Re: Prairie Iris Article Crossing Species
- Subject: Re: Prairie Iris Article Crossing Species
- From: g*@sasktel.net
- Date: Thu, 20 Jan 2011 01:56:37 -0600
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All very very interesting. Thank you for posting your comments on the
various subjects. I will have to try crossing lactea and typhifolia â such
a cross never crossed my mind.
Jim in Saskatoon
From: g*@peoplepc.com
Sent: Wednesday, January 19, 2011 5:47 PM
To: i*@yahoogroups.com
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
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