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?
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