David Hare-Scott > writes
>
>Oz
>
>I have now had a chance to read the material that you pointed me towards.
>This is (in summary) what I have gathered from it.

>3) Also this article (that you quoted)
>http://www.geo-pie.cornell.edu/issues/convtoxins.html
>refers to the same kind of problem in potatos and celery (different toxins).
>Once again I accept that it happened. What I don't accept is the author's
>rather sweeping statement
>
>"Conventionally-bred crop varieties may actually pose a greater risk from
>increased plant toxins than genetically engineered plants."
>
>I cannot see anywhere that he/she substantiates such a comparison.
> There is
>NO attempt to evaluate the risks of either technique so I cannot see how
>anyone can say one is more risky than the other.

Actually that is incorrect. Significantly different varieties are
roughly checked but this would, for 'conventional', only be after
outcrossing with wild (or effectively wild) relations that may contain
(be known to contain) toxins. When crossing like this obviously the
first cross will contain 50% of the 'wild' species, which includes a lot
of unwanted genes most of which do unknown things. After multiple
crossing the breeder hopes to have selected the characteristics required
(pest resistance, colour, shape, whatever), but probably includes some
other 'wild' genes.

All (artificial) genetically modified crops in the west are checked in
feeding trials as far as this can be done. The one big advantage is they
know precisely the gene introduced and that they have introduced no
others. Which is, of course, why its such a valuable tool. It can take
decades to breed out the unwanted wild genes from a cultivar in the
conventional way.


>I take the point however
>that being new GM plants are subject to much higher scrutiny and testing
>than selectively bred varieties and that the presumption of safety of the
>latter is by no means guaranteed. If you know of any articles on line where
>the relative risks are evaluated I would be keen to see them.

They were about, but when this was a hot topic some years ago.

>What do I think of the relative risks? As I pointed out to start of the
>thred with Genetic Engineering (GE) and Selective Breeding (SB) are both
>Genetic Modification (GM). That does not say anything about their relative
>safety. GE involves direct transfer of genetic material including that from
>totally unrelated species. SB is the alteration of the frequency of
>selected genes in the target population by breeding from organisms showing
>favoured characteristic(s). In GE genes are directly modified, in SB
>existing genes are selected in favour of others, there is no alteration of
>the genes themselves.

Of course that's not quite right. In GE genes are not modified, they are
nicked (unmodified) from elsewhere and in SE we note many garden
varieties (eg cereals) are so packed with mutations and polyploidy that
they can no longer breed unaided with wild relatives.

>SB may select for a mutation but it does not create
>mutations.

Frankly an unknown selected mutation is quite a bit more hazardous than
a known artificially introduced gene. Is this splendidly pest resistant
variety a new mutation or a good selection? Ditto nice flavour? etc etc?

We actually don't know.

>SB is traditional Darwinian evolution being directed by humans by choosing
>the environment. By manipulating the environment we manipulate the gene
>frequencies in the population much faster than otherwise and in directions
>that would never be taken without human intervention. This is where nearly
>all our cultivated plant and domesticated animal varieties came from.

I don't think so. Most of the really useful characteristics are
mutations. Just consider the grossly deformed maize plant with teosinte.
Heck it doesn't have male and female bits of flower at the top but has
the female bits grotesquely poking out half way down.

>Is the SB process 100% free of risk? No way. But as we are only playing
>with the frequency of existing genes the scope for a bad result is limited.

Unfortunately not. Mutations happen. They get spotted.

>If it wasn't people would have be getting poisoned far to often since
>agriculture started and neither cultivated species nor the humans that
>depend on them would be what they are today. The huge growth of human
>population could never have happened if SB was very unsafe.

Its more that plant breeding is pretty safe. Unfortunately we don't
actually know if our plant species are safe because most have never been
tested. In fact feeding to animals is probably the only real test and
the species fed is very limited. Even so most feeds are restricted in
the amounts that should be fed due to animals showing negative
reactions. Often the precise reasons are not known but the safe feeding
amounts are.

Some have been known in farming for A VeryLongTime. Not putting tupping
ewes on a clovery/leguminous sward is one very nice example but there
are others.

>What about the risks of GE? To me it is an open question, one that we
>should put many resources into answering so we can determine the real risks.
>This needs to be done over a long period of time with plenty of redundant
>cross checking by different parties.

's OK. Massive worldwide experiment feeding to humans and livestock
worldwide now in its 15th year without problems.


--
Oz
This post is worth absolutely nothing and is probably fallacious.

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