TB: Tetraploidy
- To: "INTERNET:i*@egroups.com"
- Subject: TB: Tetraploidy
- From: S* M* <7*@compuserve.com>
- Date: Mon, 17 Jul 2000 22:40:13 -0400
R. Dennis Hager wrote:
>
Now that you've brought the subject up, was tetraploidy in TB's induced
by human intervention as it has been with daylilies, Sibs and JI, or did
it occur naturally? Since most bearded irises are tetraploid, how did
they get that way.
<
Let's just say that humans took advantage of a natural phenomenon.
European species [Ii. pallida & variegata, etc.] were diploids. Humans
found them. Loved them. Bred them. Came up with some very nice things
like the still-unmatched MME. CHEREAU.
Asian species[Ii. cypriana, mesopotamica, trojana, etc] were tetraploids.
I'll skip how they got that way, but it certainly wasn't human
intervention.
Collectors brought species from southwestern Asia into Europe and
hybridizers crossed the two types.
In a few cases, an undivided diploid gamete combined with a tetraploid one
to produce a first generation tetraploid. More commonly, though, the first
generation offspring were triploids -- few and of limited fertility.
Crossed back to tetraploids, though, they proved just fertile enough to
produce a few more tetraploids. Once there were enough tetraploids to
cross with other tetraploids, a new fertile family -- some call it an
artificial species -- was born.
That's the basic mechanism. I hope this simple explanation doesn't appear
to minimize the accomplishment. These pioneers were faced with a
significant fertility barrier and it took thousands of crosses by a number
of different people over a period of many years to complete the diploid to
tetraploid conversion.
Sharon McAllister
73372.1745@compuserve.com
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