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Re: HYB: William Mohr Giant--an amphidiploid?

  • Subject: Re: [iris-photos] HYB: William Mohr Giant--an amphidiploid?
  • From: "Arilpums" arilpums@comcast.net
  • Date: Wed, 3 Dec 2003 16:38:14 -0800

I have Ajuga "Catlin's Giant" and last spring I broke up the clump to spread it around in parts of other areas of garden space. It truly is a giant compared to the normal size of Ajuga. There is one caveat. Altho it does not like our hot California sun it also does not like too much shade. The one clump was getting morning sun but the leaves were getting moldy. So I have planted them to moving shade and where there is plenty of air movement and they are now happy and growing like weeds. Glad to learn more about it. Thank you. The leaves are so large they look like spinach leaves. By the way is Ajuga safe to eat?
----- Original Message -----
Sent: Wednesday, December 03, 2003 2:20 PM
Subject: Re: [iris-photos] HYB: William Mohr Giant--an amphidiploid?

Since I am lazy I have copied some examples of mitotic conversion from an Alpine-L post here it is;
reprinted from: Alpine-L Digest

Steve Vinisky:
>I have heard of three other methods of attempting colchicine conversion on bulbs.

Steve is inciteful in mentioning these alternate methods of inducing tetraploidy with Colchicine. Here's some others for Iris:

        1. A mature fan is cut to the rhizome in summer and a small 'cup' is scooped out the rhizome. Dilute colchicine solution is kept in the cup for the desired period-keeping it full. Evenmtually new shoots may emerge fully tetraploid.

        2. Following pollenation, a hypodermic with cochicine is inserted in the base of the pedicel and appropriate cochicine is injected as the seed pod develops. Some of these sedds will produce tetraploid plants.

        Colchicine is not the only answer. Some folks use the very available herbicide 'Treflan' to induce tetraploidy. The cultivar Ajuga "Catlin's Giant' is supposedly a tetraploid that appeared at the edge of a large patch treated with Treflan, The central plants were all killed, but a single crown on the edge developed into this giant cv.

        There are a number of other chemical agents used to induce tetraploidy, variegation, flower doubly and other mutations. Handling any potentially mutagenic chemical has inherent dangers - beware.

        Any other chemical mad scientists trying other treatments?

James W. Waddick

I hope Jim will forgive me utilizing his post. Seedlings have already undergone fetrilization and the cell growth after that is mitosis.JIM's #1 would be closest to what may have happened naturally to 'William Mohr Giant'.

Neil A Mogensen <neilm@charter.net> wrote:

Robt R Pries suggests William Mohr Giant may have arisen from a faulty mitosis where the two sets of chromosomes (10 from *gatesii*, 12 from Parisiana) did not separate and a doubling occured.
This is not exactly what does occur in the colchicine and Oryzalin (Surflan) treatments, methods for which are published for use with tiny seedlings.  The doubling occurs due to a disturbance during meiosis, not mitosis.
There are natural tetraploid and amphidiploid hybrids that exist in irises.  The Asiatic tetraploids, such as *trojana*, *mesopotamica*, Amas and Ricardii among the TB's and *Iris pumila* among the dwarf bearded are examples.  We do not know *how* these arose, but in the case of *pumila* the parentage is apparent from the karyotype (an anysis of the morphology of the chromosomes), which reveals the ancestry to be hybridization from *attica* and *pseudopumila.*  The only karyotype I have seen published of an Asiatic tet is that of *kashmiriana*, and it resembles *Iris pallida,* even though the phenotype does not.
I do not believe polyploidization has ever been noted in garden irises except through seed--such as those like DOMINION which were from pods containing one or two seeds and involved the Asiatics on one side of their ancestry and diploid European beardeds on the other.  The great majority of these involve seeds forming on the diploid as podparent.  The reverse, the diploid registered as pollen parent, are rare but include SNOW FLURRY for one.
Since animal pedigrees put the male parent first and the female second, some early breeders may have followed that pattern.  Our conventional useage is the reverse--female parent first.  We do not know for certain who followed which pattern among the early hybridizers so parentages and their order is not always certain.
The significant point is--that there have been *no* recorded, recognized doubling of chromosomes or formation of fertile amphidiploids from diploids of any sort that did not involve a disturbed meiosis rather than mitosis resulting in a double-chromosome ovum--or more rarely, pollen grain.  This is true especially of diploid hybrids of oncocyclus X  diploid bearded--a category which includes a number of cultivars with histories sixty, seventy or more years long.  The only possible exception is "William Mohr Giant."
What I find disturbing is the apparent phenotype of "Giant."  The original, authentic William Mohr looks quite oncocyclus-like, has strongly recurved foliage and delicate but very distinct patterning of the *gatesii* type without smearing or shading.  The ground color is quite uniform, and the beard looking quite unlike a normal TB.  The photo of "Giant" does not show these characteristics.  The beard shows some yellow also, which the diploid William Mohr does not as I recall.
If "Giant" is found to be extant it would be a service if a chromosome count were made, and also the number of long metacentric chromosomes noted.  A true, doubled WILLIAM MOHR will have only two.  A "Mohr" "quarter-bred" in the old terminology, will have three.
Neil Mogensen  z 7 near Asheville, NC

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