Re: Tetraploids in Hosta

Rich:

>Question: In daylily hybridizing, you can cross tet x tet & dip x dip 
>(not sure about polyploids).  You cannot cross tet x dip or vice 
>versa.

In daylilies you CAN cross diploids with tetraploids IF the diploid is 
producing unreduced gametes.  Diploids normally produce haploid 
gametes.  However, because of some genetic mutations, some diploids 
produce diploid gametes.  When a cell undergoes meiosis it normally 
produces 4 daughter cells.  However, sometimes only two cells are 
produced and these have twice the number of chromosomes then what they 
should.  These unreduced gametes from a diploid look like a gamete 
from a tetraploid because tetraploids normally produce diploid 
gametes.  Thus, an unreduced gamete from a diploid X a tet is the same 
as a tet x tet cross.  What makes it nice in daylilies is that there 
is triploid block in daylilies.  That is, any triploids that are 
formed from diploid x tet crosses (haploid gamete + diploid gamete) do 
not develop, although there are some exceptions to this rule.  Thus, 
if you cross a diploid with a tet and get seeds the chances are pretty 
good that you have tetraploid progenies.  Unreduced gametes in 
daylilies are not difficult to find.

I'm not sure if hostas produce unreduced gametes, or if hostas have 
triploid block.  The problem in hostas is that there really aren't 
many well established tetraploids and also it's difficult to look at a 
tetraploid hosta and see anything that says "I'm a tetraploid."

Joe Halinar


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