resistant crop plant (Can J Genet Cytol, 1980,
22:167). The problem with this cytoplasm (and presumably the
mutation) was that yield was lower and so was oil content, which
demonstrates how difficult it is to genetically "improve" some traits
in plants. As a result triazine resistant canola is not used to any
extent (to my knowledge) in Canada or elsewhere.
    Regarding the references provided by Joe Cummins to support his
claims, rather than wasting more of our time on this stuff perhaps we
should send some of Joe Cummins extrapolations to some of the authors
of these papers for comment (with apologies, of course).

Larry R. Erickson,
Department of Crop Science,
University of Guelph,
Guelph, Ontario,
Canada  N1G 2W1
Fax: 519-763-8933  Phone: 519-824-4120 Ext. 3398

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