HYB: Pod Sterility/ & Variable Fertility

From: Sharon McAllister <73372.1745@compuserve.com>

Obviously, I've fallen behind in even reading Iris Talk posts....

Celia wrote:

>  This is a basic question, perhaps too basic to be answered here. Perhaps
I
>  should go get a botany text. But can anyone tell me in layman's terms
why
>  -- why -- sometimes a plant is pod-sterile even though its pollen is
>  fertile?

The botany book is a good idea, not because the question is too basic but
because it's too complex.  Pod sterility does appear to be inheritable.  In
practical terms, this just means that hybridizers learn which plants not to
waste pollen on.  Personally, if I have two otherwise equal candidates for
parenthood I choose the one that's fully fertile  over one that's only pod
or pollen fertile.

>  Just so you'll know I'm not totally lazy, I searched the archives for
"pod
>  AND sterile" and came up with 23 postings, none of which explain why it
>  happens. Rick Tasco suggested that most irises are pod fertile and that
pod
>  sterility is rare. Someone else suggested sterility may come and go from
>  year to year. Another fellow quoted someone else who said there are no
>  infertile irises, only irises who haven't found the right partners. (I
>  think that last was a joke.)

I must agree with Rick, overall, although in the early world of arilbreds
pod sterility was a major problem.  A long story I think it's best to skip
for now.....

The second suggestion is also correct because fertility/sterility is not an
all-or-none proposition.  A certain potential exists, but its expression
can be significantly affected by environmental conditions.  That's why the
same plant may produce seeds one year, but not the next.

The last quote may have been offered in jest, but I recognize the saying as
a lesson I learned from Gene Hunt and have shared with many others.  It
just means that if you're in search of breakthroughs you keep testing and
examining the possibilities -- never, NEVER give up. 

IB-MAC, for example was presumed sterile for decades after its
introduction.  It was a genetic breakthough, essentially incompatible with
others of its time.  When it was crossed with WILLIAM MOHR, it produced
CAPITOLA through the miracle of gametic doubling.  Circumstantial evidence
suggests it played a role in C.G. White's breakthrough to fully fertile
arilbreds.  Once the amplidiploidlike hybrids became available, IB-MAC was
widely used as a parent.  Even got the reputation that it could "set pods
on anything except a fence post".  Slightly overstated, I admit, but it
certainly conveys the excitement felt by hybridizers of the time.

Then Sterling added:

>  I think I may have been the one that suggested iris fertility (pod and 
>  pollen) varies from year to year. I posed a question to the list as to 
>  why I thought I observed varied fertility but got no answers. 

<examples respectfully snipped>

My work has been with arils and arilbreds, much more than with medians and
TBs, so I was hoping someone with the appropriate experience would tackle
this question.

>  Does anyone have any ideas why fertility varies like this? Not that it's

>  important, I was just curious. I think it may have something to do with 
>  weather but have no proof.

In my experience, weather is crucial.  A late frost or dry spring can
interfere with pollen development.  A hot spring affects pod formation. 
Getting a pod on a TB -- ANY TB -- is always a major accomplishment.

Sharon McAllister
73372.1745@compuserve.com

------------------------------------------------------------------------
To unsubscribe from this mailing list, or to change your subscription
to digest, go to the ONElist web site, at http://www.onelist.com and
select the User Center link from the menu bar on the left.
Other Mailing lists | Author Index | Date Index | Subject Index | Thread Index