ï
AMW
You are certainly not ignorant or tedious as you
have sorted directly to one of the key issues.
To directly answer your question as I understand
it. Yes. Theoretically one can self a hybrid to "genetic" homozygosity
such that one of the originating parents of the hybrid is duplicated, stabilized
genetically, and breeds true from seed from that point forward. However, that is
an insufficient answer.
In practice, the probability of recovering a
specific known genetic constitution, ( presuming one knows what it
actually is from genomic data - which we don't ), from a hybrid source
and fixing those genes and alleles by selfing is an astronomical longshot.
Even with only 21 allelic pairs, the possible kinds of gametes that are produced
in the F1 from a diploid are somewhere around 2 million as I recall. That
expands to something over 10 million possible genotypes in the F2
where maximum genetic recombination and genetic diversity
occurs. Taking that to the tetraploid level expands the probabilities to
numbers my head can't hold. Further, considering that an iris has many more
than 21 allelic pairs, it is safe to say that recovering a specific
known genetic constitution is practically impossible with selfing and
re-selection from even a simple diploid source.
Having said that - your question differs
slightly. The probability of recovering your more broadly defined,
"individual which was identical to the the parent in so far as horticultural
interest goes", would have a considerably higher probability of success - still
no walk in the park ! One needs to grow a large enough population size
to have all the recombination types present in the F2 to select from.
Also, selection must be effective in the next 6 or 7
generations. Eventually you can get to your stated goal with
a stable true breeding genotype that makes the repeatable phenotype
you define. The critical piece in this process is that one
is selecting indirectly on phenotype unless you have a molecular
laboratory to identify genes and alleles of interest. Phenotypic
selection also allows additional environmental influence to creep in. That
is why growing selection subjects to perfection is a useful tool in improving
selection efficiency, even with simply inherited traits.
So, I suggest the most appropriate reply
to your question is theorectically YES and practically NO.
You Are Welcome.
Separately: may I digress . . . ?
One of the original reasons for my post was to
comment on seed vs. vegetative propagation. Seed propagation
follows classical Mendelian genetic segregation principles. Vegetative
propagation simply copys a plant. The genetic constitution does not change.
( another caveat - yes, mutations happen - relatively
rare ) Unfortunately, the seed vs. vegetative propagation issue often
gets "Schlumped" together in genetic conversations. Seems to me that vegetative propagation is a significant issue
in iris history and current breeding. The ease of indefinitely
perpetuating single plants from clones reduces the NEED for efficient seed
production. The way we currently grow commercial iris from clones, many
reset annually, also puts the premium on identifying genetics
that increase with high vegetative efficiency. This probably has more
influence than we known on iris population genetics.
For what its worth.
Zone 5 - snowin' and blowin'. No iris will be
growin' for a while yet.
irisman646
----- Original Message -----
From:
C*@aol.com
To: i*@yahoogroups.com
Sent: Thursday, January 20, 2011 8:58
AM
Subject: Re: [iris-species] Prairie Iris
Article Crossing Species
I'm sorry to be tedious, but I'm pretty ignorant, and I have a question
about the observations in your "Caveat."
Are you saying that, if one selfed a genetically complex
hybrid bearded garden iris--one which was fertile both
ways-- "successively for several generations" one would or
might produce an individual which was identical to the parent in so
far as horticultural interest goes, but came true from seed, so that
the traditional vegetative mode of propagation, partition of the
rhizome, would not be necessary, for one could simply cross at will
and sow a line of whatever whenever demand was there, presumptively for
years and decades?
I did not think it worked that way. Am I wrong?
Thanks.
AMW
-----Original
Message-----
From: gndavis@peoplepc.com
To:
iris-species@yahoogroups.com
Sent: Wed, Jan 19, 2011 6:47 pm
Subject:
Re: [iris-species] Prairie Iris Article Crossing Species
ï
May the record be gently corrected on triticale
?
The manmade "origin
of triticale" breeding model has certain affinities with
apparent iris species origin, as the following will hopefully
show.
Triticale is a manmade hybrid of triticum (wheat)
and rye (secale), thus amphidiploid. It does not involve barley. The first
such "primary hybrids" used wheat as the berry parent and rye
as pollen parent. The first generation progeny is a uniform F1
hybrid that is almost always male sterile. However, manmade
induced tetraploids from the F1 can be converted
from amphidiploid ( 2x genomes ) to tetraploid ( 4x genomes ) by
doubling with colchicine or other compounds. This will
often restore partial fertility and permit perpetuation of the breeding line.
In practice, especially in grain crops where optimizing fertility is critical
to grain yield; it is necessary to inter-breed these new
partially fertile progenies for additional cycles to fully optimize grain
yield through favorable recombination and
reselection. Further, these resulting fertile families must be
selfed to homozygosity if a true breeding inbred line is desired.
This is seldom appreciated. As a result,
most commercial triticale varieties are many many generations removed
from the initial wheat / rye cross.
It is often assumed that 2X diploid chromosome sets from the ancestral
sources are represented equally in the final fertile 4X
converted line. We have strong historical observations and some genomic
data that this is seldom if ever true in triticale and maize wide
crosses. I believe the same is true in iris. Since segregation
is often impaired in wide crosses, it is probably safer to assume
unequal genome representation. Many have reasonably speculated that this
is why two or more wide crosses made with the same pair of
individual plants can generate distinctly different sets of
progenies. Uneven segregation and representation of native
chromosomes and genes
during recombination is likely cause.
This is a general description of process in
triticale that correlates well to some proposed iris species origins and
directly to wide cross iris breeding.
CAVEAT: be careful not to confuse
vegetative plant propagation of iris plants with seed generations described
above. Vegetative propagation simply clones or carbon copies a
specifc plant regardless of whether it is a hybrid or inbred. Seed
generations on the other hand reshuffle genes each generation. A line
must be selfed successively for several generations to
become genetically true breeding.
Actually, I doubt there are many true
breeding iris. We make a cross, or mother nature makes a cross, and
we like it. Presto - since its an iris and easy to vegetatively grow we
clone it and circulate it directly.
Even in species iris seeds
circulated it is very doubtful if many (any?) are fixed
true breeding lines. The phenotypes may be similar, but genotypes are
likely still unfixed and can be mined for sheltered recessives and
re-shuffled for additional gene re-combinations within the source
line.
So, I'm gettin' round to say I believe
Charles Jenkins observations noted below.
And also . . . try lactea wiiide-cross with
typhifolia. Believe I got a few seedlings with that wide cross a few years
ago. They later collapsed in the seedling stage. I should have embryo
cultured them in a sterile environment but didn't do it.
irisman646
----- Original Message -----
From: g*@molalla.net
To: i*@yahoogroups.com
Sent: Wednesday, January 12, 2011 10:11
AM
Subject: Re: [iris-species] Prairie
Iris Article Crossing Species
ï
Added Note...Charlie Jenkins was a geneticist that work on
the triticale wheat in Canada. A cross of wheat and
barley.
So I would believe his results as he was very
meticulous.
Will
----- Original Message -----
From: r*@embarqmail.com
To: i*@yahoogroups.com
Sent: Wednesday, January 12, 2011
6:36 AM
Subject: Re: [iris-species] Prairie
Iris Article Crossing Species
I have been distracted lately trying to fix a problem with the Iris
Encyclopedia so I hope I am not saying something that has already been
said. Iris lactea has not been tried with many other species in
hybridizing. But Charles Jenkins who was geneticist and hybridizer of
spuria irises tried it with the spurias. He got very strange results and
if it would be anyone but him, few would have believed it, The first
generation he got plants that looked no different than the lactea he used.
But Charles did an F2 and to his surprise resulted in many of the
seedlings being twins out of the same seed. Each twin produced one plant
that looked like the lactea and one that looked like the spuria. Charles
was a very meticulous scientist and I believe his results but they
are certainly remarkable.
If you want to know what things a species has been crossed with there
is two sources you can go to. The later SIGNA checklists listed all croses
with a species and the Iris Encyclopedia has all of this information also.
Much is not formatted well, because I have not finished with all that
work, but it is all there I think.
----- Original Message
-----
From: g*@sasktel.net
To:
i*@yahoogroups.com
Sent:
Wednesday, January 12, 2011 1:04:27 AM
Subject: Re: [iris-species]
Prairie Iris Article
Hello El,
Did you come up with a list of what will cross with it? I have
always wanted to try crossing it with I. missouriensis which it kind of
resembles. In truth I think it is worth trying to cross it with
anything really. I does set seed quite easily and if you wanted to
make sure of a wide cross you would have to protect the cross.
I think BJâs poem has a lot of truth in it for the prairies â cold
tonight.
Jim
From: e*@mymts.net
Sent: Tuesday, January 11, 2011 9:25 AM
To: i*@yahoogroups.com
Subject: Re: [iris-species] Prairie Iris
Article
Morning Jim and all.
It took me a few minutes to recall which
magazine article you're talking about. I do now remember reading
that about lactea in your article. You could always get the editor
to post one of those corrections.
Interesting that you mentioned lactea though,
as just yesterday I was trying to figure out what crosses with it. I
got an OP seed pod off mine this past fall, but I'm pretty sure there was
only 1 bloom stalk this year. Perhaps it crossed with
itself.
El, Ste Anne, MB Z3
From: g*@sasktel.net
Sent: Tuesday, January 11, 2011 1:27 AM
To: i*@yahoogroups.com
Subject: [iris-species] Prairie Iris Article
To all of you who may have read my article I hope you can forgive me
for mistakenly putting Iris lactea in the Spuria group. I misread a
description of this Iris which lead to such a result. I was hoping
someone would take some editing license with the article.
Jim in Saskatoon
