Re: I. sibirica X I. pseudacorus

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I'm asuming you are asking abnout the fertility of the the IB's here. Not the actual production of one.

No one is actually absolutely sure about why there is fertility in the IB's from such a cross.  Most times the gametes formed are all mixed up.  The way the chromosomes divide up would depend on how much alike the sets are like the other set, the homology.  There is no way to tell that just by looking at it.   That is from experimentation.  One plant may tend to produce mostly SDB type gametes that have a full set of 8 and a full set of twelve.   Others may produce gametes composed of all TB chromsomes.

My experience with the aril quarterbreds has been this.  Most of them are sterile.  They are composed of one aril set, 10 (or 11) chromosomes and 3 TB sets.  So far all I've been able to get off of the few seeds I've gotten are halfbreds when crossed to other halfbreds.  You would think that you would get a few quarterbreds but the seeds either abort or don't survive in the garden for me to see them.  Most quarterbreds are highly infertile with other TB's (Capitola and Elmohr derived quarterbreds seem to be the exception based om the Registrations) even though the quarterbreds have three sets of TB chromosomes.  They seem to favor being balanced toward their overall genetic composition of half aril and half TB (i.e. losing a whole set of aril chromosomes seems to be a big deal).

Producing one is simple.  An SDB contributes a set of 8 and a set of 12.   The TB contributes two sets of 12.  Said and done.  You have an IB.  That is the foundation of the Class itself.

-----Original Message-----
From: dwiris@aol.com
Sent: Mar 6, 2011 12:12 AM
To: iris-species@yahoogroups.com
Subject: Re: [iris-species] I. sibirica X I. pseudacorus

 

I am interested in knowing what happens when you cross the amphidiploid SDB with a TB and get an IB?

 

Dorothy Willott

 

 

In a message dated 3/5/2011 11:26:18 P.M. Eastern Standard Time, pharcher@mindspring.com writes:

Example 2: SDB's are amphidiploids that combine the tetraploid chromosomes of MDB's (32) from pure I. pumila backgrounds and the 48 chromosomes of the TB's.  Each gamete will get one set of two sets chromosomes and two sets of twelve for a total of 40 chromosomes. When these plants form gametes the chromosomes divide the set of 16 I. pumila chromosomes into two sets of 8 and divide the 24 TB chromosomes into two sets of twelve. The set of 8 chromosomes pair up and the set of twelve pair up. The cell divides and each gamete will have one set of eight and one set of twelve for a total of 20 chromosomes.