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Crossing with triploids

>Is it possible to make crosses between triploids?

As a general rule triploids have VERY low fertility and pollen is 
usually non-viable.  However, some triploids will show some pod 
fertility.  In the genus Lilium, true lilies for those of you in the 
south where daylilies are often refered to as lilies, there are a lot 
of triploid plants and commerically the triploids are preferred.  Many 
triploid lilies will produce some vuable seeds when pollinated with 
tetraploid pollen and some are a lot more fertile then we would expect 
for a triploid.  Triploid x diploid crosses rarely produce seeds and 
triploid pollen is often unuseable.  My guess is that in hostas you 
will have the best results pollinating triploid hostas with tetraploid 

In lily hybridizing diploids are often pollinated with tetraploids to 
produce triploids and the triploids are then pollinated with 
tetraploids to bring diploid germplasm into the tet germplasm pool.  
This is possible because there is no triploid block that aborts 
triploid embryos.  The result of triploid x tetraploid crosses in 
lilies is almost always tetraploids.

In daylilies we have triploid block, so any triploid embryos that form 
from diploid x tetraploid crosses do not develop.  When you do get 
seeds from diploid daylily x tetraploid daylily they are tetraploid 
because of unreduced gametes on the diploid side.  A diploid normally 
produced haploid gametes, but, because of genetic mutations, some 
plants will produce diploid pollen instead of haploid pollen.  This is 
called unreduced gametes.  

Hostas probably have unreduced gametes because there are natural tet 
species.  However, this is disregarding that hostas are probably 
already ancient amphidiploids.  I don't know how many triploid hostas 
there may be, but I sort of got the impression from Ben's work that 
there are quite a few of them.  This would suggest that triploid block 
may not be present in hostas.  Maybe Ben can fill us in on how many 
triploid hostas there are?

Joe Halinar

Joe Halinar
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