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HYB: Punnett Square Question


Message text written by Donald Eaves:

>
I knew it wasn't usually used in the way I was trying, but it seemed to be
an easy fast way to put on paper what I might be looking for in the MARY
McCLELLAN cross (pod parent in this case).  Also, I thought it might be
a useful tool to use in a more conventional manner, in a simplified way,
and then see what appeared in the seedlings that don't fit.  Sort of a
slow learning method, maybe, but it probably would cause me to examine
the result and learn the answer for the difference.  Maybe a method for
determining the presence of recessive and modifying factors which might
cause variances.  That information might allow me to focus more
specifically.
I'm trying to use the square as a tool to progress with.  Possible?
<

Certainly.  The square can be a very effective learning tool.  By using it
to depict the possibilities, you  gain confidence that you've considered
all of them.  By comparing its predictions to what you've observed, you're
more likely to discover any erroneous assumptions before you've meandered
too far along the wrong path.  Plus, of course, the exercise itself will
prepare you for the more complex applications for which it was developed.

In the spirit of the hybridizing classes we held years ago when the list
was smaller and a greater proportion of our members were interested in
hybridizing, I'd like to suggest some "homework":  

1.      For each of the five types of tetraploids most often used to
produce arilbreds [AAAA, AAAB, AABB, ABBB, and BBBB], go through the
exercise of determining the type of gamete that will correspond with each
row or column of a Punnett Square.  [Tip:  I went through this step-by-step
for the ABBB-type in my previous message.]

2.      For each type, construct a square that represents a cross between
two individuals of the same type.  

The AAAA and BBBB charts will be so easy you'll wonder why I suggest doing
them [because that will help you see the overall pattern].  

The AAAB chart, like the ABBB chart I talked you through earlier should
help you understand why we call the unbalanced types "relatively infertile"
instead of dismissing them as sterile.   

The AABB chart should be enlightening, to say the least.  [Hint:  identify
the underlying assumption of the Punnett Square that does not accurately
represent amphidiploid genetics.]  

Then......   After you have acquired a better feel for the fertile families
and the relatively infertile groups, you'll be ready to tackle that
complete set of charts I mentioned earlier.  

>
As a new pollen dauber, I'm primarily driven by curiosity.  I am obviously
curious about those disqualified arilbreds.  Pat Norvell had a wonderful
speciman of SCARLET BUTTERFLY blooming in Dallas.  I was quite
taken with it and am itching to attempt a cross.  Unfortunately, the
blooms were in Dallas, not here.  The aril ancestry was obvious, though.
Those characteristics are not so obvious in MARY McCLELLAN, but
your comments about Tom Craig's selection preferences gives me a
bit more optimism.  Maybe MMc was just too good to not introduce,
or maybe he knew the parents and thus knew what he was seeing.
<

MARY McCLELLAN must be judged against her peers, not later generations. 
When this seedling was selected, substance, size and width were much-
in-demand aril traits.   From Craig's 1964-65 catalog:

"MARY McCLELLAN (Craig '52)
Spectacular iris clump; there is nothing to match this stately giant deep
blue.  Wherever iris grow, reports tell of its fine performance.  Bred and
selected among avocado trees, it is at home with papayas and mangos yet
thrives in the winters of Chicago, Montreal, and the Bavarian Alps where it
won a  performance test over top iris from all of the world for its ability
to produce long lasting flowers in great abundance on newly set plants.  In
1959 the Aril Socity International and The American Iris Society
established the C. G. White award as a medal given annually for the best
aril-bred in commerce.  Mary McClellan won the first medal with no close
rivals."

The published list of eligible candidates:
BLUE ELEGANCE
HEIGHO
HOOGIE BOY
HURRICANE
EVENSONG
LADY DOZIER
GREENMOHR
MOHR MAJESTY
PURISSAMOHR
ENGRAVED
MOHR GLORIOUS
MARY McCLELLAN
CORONATION TAPESTRY
ANYTIME
BELLA MOHR
CASINO
PERSIAN LACE (Pure Aril)
WITCH DOCTOR
MOHRHAVEN
CINNA MAC
PERSIAN BRONZE (Pure Aril)
GOLDEN GLADIATOR
SAFFRON CHARM
STRIPED BUTTERFLY
TROPHY 
NO MOHR

>
In any case, since the pollen parent was SATAN'S MISTRESS, which
also does not show strong aril traits, I am truthfully hoping that a more
obvious aril trait makes an appearance if I can successfully grow some
to bloom size.
<

With all of its aril ancestry from one species, SATAN'S MISTRESS is a good
candidate for experiments and I believe that korolkowii-like signal and
veining could show up among its offspring.

>
And what about markers?  In doing chromosome counts, would a known
aril ancestor's chromosomes have to have been recorded to identify such
a marker?
<

Yes, this is far more demanding than merely counting the chromosomes -- and
this message is already too long and too technical for most tastes.

Sharon McAllister
73372.1745@compuserve.com

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