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Re: ploidy article & Blue Coloration question


Andrew:

>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 
>today?

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.

Joe Halinar


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