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.

1) There are a great many toxins present in plants including some plants
that are grown for food. No surprise there. Some writers go on to say that
it follows that "natural" doesn't necessarily mean safe. No surprise there
either. People have been poisoning themselves with plants for a long time
and the fad that anything called "natural" must be good is an invention of
the advertising world. Nobody knows what "natural" means in that context
anyway, probably nothing at all.

2) One such toxin is cucurbitacin which is found in squash and pumpkins.
There are cases reported of the amout of this toxin being increased through
selective breeding, some instances seem to have been deliberate in order to
create resistence to insects. I had trouble accessing original papers but
there is nothing improbable about that so I accept that it happened.

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. 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.

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

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.

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.
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.

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. The probability of harm from the
technique in general and the safety of each given organism both need to be
studied carefully until we get a handle on it. I don't want to see our
foods end up like some "wonder drugs" that have been pushed out by big
business only to be withdrawn years later when the effects were fully
evaluated. How will a dangerous GE gene be "withdrawn" some years down the
track once it becomes widespread?

David