Re: HYB: inheritance of white

Linda, my understanding of the inheritance of white is quite a bit different
from yours.  Let me lay out what I believe is going on in "white" (non-blue is
a better way to say this, as the "white" as you point out can be pink, orange,
yellow or yellow amoena).

There are three kinds of non-blue ("white") irises:

1) Glaciatas from plicata breeding--where all of the anthocyanin is missing,
even deep in the hafts.  These breed luminatas, plicata/luminatas and plicatas
when bred to those that carry the pl genetic series.

2) Recessive whites, where the blue pigment is simply absent.  "B," the
violet-blue genetic sequence for forming blue or violet pigment (violanin) is
present in its recessive allele (same spot on the chromosome, just a variation
of the DNA) "b."  An iris "bbbb" is white (or yellow, etc.) unless a set of
co-pigments governed by different place(s) (locus or loci) on that or
different chromosomes, one or more, produces a light blue.  The pigment
studies reported in TWOI suggest that some light, clear blues are that color
not because of B (violanin) but because of other pigments.  In the past it has
been assumed a Bbbb iris is light or pale blue, with the color getting richer
with two, three or four "B" alleles (copies) of the gene.  Very few "bbbb"
whites exist.

3) Dominant whites (symbolized by "I" ("eye"--since that vertical line in the
font used in Outlook Express is ambiguous and looks just as much like an ell
as it does an eye.)  The "I" stands for "Inhibitor."  Purissima, Snow Flurry,
New Snow, Gudrun, Snow Goddess and all the vast number of whites (pinks,
yellows, yellow amoenas, etc.) that descend from them all are white, not
because of anything to do with the "B" genetic series, but because some
different place probably on some other chromosome starts a chemical sequence
that inturrupts the development of violanin, more or less.  I say "more or
less" as a number of ice-whites and light blues (such as Silverado) are "I"
whites.  Even some that are definitely not "white" to the eye may be "I"
whites genetically, especially if there is aphylla ancestry involved.

The dosage of "I" is rarely more than one or two.  Nearly all dominant whites
will breed some blues, half or one-fourth the progeny if bred to a non-white.
White crossed with white often will give about 1/4 blue or violets if both
parents carry only one dose of the "I" sequence.  Jean Stevens speculated that
PINNACLE, the pioneer yellow amoena carried three doses of "I" as it *never*
bred a violet or blue.  I can't speak to that personally.  I've never run into
a pink, yellow, white or orange that failed to throw some blue, violet or
blended seedlings, however few.  There was a speculation at one time that the
"I" sequence or gene had a fatal effect when present in large dosages--3 or 4.
Otherwise the number would build up.  It does not seem to.

So, if you want to get away from white, Robin, just go ahead an make your
crosses and pick out the seedlings that aren't white.  You'll usually get
about half from most "I" irises if you cross with non-whites.

The "I-sub s" (the "s" is a subscript), the factor that partially surpresses
violanin in the standards, top-downward, can build up to four doses with
progressively greater expression.  Fred Kerr's banded yellows are "Emma Cook"
types with several "I-sub s" factors present.  KEVINS THEME is an extreme
example of one factor only.  The amoenas with really white standards are those
with two or three doses present.  This factor is totally separate from the
dominant white "I" factor and can be present with it and comes primarily
through Paul Cook's iris PROGENITOR.

Neil Mogensen    z 7 near Asheville, NC

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