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HIST: SPEC: Paltec (pallida crosses)

From: Sharon McAllister <73372.1745@compuserve.com>

Message text written by Jan Clark:

If Sharon is out there, I would like some advice re genetics. It may be
I have oversimplified things, but I think it is true that most species 
plants are genetically homozygous. That is, their genes take the form of
BB, CC etc.

Sorry, but you really have oversimplified things a bit.  I believe that you
are thinking about karyotypes and have inadvertently extended the
uniformity of chromosome type to the level of individual genes.  Although
karyotypes are consistent, a species is certainly not homozygous for all

>  If this is so, I would expect all crosses between the same 2 parents of
pallida and I. tectorum to have almost exactly the same genetic make up,
be for the most part, identical. Am I correct?
This is the basis for producing F1 seedlings from stock plants of pansies, 
etc, and producing F1 chickens from pure bred stock.

You can expect phenotypes to be much more similar than genotypes, and the
relative uniformity that is typical of F1 seedlings is attributable
primarily to the dominant/recessive or blending interaction of the traits
that are characteristic of each ancestral line.  This shows up in the F2
generation in the form of greater diversity.  

Yes, it is certainly possible to get exceptionally uniform F1 seedlings, as
is customary in seed crops.  This is done by breeding parental stocks to be
as close to completely homozygous as possible, then crossing them to
produce the desired F1.  The usual technique for producing the parental
lines is to self and rogue for successive generations -- but the catch is
that this does not work for many iris species.  When working with iris,
unless you have line-bred a species toward homozygousity it is best to
assume each clone is heterozygous for those traits that are variable within
the species.  

Sharon McAllister

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