Triploids

John Montgomery wrote:

:  I am not a geneticist so please correct me if I present faulty information.
:  Several mentions have been made that triploids are sterile and therefore a
:  dead-end in hybridizing. I believe that there are examples in the
:  intermediate class which make this statement not strictly true. Is it more
:  accurate to say that the work is difficult and frustrating but not
impossible?

Yes -- that is much closer to my experience.  I like to think that there's no
such thing as a completely sterile iris, just those that haven't yet found the
right partner....   People who want lots of seedlings -- and want them RIGHT
NOW -- and people who don't want to take the time to learn about genetics should
definitely NOT bother with triploids.  But triploids have been instrumental in
the development of tetraploid strains.  For example, the conversion of modern
TBs to tetraploids and the development of modern amphidiploid arilbreds.   (I'm
sure others can provide more examples.)  Hybridizers who are want to develop
something new and different find the triploids can be a valuable tool.

:  Lily (here I go again) triploids are generally unreceptive to diploid pollen
:  but they generally will produce seeds from tetraploid pollen.

In iris, I've found that the triploids are usually most effective when used as
the pollen parent.  That doesn't mean they shouldn't be tried as pod parents,
just that the odds are best when triploid pollen is used on tetraploid flowers.

:  The seed set
:  will often be low but there usually will be viable seed. Sometimes (perhaps
:  the norm) in these crosses will be the production of a normal embryo but the
:  will be a lack of sufficient endosperm to allow full germination. In these
:  cases, embryo rescue techniques may be successful.

Also true for iris.

:  Not being one who
:  worships at the altar of tetraploidy, I find that the triploids often
:  exhibit the best characteristics of both.

Yes, indeed.  Triploids often make outstanding garden subjects.  So much so that
I often yield to the temptation to test their fertility....

:  Now to warp my argument a bit, has conversion to tetraploidy been attempted
:  for I korolkowii? 

Many years ago, a collected variant of I. korolkowii was counted tetraploid --
but it has apparently been lost.  Sam Norris may well have tried colchicine
conversion of I. korolkowii along with the oncos, RCs & OGs,  but I'm not aware
of any success with such experiments.  Anyone interested in conducting such
experiments would benefit from readling Norris' articles on the subject.

Sharon McAllister
73372.1745@compuserve.com
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