Re: ploidy article & Blue Coloration question
>I read Joe Halinar's article at http://www.open.org/~halinar/poly.htm
>and he goes a long way toward helping to explain an approach of
>utilizing unreduced gametes as a means for ploidy conversion. This,
>however, was written about 10 years ago and I wonder where we are
Some people have some problems with understanding unreduced gametes
and how to use them, but once you find them it becomes easy to breed
tets using the diploids that produce the unreduced gametes. A diploid
normally produces haploid gametes, but some diploids produce diploid
gametes, which are called unreduced gametes. Well, tetraploids
normally produce diploid gametes, so an unreduced gamete from a
diploid united with a diploid gamete from a tet is the same as a tet x
tet cross. The secret is to find the diploid plants that produce
unreduced gametes and to have some known tets. Supposely, Ben claims
he has some 40 tetraploid hostas, but he doesn't tell us what they are
- maybe he doesn't have fourty!
The article you refer to was written for the daylily society in 1990.
It has taken about ten years for daylily people to wake up to the
value of unreduced gametes, but the big named hybridizers are still
doing the chemical conversion methods. My guess is that it will take
about ten years of effort before hosta hybridizers wake up to the
potential of unreduced gametes. When I first started working with
unreduced gametes in daylilies I got lucky and discovered some diploid
plants that were great at accepting tet pollen but wouldn't take any
diploid pollen. Since then many others have have found various
daylilies that produce either unreduced eggs or pollen. The process
is facilitated in daylilies by the presence of triploid block -
triploid seedlings rarely are produced. When you make a diploid x tet
daylily cross and get seeds you can almost be 100% certain the
resulting progenies are tetraploids because the triploids that you
would expect from a diploid x tet just do not survive. I don't know
if hostas have triploid block.
There is another factor you have to consider, and that is fertility
and incompatibility problems. A diploid producing unreduced eggs
might not produce any seeds with a particular tet pollen because of
incompatibility problems - the tet pollen tubes are incompatible with
the pod parents style. The easiest way to check for diploids
producing unreduced eggs is to pollinate them with mixed tet pollen.
The easiest way to check for tet pollen is to look at the pollen under
a microscope. The tet pollen will be slightly larger and you will see
a cerain percentage of larger pollen grains.
There still is, however, the question as to if tetraploid hostas will
be anything significent compared to diploid hoasta.
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