Re: Re: about the question(s)

In a message dated 4/29/2005 5:59:17 AM Mountain Daylight Time, donald@eastland.net writes:
This was a cross of siblings that were supposed to be MACHO HOMBRE X
KOKO KNOLL.  I've felt the cross was contaminated and think getting
these seedlings are an indication the pollen parent is wrong and the
seedlings a result of a contaminated cross.  The idea was this group
of seedlings would give some that resembled the grandparents.  That
hasn't happened so far.  All those that will bloom this year look like
the seedling parents and don't resemble MH or any other iris I've had
growing.  Still trying to figure out the cross.  Generally nice
plants, but haven't been easy podders and seldom produce pollen.  No
pollen at all this year, e.g.  These seedlings are following that
pattern as well, but all of them didn't bloom as first year plants.


In my work with quarterbreds, I've never recovered the "look" of a grandparent so I wouldn't declare your original cross contaminated on those grounds alone.  The reduced fertility actually supports the validity of the cross.  If the pollen parent had been a TB, I'd expect greater fertility.  Even some of the early C. G. White cultivars that were declared contaminated crosses by chromosome counts were found to have aril chromosomes by karyotype analysis.  So let's consider what factors could be in play if the parents really are MACHO HOMBRE X KOKO KNOLL.

The chromosome-set model is appropriate for beginning hybridizers.  I've often used it myself when a relatively simple explanation is called for.  But, to provide a quick analogy, it's like gradeschool arithmetic -- while you've now entered the more advanced world of probability and statistics.

By chromosome-set theory, your original MH-KK seedlings are type ABBB and thus produce both AB and BB gametes.  That implies a 1:2:1 ratio on recombination.  Nice, simple concept.  Black & white, no shades of gray.

Welcome to the real world.  Homologous/non-homologous is like black/white.  Today's tetraploid TBs wouldn't exist without the gray area in between.  If you look into writings about the diploid-to-tetraploid conversion and karyotype analysis, you will see that the key was that many species have some near-homologous chromosomes.

Yes, the homolgous ones pair.  The "leftovers" tend to pair with whatever is close enough, and the rest are distributed randomly.  Therefore, reduced fertility.  The result is not quite a normal distribution, in the statistical sense, but it's also not a 1:2:1 ratio.  Sometimes seedlings have just enough fertility to be useful.  The catch is that once you've "mixed up the genes" like this, it's next to impossible to sort them out again. 

As for the pigmentation questions, I can't add much to the earlier responses except to point out that when dealing with arilbreds we must cope with parallel pathways. The cross of CAPITOLA onto a dominant white TB was so common that the results are now predictable.  Otherwise, the only prediction I can make in crossing for quarterbreds or crossing between quarterbreds is to expect the unexpected.  

Decades ago, there was a study of recessive white TBs that determined there were at least two different types.  Crossing two cultivars of the same type produced only white.  Crossing cultivars of two different types produced shades of red-violet through blue-violet.  I don't recall who proposed the theory that these different mutations came from different ancestral species, but perhaps some of our TB experts can shed more light on the subject.

I have a hunch that the color pattern you obtained actually results from the interaction of TB and aril genes.  Can't prove it, of course, but urge you to keep it and experiment with it further.

Sharon McAllister
Yahoo! Groups Links
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index