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Re: Hybridizing

  • Subject: Re: [IGSROBIN] Hybridizing
  • From: John MacGregor <jonivy@EARTHLINK.NET>
  • Date: Tue, 23 Oct 2001 19:20:11 -0700

Barry Roth wrote:

> Another approach is to artificially double the chromosome load of a diploid.
> This can be done by applying certain chemicals (colchicine is one) to seeds
> or to growing tip tissues (meristems) of the diploid variety.  I believe
> this has been done with P. x hortorum to bring certain characters into the
> tetraploid range (the "dark dwarf" condition is one).
>
> I experimented with this some years ago, without much success, although I
> had some fun in the process.  It seems that the dose of chemical necessary
> to cause doubling of chromosomes is very close to a lethal dose.  (No
> surprise -- it's really messing with the biochemical framework of the plant
> itself.)

> The chemicals are hazardous materials and must be handled with appropriate
> care.

Barry and all,

Colchicine does not JUST work on plant chromosomes.  There are cases on
record in which men who used colchicine in their experiments were rendered
sterile or sired children with serious birth defects.  It isn't something to
play around with.  One more confirmation of the old caution, "Don't mess
with Mother Nature!"

On the other hand, working with existing tetraploids, while difficult, is
not hopeless.  I have not hybridized with Pelargoniums, but evidence from
roses indicates that crosses between diploids and tetraploids are not all
dead ends.  Such crosses usually produce triploids, but some triploids
produce at least a few pollen grains that are either diploid or tetraploid
and are capable of mating with diploid or tetraploid eggs.  There are a few
examples of especially good cultivars that have at least one triploid
parent.  Statistically, this is rare, but it does happen.

John MacGregor
jonivy@earthlink.net





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