Silviu-Alin Bacanu bacanus at
Tue Aug 7 23:06:43 EST 2001

"Daniel B. Wheeler" wrote:

> Totara <down at the.woods> wrote in message news:<3B676D7D.91909096 at the.woods>...
> > "Daniel B. Wheeler" wrote:
> >
> > > Totara <down at the.woods> wrote in message news:<3B65ABD5.1D07151D at the.woods>...
> > > > Daniel
> > > > Natural hybrids are cross pollinated by wind.
> > > > Manmade hybrids are cross pollinated in the nursery;
> > > > transgenic trees are modified using implantation of genes at the
> > > > microscopic DNA level.
> > >
> > > I guess I'm still confused. Natural hybrids would be something that
> > > happens in nature by wind pollination. Such _might_ occur in the
> > > creation of the Leland cypress, which is a cross between Alaska Yellow
> > > cedar and Monterey cypress. Might...but not very likely.
> > >
> > > Manmade hybrid are cross pollinated in the nursery. I think Leland
> > > actually chose trees in nature to cross-polinate by hand, but I could
> > > be wrong. But since it was still hybridized by man it's still a
> > > manmade hybrid, right?
> > >
> >
> > Leylands cross pollinated in a Welsh park where the parent trees grew together,
> > which they don't in nature, so in a way it is a man made natural hybrid.
> > Subsequent Leylands have been hand pollinated.
> >
> > >
> > > And a transgenetic tree would be something that was like a Leland
> > > cypress but with a gene for, say, an insecticide from a painted daisy
> > > (pyrethrium) inserted into the genetic make-up?
> >
> > Yes or worse, a sterility gene that renders all conifers sterile round and about.
> Wouldn't that require that genetic material be transferred? How could
> pine genes be transferred to cedar or vice versa? How could genetic
> material be transferred between fir and hemlock? Doesn't that go
> against the definition of "species"?

Not really. If the species are "close" genetically they can cross. You can
most of the time cross in the same genus and sometimes between different
genera inside the same family.
The more "distant" they are the less likely
they are to cross. Same general idea applies to grafting.
If you cross the more "distant" they are the less likely
 to have non-steryle offspring. At Pyrus repository in Corvallis(OR) website
they have a story about some clone that apears to be a cross between mountain ash
(Sorbus acuparia) of Genus Sorbus with Pyrus communis of genus Pyrus, both in
Rosaceae family. It is steryle as expected.

> > Or a pig gene that makes the tree look for its own truffles!
> Although I sense some facetiousness here, most trees in nature
> actually _do_ search for truffles. In fact, some truffles will not
> terminate unless the spores are affected by an exudate produced by
> tree roots. Pigs gene for the tree? Unlikely. But the problem I see is
> that somehow, an introduced gene could affect the tree's ability to
> survive over time.

Yes, that's the problem. The gene may give competitive advantage and
its frequency will baloon in the population because of its transmission
to uncommonly succesful offsprings. All the cereals (in US it may include corn)
have very close relatives among the rough volunteer weeds. You wouldn't want
to give them any more competitive advantage.
That is genetycal polution. By hybridizing you don't add new "succesful" genes to
the offspring, you just "pick and choose" the "best" available ones. That is
a lower level of polution. Either way they should cease this too
( where fruits are not wanted),
by obtaining triploid hybrids
(which have for gamets only ~(1/2)^10~1/1000 chance to
be viable; all the others have different number of alleles in different parts
of chromosomes and the resulting egg will almost certainly die).
For honey trees triploids increase the honey quantity because practically
the ovuls are never fertilized, so the nectar is produced until the ovul dies.

In France, last that I checked (4-5 years) they allowed only
transgenic corn because it cannot polute the native flora, due
to lack of "close relatives".

> > Could this be the end of the world as we know it?
> Who can tell over time? If no one asks the right questions, will
> anyone search for the answers? Technology is a wonderful thing. But
> it's only as good as the developers. And when developers have a vested
> interest...
> Daniel B. Wheeler

More information about the Ag-forst mailing list