Variegated Foliage in TBs

Hi All,

First, I apologize for not getting this information out sooner, but America
On Line is down again in Salt Lake City.  I'll probably have to look for a
new service since AOL appears to be incompete.

My knowledge of variegated foliage (VF) in iris is limited to bearded iris so
please keep this in mind as you read the following.  I've been trying to
choose the best way to group information on this topic and have decided on
the the following catagories:VF species iris; variegation in tetraploid iris;
 hardiness of VF TBs; and hybridizing VF tetraploids.

The two VF species iris I'm acquainted with are I. pallida variegata
argentea, with white and green foliage, and I. pallida variegata aurea with
its cream and green foliage.  In the U.S. the cream and green is frequently
sold under the commercial name of "Zebra".  Most people assume that both of
these iris are diploids, but there is very strong evidence that Zebra has
both diploid and tetraploid clones.  Thus it's reasonable to refer to "three"
VF species iris.  All three are basically pod infertile with only a few
mishapen seeds produced.  However, my clone of Zebra is very fertile as a
pollen parent to tetraploid bearded iris.  The most significant point about
the species iris is  the variegation is STABLE!   The white or cream forms
the inner half of the leaf with the green on the outer half.  The colors are
on both sides of the leaf.  This characteristic has so far eluded hybridizers
of modern VF tetraploids.

The variegation of modern tetraploids: STRIPED JADE (TB), BOLD STRIPES (TB),
STRIPED BRITCHES (BB), ZEBRA BLUSH (TB), and my new ''97 intro., ZEBRA HALO
(TB). isn't stable.  The areas of white can be in streaks, marbled, or any
combination of the two.  The patterns vary from leaf to leaf and frequently
even side to side on the same leaf.  The amount of white on the increase will
vary also.  Some increase will be all white and will eventually die because
of their lack of chlorophyll.  Other increase may be all green and should be
removed from the plant.  Since the vigor of the fan is usually proportional
to its ratio of green, all green fans will eventually choke out the
variegated ones.  Most fans which have a ratio of 60% green to 40% white can
be both attractive and vigorous.

The hardiness of VF tetraploids can be a problem, but not because of the cold
winters.  I live in zone 6 and most of my VF seedlings do just fine while
they are dormant in the weather.  The real problem can occur in the spring
after the new growth starts.  The areas of the leaf lacking chlorophyll are
more susceptable to frost damage and this damage also destroys the veins
needed to service the green portions of the leaf.  One or two hard frosts
during the spring can really set these iris back.  This frost damage then
leads to the next problem which is bacterial soft rot which can start in the
frost damaged portion ot the leaf.  My experience is that during periods of
rapid growth in the spring the white portions of the leaf can tolerate
temperatures around the mid twenties; whereas, the green portions usually
tolerate the low twenties.

I hope my frank discussion of hardiness doesn't prevent you from at least
giving these very attractive iris a try.  In 8 years, last spring was the
first spring where frost  caused much damage.  The good news is that this
year's intro, ZEBRA HALO, was one of the only VF seedlings which DIDN'T
sustain frost damage.  I'm hoping this means I have improved hardiness in my
line.  

Finally, hybridizing for VF tetraploids.  It's All Mother's Fault!!  The DNA
for chlorophyll is NOT located in the nucelus of the cell, and only the ovum
producing parent (pod) supplies the DNA necessary to produce chlorophyll in
the seedlings,  The white areas within the leaves is cause by defective
chlorophyll, thus only the pod parent can pass this trait to its seedlings.
 The pollen parent plays no role.  Of course, it is posible to get a seedling
whith defective chlorophyll from and all green pod parent, but these
seedlings usually lack all chlorophyll and quickly die.  

It is hard to predict just what the seedling's chlorophyll composition will
be until you've raised many crosses from the same pod parent.   Usually, most
of the seedlings will be either all white or all green with an occasional one
which shows variegation right from the start.  A good breeding pod parent is
one which yields about an even split of all green and all white with maybe 5%
VF.  You wouldn't need to grow very many seedlings if you only transplanted
those showing variegation, but if you did that, you would miss out on the
seedlings developing variegated AFTER they are lined out.  I can normally
double the yield of VF seedlings by lining out all the green seedlings and
wait to see what develops.

Finally, A word about the flowers on VF iris.  The low yield of seedlings
with VF means you can't be overly choosy about the flowers. bud count or
branching.  With time each of these features will improve if enough
hybridizers work with them.  All the iris named above have "good flowers" and
bud count. The one exception is ZEBRA HALO which has an excellent, laced
flower on show stalks: HOWEVER, it is single socketed.  Oh, Well, one step at
a time!

Hope this helps,
Brad Kasperek
ZEBRAIRIS@aol.com
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