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RE: Tetraploids


I sure wish someone would work out the genetics of Hosta so we can stop all
this wrangling about what is possible and what is not. We seem to get into
this discussion every year.

First, Ben states that you can have tetraploid x tetraploid sterility, but
has anyone ever seen this in Hosta?  I assumed that tetraploids crossed
easily.  Also, the question of triploid blocks is interesting.  I ahve
always assumed that it was a contributer to serility in Hosta. Ben has
determined that Sum and Substance is a triploid (topic of discussion at the
National Convention), However it would be a rather fertile tetraploid.  I
would be curious what you opinion is.

Second, we have a set of criteria that we are using to determine a presumed
tetraploid sport in Hosta.  Remember we fail to have the genetic data to
back up our determinations.  {I notice Ben is still offering to test Hosta
for tetraploids using the only viable technique we presently have for this
species.  I may take you up on that, Ben.}  But in any rate, these are the
criteria that we use to determine a 'presumed tetraploid.'  Please note that
most of the plants in this category are probably chimeric polyploids, that
is diploid in one cell layer and polyploid in the other.  1)  The thickness
of the leaf increases and the leaf becomes more shiny.  This means that the
plant also has more substance.  2)  The plant grows more slowly and often to
a smaller size.  3) The plant is harder to TC especially when it come to
making roots.

A good example is Hosta Eagles Nest, a sport of Sum and Substance.  The two
cell layers differ from one another in growth and color.  Plants from the
center of the leaf are dark green, much thicker, more shiny than S & S, and
grow much more slowly.  Plants from the edge of the leaf are Sum and
Substance.  Clearly the center of the leaf of Eagles Nest has some kind of
genetic alteration, possibly it is to a polyploid.

Jim Anderson

-----Original Message-----
From: owner-hosta-open@mallorn.com
[mailto:owner-hosta-open@mallorn.com]On Behalf Of halinar@open.org
Sent: Thursday, June 28, 2001 12:03 PM
To: hosta-open@mallorn.com
Subject: RE: Tetraploids


>If you cross tetraploid  (4x) to diploid (2x) you get all
>triploids((4x -> 2x) + (2x -> 1x) = (3x).

That's assuming you don't have triploid block in hostas.  With
triploid block the triploid embryos that do get produced are aborted,
so when you cross a diploid with a tetraploid you don't get any seeds.
However, if the diploid is producing unreduced gametes, then that is
the same as a gamate from a tetraploid, so then all the seedlings from
a diploid crossed with a tetraploid will be tetraploid because the
diploid is behaving like a teraploid.

The problem with tetraploids in hostas that I can see is that I can't
easily see them!  With daylilies and also lilies you can look at the
plant and often, but not always, get an idea if it is a tetraploid.
In daylilies there is triploid block, but there is no triploid block
in lilies.  I thought at one time Ben said that hostas had triploid
block.  It would be easy enough to check if you have some hostas you
know are tetraploids.

Joe Halinar

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