Good evening, El.
I'm not sure what you are looking for, exactly, and this is not the sort of
thing I know a lot about, frankly, but if you are wondering what will
cross with what, and how that happens, then some information on what has been
crossed successfully with what may be useful.
Appendix C of the book Garden Irises, published by the AIS in
1959, edited by Dr. L. F. Randolph, Is entitled "Check List of Iris
Species Hybrids", and, while dated as to what species are included, is pretty
comprehensive. It has been said by people who appreciate these things that
Garden Irises is the most scientific of the several books published by
the AIS. If you go to one of the various book search facilities on the
web--I use AddAll.com where I select the used book option-- you can find a
copy for not much money. Appendix D of the selfsame book is a listing of
chromosome counts of Iris species. Chapter 22 is entitled
"The Chromosomes of Iris Species," and it was written by Dr. Randolph and his
student, Jyotirmay Mitra. Dr. Randolph was President of the AIS and
a professor at Cornell.
Otherwise, the earliest fertility--or sterility--studies reported by
the AIS are those undertaken by Dr. A. B. Stout and his students at the New York
Botanical Garden, published in several AIS Bulletins in the interwar
years, notably July, 1925; Oct. 1926; Jan. 1927; April, 1928, and in
September, 1937, the latter, according to the title, being a discussion of
Ii. versicolor and laevigata, and the LA irises. This is the
same Dr. Stout who was involved with Hemerocallis.
I hope this is helpful.
AMW
-----Original
Message-----
From: Eleanor Hutchison <eleanore@mymts.net>
To:
iris-species@yahoogroups.com
Sent: Sun, Jan 2, 2011 6:14 pm
Subject: Re:
[iris-species] Chromosome Count
All I wanted was a simple explanation, so I thank
you, Dave!
I may end up checking out what crosses were already
successful, and give a couple a try.
El, Ste Anne, Manitoba, Canada
From: m*@msn.com
Sent: Sunday, January 02, 2011 4:26 PM
To: i*@yahoogroups.com
Subject: RE: [iris-species] Chromosome Count
Here is a very marginal answer. Somebody else here can probably get
more specific.
Even if the chromosomes are different in number, if the species
are closely related enough, they may hybridize with little difficulty.
Usually the species with the larger number has the same basic chromosomes,
little different from the one with fewer, it just has more of them.
Sometimes the ones with more are simple polyploids, having multiples of
the exact same chromosomes. Sometimes there are supernumerary chromosomes,
which are usually extra copies of one or more of individual chromosomes, or
which may represent a chromosome that split into two. Sometimes most or
all of two chromosomes might fuse together into one, to make a lesser total
number. Sometimes the numbers are shifted due to crossing of species that
have different base numbers that become combined into a new larger full set
(these may include duplicates, but they behave as if different).
Regardless of why the numbers differ, if the chromosomes match up well
enough, a plant can result from crossing two related species, regardless of
chromosome numbers. Sometimes though the chromosomes are different enough,
or enough errors occur in pairings, that some or all attempts at a given cross
will fail. Sometimes supernumeraries will join up with like ones to make
three-somes, sometimes the extras just hang around and don't pair up. I
don't know all the details of what happens with Iris, but they should follow the
same rules as most any other plants.
The next part of the question is "are the hybrids fertile". If there
are enough discrepancies in the chromosome pairings, or if there are other
incompatibilities, they may be unable to produce offspring, and end up being
basically genetic dead ends; or, at least the successes will be few and far
between. Sometimes if you can double the hybrid's number (if you can get
unreduced gametes), you can restore fertility with others that have like sets of
chromosomes (or when the hybrids are self-pollinated).
Sometimes in higher ploidies, there are so many copies of the same
chromosome, that the numbers start to become almost irrelevant, as long as some
full sets are represented in gametes, and can pair up when fertilized. (In
some groups of plants having just full sets seems to be more important to
fertility than it is in other groups of plants).
It can get pretty complicated when all the ramifications and combinations
are considered, but maybe this is enough to help a bit.
I need to learn more about chromosomes specifically as they occur in
Beardless Iris before I could elaborate more. I'm not even sure what the
base haploid number is for "water Irises", nor whether some of them have fused
chromosomes or supernumeraries in their compliments. It appears that the
ones you listed have very unrelated numbers, but when broken down more, they
probably would make more sense.
Dave Ferguson
in New Mexico
To: i*@yahoogroups.com
From:
e*@mymts.net
Date: Sat, 1 Jan
2011 14:17:35 -0600
Subject: [iris-species] Chromosome
Count
Can someone please give me a simple explanation on
hybridizing, using the chromosome count.
For example, I was just checking I. versicolor on
SIGNA, where it mentions the chromosome count is 2n=108. It easily crosses
with the laevigatae series, which has a chromosome count of 2n=32, while I.
virginica has 2n=70 or 2n=72, as does I. virginica var shrevei.
Thank you!
El
