fertility of triploids

Toby Bradshaw toby at carson.u.washington.edu
Tue Dec 15 11:06:51 EST 1992


In article <1992Dec14.223517.26140 at cbfsb.cb.att.com> bky at cbnewsf.cb.att.com (william.a.stafford) writes:
>   Are all triploids always sterile?  I was planning try my hand at Magnolia
>breeding this spring.  In the course of doing some research on the plants
>that I had intended to use as parents I found that one was a triploid.
>   I was under the impression that triploids are sterile but I recently
>read that triploids of some plants can be self fertile and can also
>produce fertile pollen.

Like most things in biology, it depends.  Triploids derived from
true diploids are generally sterile because pairing problems in
meiosis yield unbalanced gametes.  If the plant species in question
is a functional tetraploid, though, "triploids" derived from it
will probably be somewhat fertile, since there are redundant
copies of most or all genes.  Of course, triploids can 
produce unreduced (3n) gametes, and these may be fertilized to
yield tetraploids.  The ratio of endosperm ploidy to embryo
ploidy plays a critical role in the development of some seeds,
so that such combinations do not always work.  Even if no seed
are produced, embryos may usually be rescued by growth on suitable
artificial media.  No doubt the horticultural literature is
loaded with information on this topic.  There are some magnolia
breeders at the University of Georgia; you might try calling
down there.

Toby Bradshaw                       |
Department of Biochemistry          |  Will make genetic linkage maps
and College of Forest Resources     |            for food.
University of Washington, Seattle   |
toby at u.washington.edu               |



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