TB -- Mesopotamica Influence
- To: Multiple recipients of list <i*@rt66.com>
- Subject: TB -- Mesopotamica Influence
- From: S* M* <7*@compuserve.com>
- Date: Sat, 17 Jan 1998 11:31:25 -0700 (MST)
Having been reminded that many
new people have joined the list since
our early discussions about the diploid
to tetraploid conversion, I offer this
brief -- and over-simplified -- summary:
1. Modern TBs are descended from
both European diploid species and
tetraploids from southwestern Asia, for
details of how this can happen, look for
discussions of the "Triploid Route" in the =
archives.
2. The first-generation offspring were
thus half European, half Asian, and fully =
fertile. If line-bred, their advanced =
generations would also be half-and-half.
3. Cold-climate hybridizers backcrossed to
diploids for gardenability and diversity
of patterns and colors, while warm-climate =
hybridizers backcrossed to tetraploids
for size -- and later hybridizers crossed things =
from the cold-climate and warm-climate lines
in hopes of getting the best of both worlds.
So we now have some cultivars that are less =
than half Asian and some that are more than
half Asian, in addition to the half-and-half that
we would expect.
Catch #1 -- the original conversion took =
place so many generations ago that we can't
trace individual cultivars to their original species.
Catch #2 --Although the diploid and tetraploid
species are highly cross-sterile because of =
their differing counts, enough of their individual
chromosomes are homologous that not only
are those rare first-generation offspring fully
fertile but theiradvanced-generation offspring =
function more like autotetraploids than =
amphidiploids. In plain English, today we can
be more concerned with individual genes =
than with chromosome sets.
The proverbial bottom line? What has all
this to do with I. mesopotamica? It is, by
reputation, the tenderest of the Asian
tetraploid TBs. =
Hybridizers who want to minimize its
influence can do soby analyizing pedigrees
and using breeding stock developed in cold, =
wet climates. Gardeners with cold and =
wet climates will benefit by choosing
cultivars from breeders in similar climates. =
If you want to know more, ask questions
or search the archives for species origin
of TBs.
Sharon McAllister
73372.1745@compuserve.com
