PBF Project

Brad Kasperek wrote:

:  I hate to be a party "pooper", but I have to agree with Rick that the
:  corolation of PBF and hardiness is a non-starter. 

If it were a simple matter of cause-and-effect there would be no debate, no
reason to test the theory.  But we are faced with a situation in which some
people have strong anecdotal evidence to support one position while others have
equally strong evidence to support the opposite.  I suspect that both groups are
right and believe that a statistical analysis will help us get to the truth of
the matter.

This reminds me a bit of the long-term controversy over maternal inheritance,
where people who actually work with traits that are transmitted via the
extra-chromosomal DNA take it for granted and those without such experience
don't believe in it.  Both have valid observations.  Taken separately they
appear contradictory, but taken together they give us a better overall
understanding of iris genetics.

:  Some of the best PBF TBs
:  come out of California and they don't like to go dormant in the winter. The
:  Schreiners have worked for decades selecting breeding stock for winter
:  dormancy.  If the foliage dies back to the ground, and the iris comes back
:  with vigor the next spring, then you have dependable winter hardiness.

Under SOME conditions.  Here, summers are much more stressful for TBs than
winters.  The long-term survivors are those that can go green-dormant  in both
summer and winter.  The ones with foliage that dies back completely in
anticipation of a hard winter shorten their own growing season to the point that
they often fail to come out of hibernation.

:  I know someone is
:  thinking "what about genetic linkage" ( e.g. PBF and hardiness genetically
:  tied together)  I'm not a geneticist, but I think linkage is usually related
:  to recessive characteristics.

In the genetic sense, "linkage" refers to traits transmitted by genes that
reside on the same chromosome.  The strength of the linkage is related to the
distance between loci and thus the chance of separation by "crossing over".
(Aren't you glad I consider THAT beyond the scope of the current discussion?)
Linkage itself has nothing to do with whether a trait is dominant or recessive
-- but its usefullness has historically been in work with recessive
characteristics.

It is much too soon to attempt explanations as to why there IS or why there
CANNOT BE a relationship between PBF and long-term survival.   The immediate
question is merely whether there is a statistically significant relationship
with any of the factors that we can measure.    The time for debating the
relative merit of various explanatory physical mechanisms is AFTER we've
identified a relationship to be explained.

Sharon McAllister (73372.1745@compuserve.com)
aka "The Dragon Lady" to her students

 

There is PBF in many of the winter hardy species, I. variegata, I. aphylla,
and  I.croatica to name the ones I'm acquained with.   However, the
significant growing trait they all have is -Their foliage dies back.  I'm
going to do some hardiness crosses to these species and will select breeding
stock based on foliage "die back", not PBF.
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