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
Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.
[PHOTO] (iris-photos) SDB What Again