Annette,
No need for anyone to apologize for a slip - I do it all the time -
for me it comes from writing in the middle of the night after a long day at
work. As for 'Lady Emma', calling it an IB brought out an interesting
discussion.
Linda,
There are lots of good discussions about chromosomes and the results of
crossing various classes and/or species with differing numbers. I think
the 'World of Iris' has some good discussions on the basics. Again I am
away from my resources, so I still can't look up 'Lady Emma', nor cite
references.
Anyway, here is a bit of an "in a nut shell" summary, that I hope makes
sense:
The IB class is mostly derived from crosses between 40 chromosome species
or dwarf cultivars with 48 chromosome TB species or cultivars, yielding 44
chromosome (give or take one or two) IB offspring. The old IB cultivars
are mostly derived from I. lutescens crossed with 48 chromosome TB species or
cultivars, and certain hybridizers such as Sass and others made bunches of
these. Newer ones tend to be from TB cultivars crossed with SDB
cultivars in search of desirable character combinations from the two
parental classes. Of course they are all interfertile, so they are
crossed with one another too.
Some of the 40 chromosome dwarfs (I know the plural of dwarf is dwarves,
but it sounds wrong for Iris somehow) are hybrids of 32 chromosome dwarf
species or cultivars with 48 chromosome TB species or cultivars, and I.
lutescens and other wild 40 chromosome species of bearded Iris also probably
derived originally from 32 chromosome species crossed with 48 chromosome
species. This is overly simplified, as 18 and 24 chromsome species
(diploids) may have been involved too - through unreduced gametes.
Anyway it sort of works out like this:
(32/2) + (48/2) = 40 This lead to wild species such as I. lutescens
and most cultivated SDB's (which are fertile with species such as I.
lutescens)
As for wild candidates there are a lot, but potential examples could
be as follows. It is likely that the parent species of the original wild
40 chromosome species were those that occur around or near the Mediterranean,
but things to move around over time. It seems that more notherly or
inland small or smallish 24 and 48 chromosome species such as
I. aphylla, I. croatica, I. junoniana, I. reichenbachii, I. suaveolens, and
their kin. probably weren't involved. Probably not I. variegata either,
though perhaps. Also, these (except for I. variegata, which was
important) mostly weren't involved in early cultivars either, but they are
more and more now:
I. attica (unreduced = 16) + I. pallida (unreduced = 24) = 40
or
I. pumila (normally reduced 16) + I. cypriana (normally reduced 24) =
40
These could be examples of how wild species such as I. lutescens came to
be. They are fertile, because they have two sets of 8 and two sets of
12, which act as if they are two sets of 20 (everything is ballanced).
They are technically tetraploids, but functionally they are diploids.
This is one way that chromosome numbers can be instantly and greatly increased
through addition of unlike sets to form new sets.
These tend to be dwarf (mostly SDB), but not as dwarf as the parent
species (mostly MDB) with a base set of 8 chromosomes (the 16 and 32
chromosome species).
When you cross the 40 chromosome plants with 48 chromosome plants, you
get an unbalanced set of one 8 and three 12's (usually - sometimes it
doesn't all sort out quite right and you get 43 or 45, or even occasionally
numbers futher away from 44, all the way from 40 to 48, because sometimes
things don't sort out quite as neatly as you might expect). Anyway,
these usually end up with 8 + 12 + 12 + 12 = 44, and they are usually
intermediate to SDB and TB, yielding mostly IB plants. The wild
"species" I. germanica, I. albicans, I. florentina, etc. are of this sort of
ancestry as well. They tend to be infertile (they will make some seeds),
and due to their most common ancestries they tend to be early flowering.
The MTB's tend to fall nearly all into two broad categories. One is
the diploids (nearly 100% of older cultivars) derived mostly from I. variegata
and I. pallida cengialtii, with a bit of other smallish diploid species such
as I. reichenbachii mixed in occasionally. They tend to be
late-flowering with more delicately proportioned stems and flowers than
the 44 chromosome class of (mostly) IB's, and they also tend to have
morphological traits dominated by I. variegata, while the 44 chromosome class
mostly look morphologically most like I. germanica or I. albicans (ignore the
flower colors).
The other mostly recent MTB group is very different and is derived from
cultivars of 48 chromosome TB's and BB's (BB's are usually genetically TB's,
but they just don't get as tall), crossed with small northern 48 chromosome
species such as I. aphylla, or cultivars derived from them. They tend to
inherit an earlier bloom time from the small species and some flower almost as
early as the 44 chromosome group, and often much earlier than most of the
diploid MTB's.
All the AIS categories tend to follow basic genetic groupings, and so
MTB's tend to be mostly 18 or 36 chromosome plants. SDB's tend to be
mostly 40 chromosome plants. IB's mostly 44 chromosome plants of recuced
fertility, and TB's tend to be 24 or 48 chromosome plants. There are a
number of dwarves that are 24 or 48 chromosome plants, but they tend to be
mostly wild northern species or species crosses, and not to be too much
involved in hybridization of cultivars (yet).
The MTB's are mostly 24 chromosome plants close to I. variegata, but now
there is a second group of them that are 48 chromosome plants of a different
ancestry.
TB's (and BB's) are mostly 48 chromosome plants of Mediterranean / Near
Eastern species often with I. variegata and/or I. pallida ancestry. But
many old ones (usually smaller) are 24 chromosome plants, closely akin to the
MTB diploids, but usually with as much or more I. pallida than I. variegata in
their ancestry.
The problem with the AIS system is that it only uses measurements as a
guide, and plants are inherently variable. So, sometimes a 44 chromosome
plant that would logically be an IB by genetics, will be a MTB or SDB by
measurement. So, they get classed with plants that are not similar in
chromosome make up. The same with 40 chromosome plants. Even
though they are genetically most like most SDB's, they can be larger or
smaller than average, and become MDB or IB by AIS registration.
As the years go by, the ancestries get more and more mixed up, muddled,
and genes blended together in new combinations. However, it is very
difficult to get the chromosomes of the base 8 species into plants with base
12 chromosome numbers and visa versa, because once they are mixed, they don't
tend to cross back to either main parental group very easily. The 40
chromosome intermediates are fertile, but in effect they are isolated from
either parental group by their new chromosome make-up. When they are
crossed with the parental groups in either direction they tend to yield
sterile plants with +/-44 chromosomes or +/-36 chromosomes.
The 36 chromosome class doesn't seem to be well-developed, but they
should be mostly MDB plants, and I'm sure there are a lot of them out there
that just haven't been recognized as such yet. They may even be some of
those "problem" parents that don't make fruit or pollen well, for
"unexplained" reasons. These would mostly come from a cross of
(32/2 = 16) + (40/2 = 20) = 36.
The more backcrosses are tried, the more will be successful, and the more
the chromosomes will get recombined in cultivars eventually. Some day
there may be MDB with 32 chromosomes, but with genes from TB's and
visa-versa. Also, the more new species are added to the mix, the more
complicated, mixed up, and interesting the cultivars will become.
And this doesn't even consider any of the Psammiris, Regalias, Arils,
etc., which can and are gradually being added to the mix too.
Dave
----- Original Message -----
Sent: Sunday, October 09, 2005 9:18
PM
Subject: Re: [iris-photos] RE: OT: ID a
Tree & rebloom news
Dear Dave
Excuse me for interrupting,
but all this info is just making my head swim. I have great
interest
in understanding the affects of the chromosome counts and hope
to educate myself to help me to cross more effectively. Can you
suggest any reading material to help me with this? Thanks
much
Linda in TN
Lascassas that is::::::: :)
Just to be a bit of a rebel here.
'Lady Emma' resides
with the old IB's in my beds, where it fits in quite
nicely.
Regardless of registration, I consider 'Lady Emma' to be an
IB, but my definition does not restrict itself to only measurements of
stalk and flower, and I am more concerned with the plants than what the
lists say. I don't remember the chromosome count of 'Lady Emma', but
I believe it is of the 44 (or close) type of ancestry and it's behavior
(early flowering, reblooming) and morphology are not like the older
diploid MTB's. It flowers a full month to even six weeks before the
diploid MTB's here. The newer tetraploid MTB's (different ancestry)
may have a similar calendar to 'Lady Emma' (but still not quite as early),
but they are quite different too.
I know that 'Lady Emma' appears
in most lists (including the AIS check list?) as an MTB, and so will
continue to appear in sales lists and shows as an MTB.
I don't have
my AIS checklists, the chromosome count, nor the parentage of 'Lady Emma'
handy; so, these comments have the uncertainty of being from memory
too.
Please correct me if any of this is wrong.
Dave
----- Original Message -----
From: Laurie Frazer
<mailto:lauriefr@localnet.com>
To:
iris-photos@yahoogroups.com
Sent: Sunday, October 09, 2005
8:07 AM
Subject: Re: [iris-photos] RE: OT: ID a Tree &
rebloom news
On Oct 6, 2005, at 10:30 PM, tmilchh@aol.com
wrote:
The only rebloom I have had is LADY EMMA , a yellow
IB with 4 stalks blooming. I want more!!!!! I will keep an eye
out for ROSILIE FIGGE. She bloomed this Spring for the first
time. I also want bloom on DAUGHTER OF STARS , BABY BLESSED
(IB)
Just to help you keep your
records straight, Annette, LADY EMMA is an MTB, and BABY BLESSED
is an SDB.
I sure wish I could enjoy rebloom up here, but
it's rare, indeed, that any iris can manage such a feat here in
zone
3b.
Laurie
---------------
lauriefr@localnet.com
http://www.geocities.com/lfandjg
http://www.angelfire.com/mn3/shadowood/irisintro.html
USDA
zone 3b, AHS zone 4 - northern Minnesota
normal annual
precipitation 26-27"
slightly acid, potassium deficient, clay
soil
