Re: RE: HYB: Getting It Straight For the Simple Minded - RePost

Gosh, after reading this email, I feel so "simple minded".  As a newcomer to
the iris world, all I know about an iris is if I think it's pretty or not!
And I know how to grow the ones I like.  But I am glad there are others that
DO know  about hybridizing them!  You smart ppl just keep developing new
pretty ones and I'll just keep looking at them!!  Thanks!  Vicki Gatling


----- Original Message ----- 
From: "Neil A Mogensen" <neilm@charter.net>
To: "Iris-talk" <iris@hort.net>
Sent: Tuesday, May 10, 2005 5:42 PM
Subject: [iris] RE: HYB: Getting It Straight For the Simple Minded - RePost


> Steve, you have asked some questions about which I believe a number of
> others may also have a degree of curiosity.  I will make an attempt to
> respond "for the Simple Minded."
>
> There is a difficulty about reducing what is incredibly complex stuff to
its
> essential elements without making hash of what occurs in the conception
and
> birth of new plants from the sexual process.  Plants are not quite as
simple
> as animals, but the matter is actually pretty much the same except for a
few
> matters that make no difference as far as your question is concerned.
>
> Normal "simple" plants and animals have two matched chromosomes in the
> cell's nucleus for each chromosome in their basic set.  These are
"diploid"
> organisms, a word from Greek meaning simply "two-fold."
>
> The pollen and the egg are "haploid," also Greek, meaning "half-fold."
Each
> of those chromosomes is unique, and the "how many" is described as the
> "x=number," even though one often sees the expression misstated as
> "n=number."  I'll use "x" below.
>
> Old diploid bearded irises from Europe, like *I. pallida* or *variegata*
and
> the hybrids between them have an "x" of twelve.  There are twelve unique,
> different chromosomes in the set.
>
> With bearded irises, around 1890 or so a few irises collected in Asia
Minor
> (modern Turkey) and other areas scattered from Greece to Afghanistan and
> Kashmir on the border between Pakistan and India began to drift into
> circulation in England and France, and later in the United States.  These
> clones,
> species, or whatever (some confusion reigns about these identities),
several
> of which are still available, were larger, heavier plants, bigger blooms,
> but almost monotously blue-violet bitones in color .  AMAS is one of those
> collected clones, and is listed by a number of major growers for its
> historical interest.
>
> Many crosses were attempted between these Asiatics and garden varieties of
> bearded irises.  Very few of the crosses were successful, and when they
> were, usually only had one or two seeds.
>
> It turns out that many of these Asiatics have the same "x=12" of the
> European irises, but have a total of forty-eight chromosomes, where the
> older, colorful and hardy European varieties had only twenty-four.  They
> were "tetraploid," again, the same Greek, but with "four" as the first
part
> of the word.
>
> What happened to account for these one or two seeds is that something had
> gone awry during development of the occasional ova (or more rarely, the
> pollen grain) that was involved in these hybrid seedlings, and the result
> was a "tetraploid" hybrid because *all* of the diploid parent's
chromosomes,
> two of each, had gone into the ovum or sperm (pollen grain), and when
> fertilized with the Asiatic, produced colorful, beautiful, big hybrids
that
> were fertile.
>
> All of our "tetraploid" TB's are descended mostly from these hybrids.
>
> In a few cases, natural, wild tetraploids of *I. aphylla,* and *balkana*
> have entered into the mix, and some other diploid species such as the
dwarf
> *suaveolens,* *reichenbachii,* (which also has a tetraploid form, I
> believe), *imbricata* and others have been mixed in also.
>
> You may notice that Jim and Vicki Craig in Oregon have a line of
tetraploid
> Miniature Tall Bearded irises (which are a classification normally diploid
> in their chromosome makeup) that have been bred down in size by the use of
> normal Tall Beardeds with *I. aphylla* in complex pedigrees.
>
> None of this has depended on the chemical "boost" that colchicine has been
> used to double the chromosome counts in JI's and Siberians.  Tetraploid
LAs
> also exist.
>
> Your question about the arils and aril hybrids is a more complex one.  The
> "x" of Regelia (Hexapogon) irises is eleven, and that of the Oncocyclus is
> ten.
>
> Several decades ago various people in California and elsewhere began
trying
> to get hybrids between these aril irises from the Middle East, from Israel
> to Iran and Turkey and the bearded irises.
>
> By an extraordinary streak of luck a hybrid occurred sometime before 1910
> between the diploid Oncocyclus species *iberica* with twenty chromosomes
and
> the collected wild tetraploid Macrantha.  This produced a hybrid with all
> twenty of the chromosomes from the Onco, and the normal half of
twenty-four
> from Macrantha.  Following a rule no longer allowed, the species name and
> Macrantha were combined as IB-MAC, which has pollen that is quite fertile.
> It has forty-four chromosomes, four "x" counts, two each of the ten from
the
> Oncocyclus set, and two sets of the twelve from Macrantha
>
> When these chromosomes pair up to begin the process of pollen or ovum
> formation, the ten Oncocyclus chromosomes pair with the other ten like
> themselves, and the same thing happens with the twelve from the TB
> Macrantha.
>
> This behavior makes the plant behave as if it were a normal diploid with
an
> "x" of twenty-two.  However, that isn't what the hybrid is.  So a new term
> comes in.  This is "Amphidiploid," again using the Greek.  There are other
> amphidiploid hybrid varieties and a few species among other kinds in
irises.
>
> Modern ABs that are neither "+" nor "-" are only slightly more complicated
> than this.  They often involve a mix of chromosomes from the Regelias, the
> Oncocyclus and the various classifications of Beardeds.
>
> That evolution has had the hands of many heroic, extraordinarily patient
> people mixed in.
>
> Your comment, "Arilbred iris are crosses with various bearded iris and
aril
> iris. For the most part, these crosses are fertile" opens a Pandora's Box.
> The truth is, by far the largest majority of the early crosses produced
> hybrids that were as sterile as they could be.  It was only by
extraordinary
> persistance, and according to one source I ran across years ago, helped
> along through the throwing of IB-MAC into the mix, that the jump up to
> "amphidiploid" fertile hybrids occured. This history makes great reading,
> and I highly recommend it.
>
> Curiously, there are other possibilities than "tetraploid," by the way.
>
> If I remember rightly, edible modern potatoes are a product of some
> extraordinary collecting and plant breeding by South American Natives that
> involve at least five different wild species.  They are "Octoploid,"
meaning
> "eight-fold" in their chromosome makeup.
>
> Such things as "triploids" and "penta-" and "hexa-" hybrids of various
kinds
> also occur, including in irises.
>
> In animals, on the other hand, any combination above diploid is usually
> fatal.
>
> Neil Mogensen  z 7  Reg 4  western NC mountains
>
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