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Re: Re: TB: IB X TB to get pumila spot into TB's ( From iris-photos)

I know it is very difficult, but it should be possible. You have to cross:
8+12+12+12 x 12+12+12+12
You get a very low seed set and will need a large amount of seedlings, but I think at least some of them should carry the Pumila Spot gene - right?!


Mike Greenfield schrieb:
Sending this for Chuck Chapman:

Fo some reason my posts to Iris-List don't seem be to going through,
so I'll post here.

The "Pumila Spot" may not be a genetic possibility on TB's. Pure
pumillas have four sets of 8 chromosomes as versus the four sets of 12
that are on the TBs. Our MDBs have three sets of 8 and one of 12.
SDB have two of each, IBs have one of 8 and three of 12.

TB's do have a spot pattern. This is called the "variegata spot" or
sometimes called the "Umbrata" pattern. You see this as a narrow edge
on the falls, ususally without any of the blue (anthrocyanin) on the
reverse of the falls.

Sometimes with situations like this, there can be matching of genes
from different species and cross overs, and in other situations there
can't be a crossing over, no matter what. the luminata allele of the
plicata series is an example of this. The 8 chromosome set of pumilla
carries the glaciata gene and only the glaciata gene of the plicata
series, and it hasn't been able to cross over despite the huge number
of opportunitities. Ther is an explination of why this is so, but it
is a complicated one that is a bit long to go into here.

So, basically, it would appear that the "pumila Spot", which is
basically a smaller spot then the "varietata spot" , basically would
appear to be on one of the uncompletely paired or unpaired chromosomes
and not have the opportunity to cross to the TB set of 12 chromosomes.

Having said this, I offer a few possibilities. A very tall IB. That is
a plant with 8/12/12/12 chromosomes that blooms at TB height. This is
possible, and I have produced such an animal.

The other possibility is to breed the "varietata spot" TBs and select
for wider margins on the spot.

Could someone cut and paste this to Iris-Talk as I'm unable to post
there right now.

Chuck Chapman




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