Re: REB: genetics, origins
iris@hort.net
  • Subject: Re: REB: genetics, origins
  • From: L* M* <l*@lock-net.com>
  • Date: Tue, 07 Feb 2012 10:12:34 -0500
Thanks very much Chuck.
Betty also reminded me of the chapter on rebloom in TWOI (The World of Irises), by R. G. Smith, which I hadn't read for years. He defines rebloom as more than one blooming stalk produced on a rhizome that bloomed in the spring. He excludes cultivars 'whose stalks emerge serially over an extended season, as well as [those] ..with only a fraction of the mature [?] rhizomes blooming during one period and the remainder during the next [in the same year?]".
I'm not sure if this is a more narrow definition of rebloom than is currently accepted, but if it is still defined that way, I guess I'm not just interested in rebloomers, but also the other two types. IMM doesn't seem to fit the narrower definition - she produces a huge number of increases, few of which mature fast enough here to bloom at the same time, other than in spring. Unusual to see even much fall bloom from her here.
According to page 142, rebloom has been reported in a long list of species, so I guess the answer to my question re: species source is that there isn't likely to be one particular species that has provided 'rebloom' genes, but might be from several different species with one or more selections that rebloom in various breeders lines. 

Or were the same selections used repeatedly by early rebloom breeders?
TWOI/Smith says "the attempts of early hybridizers to create new rebloomers [presumably using some of these species selections?] have been fully chronicled (Rundlett 1958, 1959).
Unfortunately, the citations don't match up with the bibliography - Rundlett 1958 is there - Remontant Medians, The Median pp 49-52. No 1959 article, but 1965, Indermediate Rebloomers, Medianite 6:32-34; and 1971, Whence the Remontants, The Reblooming Iris Reporter 19:20-25, are cited instead. 

Anybody know if copies of these articles available somewhere?
p.139-140 of TWOI says G.P. Brown's rebloomers originated with a cross of a 'diploid [maybe variegata or pallida? doesn't say if it's TB or dwarf] of his own origination with the tetraploid Autumn King'. That was crossed with AUTUMN ELF (?some kind of dwarf? species?) to give SEPTEMBER SPARKLER, progenitor of his rebloom lines. 

On 2/3/2012 6:08 PM, Chuck Chapman wrote:

There are no rebloom genes per se.


All the genes involved in timing of

blooms ...control blooming as to
when plant is most available to support bloom (plant maturity) and
conditions are appropriate ...and...
to prevent bloom in fall when no time to mature seed

There are no daylight photo-period control genes for most iris. ...
Most iris species have vernalization genes, requiring a cold period
before plant is released to bloom. There are variation in vernalization
genes.



Some species HAVE to have vernalization before they can bloom. This is
called "Obligatory" vernalization. Lets call this gene vo.


Some plants from Mediterranean

climates have vernalization genes (an allele on vernalization gene site)
that can sense time since
"bud set" and after about five months will initiate spring growth as if
plant had a winter but wasn't cold enough for proper vernalization. ...This is called "facilitative "
vernalization. Lets call this gene Vf . A plant with one copy of this
vernalization reblooms in warm climates such as California, but not in
other climates.

Some species, specifically alphylla, don't have a vernalization gene.
They have a short day triggered winter dormancy gene, involving dropping
of leaves. You can see them go dormant and leaves dry up in fall. You
can consider them to have a null vernalization gene, or inactive gene in
that location.

When we mix the winter dormancy genes ( aphaylla null vernalization ,
call it Va) with regular vernalization gene (then there is no
requirement for vernalization. And in many cases the photo-period
dormancy gene is inactive, as it would appear to be a recessive gene.
Thus the plant does not need vernalization. This gives the fall cyclic
rebloom as it doesnbt need vernalization, and winter dormancy genes are
not in a recessive set.

So cascading dominance of vernalization alleles is Va > Vf > vo. If
plant has an Va gene, it has fall cyclic trigger. If it has a Vf , then
it is a warm climate (ie California) rebloomer. If it has only vo, then
it needs vernalization before it can bloom.

The summer rebloomers turn out to initiate bloom as soon as they have
bud set ( maturity, plus temperature signal). This is a result of some
sort of defective gene, or more likely two defective gene. Both have to
be in four copies in order to have the summer rebloom.

I. suaveolens var. mellita may very well be a photo-period triggered
dormant plant, like aphylla.

Once a plant has the potential to rebloom, then all of the secondary
factors come into play. These involve plant growth rate, maturity level,
as measured by mature leaf count, and ability to utilize energy from
itbs environment. These all seem to be multi-factor genetic situations.
That is several genes are involved in each of them, with a cumulative
effect. But wilh all these factors, there wonbt be rebloom unless the
genes controlling bloom triggers are in place.

Chuck Chapman


-----Original Message-----
From: Linda Mann <lmann@lock-net.com>
To: iris <iris@hort.net>
Sent: Fri, Feb 3, 2012 8:36 am
Subject: [iris] REB: genetics, origins


I think there have been discussions here in the past about the
probable/possible origins of rebloom in TBs, but I've forgotten and was
wondering if there is an article somewhere that details their history?
Maybe in the Reblooming Iris Society Recorder, or one of the other
AIS/affiliate pubs?

I haven't looked yet, & am not really sure how to narrow down a search
of the archives for the info.

Especially wondering about theories of where the rebloom genes came from
that Smith and G.P. Brown were working with? Esp. the heat tolerant
'summer' blooming 'cold climate' rebloomers.

Tom Silver's reblooming CRICKET SONG, from I. cengialtii , I. variegata
(Beardsley clone),& I. suaveolens var. mellita, has gotten me wondering
about it again. Wondering if these rebloom genes are the same as those
in IMM, VIOLET MIRACLE, or another suite.

Linda Mann east TN USA zone 7b


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