HYB: versicolor and beardeds

I might go a step or two further than Dave and say that hybrids between
bearded iris and *I. versicolor* are somewhere between improbable and
impossible.

The beardeds tend to fall into three major groups--true bearded (Eupogon),
and the two aril types, Oncocyclus and Regelias.  Hybrids between diploid
Eupogons and either diploid oncocyclus or possibly diploid regelias have been
made and are typically sterile, but some clones have been known to produce
unreduced gametes from time to time, allowing hybrids with Eupogons or other
tetraploid hybrids to be made.

Hybrids between diploid regelias and diploid oncocyclus have very limited if
any fertility unless unreduced gametes are produced.  This has occured and
resulted in fertile hybrids that include ancestry of all three types, but
primarily involve Eupogon and oncocyclus ancestry.

There has been at least one hybrid between a diploid Eupogon and a species of
crested iris (Evansia).  The hybrid demonstrates no fertility at all to the
best of my knowledge.

I know of no hybrids between Eupogon beardeds, either diploid or tetraploid,
and members of any of the beardless groups, including *I. versicolor.*

There is an evolutionary relationship between bearded and beardless irises,
but the separation of the types is so far in the past the lack of homologous
sequences of DNA in the chromosomes between any two combinations of types has
been blurred too greatly by mutations in the various sections of chromosomes
for any kind of pairing to form.  This itself should not prevent
hybridization, as the same can be said of PAL-TEC, the one known hybrid
between a Eupogon and an Evansia.

The fact that no hybrids between the tetraploid cousins of *I versicolor* and
tetraploid Eupogons says something more.  It suggests either that the
biochemical processes necessary for plant survival are not sufficiently alike
between the types for survival of a hybrid, or that the mechanisms of
reproduction are sufficiently dissimilar to prevent the mechanics of
reproduction of the hybrid to occur.

Hybrids across fairly broad gulfs of difference do occur between members of
various diverse and not very closely related beardless irises however.  *I.
pseudacorus* has been crossed with some somewhat related Japanese iris (*I.
ensata*) clones, but the hybrids are apparently sterile at the diploid level.
*I. setosa* has been enduced to form hybrids with more than one different
type.  Some of these have even shown some fertility, I believe.  Even odder,
"Sino-siberians" from China can form hybrids with the west coast natives found
in Oregon and California.

There are others who can speak to this question far better than I.  I just
find the question interesting.

Why can't such hybrids form?  What prevents them?  For that matter, why can't
we hybridize between, say, Gladiolus and Iris?  There is an evolutionary
relationship here also.

It seems to be possible to take segments of chromosomes from organisms and
insert them successfully into wildly unrelated life forms--such as from
bacteria into maise ("corn" in American English). or even stranger
combinations.

These kinds of "hybridizations" do not alter the basic biochemical processes
of life to a large degree, however.  Wholesale incorporation of the entire
genome of one species into another, even fairly similar and closely related
species seems to be chancy at best and often results in drastically reduced or
even prevents fertility.

Types as different as *I. versicolor* and the garden varieties of tall bearded
irises (one group of Eupogons) seem to be too different for hybrids to occur.

But--as Dave Ferguson points out--Who knows?  You may do something
"impossible" and never accomplished before.

Neil Mogensen    z  7   western NC

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