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re: hybridizing and unanswered questions

Linda asks

:One of the more or less unanswered questions that has been asked a couple of
:times is what are the hybridizing goals of some of you? <snip> Tom, why
:are you crossing species?

I believe that most "big-time" hybridizers are interested simply in producing
"better" cultivars within the class they work with. In other words, if you
breed TB plicatas you just want to make one that will score better on
garden judging (or be a bigger hit with the public) than previous TB plicatas.

My personal goal is to expand some of the underdeveloped fertile families
with new genetic material, and follow that up with quite a bit of line
breeding to bring out the potential of the new genes. In particular--

1. The 48-chromosome medians. The TBs are 48-chromosome tetraploids, and
so are a *few* dwarf and median bearded species. It is possible to create
a whole series of medians, from SDB size on up, that are completely
interfertile with the TBs. Right now the IBs are essentially sterile, and
the MTBs and SDBs are isolated from the TBs and BBs by having different
chromosome complements. Expanding the TB/BB fertile family to include
irises that fit the other (smaller) median classes would allow all the
medians to benefit from developments in the TB class, and also allow
line-breeding of medians, which now can only be done with some of the
median classes, not all.

Most of the effort on this type of breeding has been done by Hager in
his tetraploid MTB line (30+ years in the making), and by the Craigs.
They have focused on using I. aphylla to bring smallness into the line,
and neither Hager nor the Craigs have really tried to select for *smaller*
(SDB size) medians in their lines. That's what I'd like to do, using
I. balkana, rather than I. aphylla, as the basis of the line--if I could
ever get my hands on it!

2. The aril-pums. This is a wide-open area of breeding. Practically
nothing has been introduced by anyone yet. Crossing tetraploid arils
with I. pumila will create a fertile family of arilbred dwarfs, MDB or
SDB size, but half aril and fully fertile. (Most of today's arilbred
medians come from crossing arilbreds with SDBs--they are only 1/4 aril
and essentially sterile.) These little guys might well prove to be the
most adaptable arilbreds for cold climates.

3. The 44-chromosome arilbred medians. Crossing tetraploid arils with
the 48-chromosome medians from (1), above, should produce a line of
arilbred medians that are fully fertile with the current CGWhite-type
tall arilbreds. This will make it possible to line-breed for arilbred
medians, taking advantage of all that's available in current arilbred
lines. This area is also completely wide open.

There's no Dykes Medal in any of this, but I think the iris world will
benefit more in the long term by the development of these new families
of irises than by incremental improvements in the TB family, which I
think is getting tired, genetically speaking.
:Around here, pollen dabbers look at what they have in bloom and decide what
:might make a nice cross.  Is that the approach of a lot of hybridizers?
: Before you say it Tom, I already know part of the answer to that question is
:an obvious yes! : )

Hmm. With the kind of hybridizing I do, my "plans" are not mostly about
crossing particular varieties, but about crossing representatives of
different major classes. Take the aril-pum line for example. I have about
6 different I. pumila cultivars and a comparable number of tetraploid arils.
The plan is to cross any pumila with any tet. aril. If I get lucky and
have so many open blooms and so much pollen that I can pick and choose,
I may try to mix colors (blue pumila/yellow aril; yellow pumila/purple aril)
to get as many different genes in the seedlings as possible. But that's
a secondary consideration.

In the tetraploid median line, I always try to cross a small thing
(usually that means I. aphylla or an aphylla descendant) with a pretty
thing (usually that means a modern-looking TB or BB). I. aphylla itself
is pretty ugly.

*Way* down the line, it might get far enough along to be concerned with
refining particular qualities in the line. At that point, I would plan
on crossing particular cultivars. But I think I'd still keep the mentality
of crossing say "a ruffly one" with say "a petite one", rather than tying
myself down to two particular clones. The idea is to have a concrete goal,
but use any and all raw material that can contribute to the goal.

But I don't go out in the garden and cross things just because they're
blooming--it has to directly contribute to one of the identified goals.

:I have no idea what kind of cross Dusky Challenger and Vanity will make, but
:I like them both and they are both in bloom, so I guess I will try it.

Go ahead. I can see it now--

VAIN CHALLENGER (Mann, '00) TB 30". Muddy yellow self. Resistant to rot.
Rot Queen Gardens 2001.

Seriously, though: Vanity carries an dominant inhibitor for the blue/violet
pigment family, and the pink is recessive--Dusky Challenger is unlikely
to be a carrier. The progeny will likely be whites and light yellows, with a
few blends too. Vanity seems to be a good parent for quality. Bringing
the pink out would take another generation or two of line-breeding or
back-crossing, and probably wouldn't be worth it.

:Are goals of hybridizers maybe a secret?  One of our older pollen dabbers
:says that some of the earlier hybridizers took to their graves what they had
:learned about heredity of iris characteristics.  At least none of you have to
:worry about the rot queen sneaking off with hybridizing ideas!

I think that was very true in previous generations, much less true today.
I think the AIS round robin program and other factors have produced a
rather cooperative ethic among iris hybridizers. Just the fact that all
the big-time breeders today publish their pedigrees says something.

Happy hybridizing, Tom.


Tom Tadfor Little         tlittle@lanl.gov  -or-  telp@Rt66.com
technical writer/editor   Los Alamos National Laboratory
Telperion Productions     http://www.rt66.com/~telp/

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