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Re: hybridizing question


Chick, Clyde, Ran et al. ---
Let me jump in with a geneticist's point of view.  I say this admitting
that I have yet to see the results of a hosta cross through my hands.  But
hostas are plants, and I do know a little about how plants work.

Please excuse the quotations.  I think these are needed in this case:
[Clyde said]
> > If S&S is the pod parent, you are most likely to get something that
looks like
> > S&S.
[Chick replied]
> Which brings up the question, Why?  It has also been my experience that
seedlings
> resemble the pod more than the pollen parent.  If I remember my high
school
> biology, shouldn't each parent have an equal chance to have it's
characteristics
> predominate, depending on which genes are dominant or recessive?

Chick, you are correct about the "equal chance" if the only phenomena you
are observing are controlled by nuclear genes.  Remember, this is a hosta:
there are also plastid genes floating around to be considered.  And cell
layers, since the variegated hostas we love are chimerae.  

Characteristics controlled by plastid genes will follow the seed (pod)
parent.  Those controlled by nuclear genes will follow the Mendelian equal
chance (he called it "independent assortment") concept.  

If Gregor Mendel had worked with hosta, he would have never "discovered"
genetics!  

A second thing to consider is that it is very easy to contaminate a
cross-pollination with self-pollen, either by emasculating late, or by not
protecting the exposed stigma after cross-pollination.  Contamination can
really confuse the proportions you see in the seedlings.  To a geneticist
trying to determine inheritance patterns, this is a big problem.  To a
breeder looking for that needle in the haystack, it is not: you simply grow
out more seedlings.  

Finally, if the characteristics you are observing are dominant (or mostly
dominant), then the seedlings should be expected to show those dominant
characters, right?  If S&S contains a group of dominant characteristics,
then you should expect its progeny to show those.  

The gold color in S&S, for instance, may be caused by the August Moon
lethal, which is not a plastid-based color, but is a dominant nuclear gene
which is lethal when homozygous.  If this is true, then 2/3 of the S&S
progeny (from crosses to greens) should be gold, and 1/3 green.  This is
not the normal genetic pattern (1:2:1) because 1/3 of the embryos abort in
the seed or as very young seedlings (that's the effect of the lethal gene).
 This was determined first by Kevin Vaughn and published in an early AHS
Journal (back in the mimeograph days --- maybe #11 or #13).  

Rick G
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