Re: CULT, HYB: 450 Known Rotters

Let us not get panicky.

While Don may be right that rot resistance is a genetic trait, I am 
sure, as he is a good biologist, he did not mean to say that genetics 
are the be-all and end-all of rot susceptibility.

Any iris will rot under conditions that strongly favor rot.

I think it would be more accurate to say that rot resistance is 
PARTLY genetic and partly dependent on the environment in which the 
variety finds itself.

One would be hard put to find any commercial tall bearded iris that 
ALWAYS rots.  Such a variety would not last long in trade unless it 
had other desirable qualities that would justify the struggle to keep 
it alive.

Hybridizers, I am sure, do not knowingly introduce varieties that are 
unusually susceptible to rhizome rot UNDER THEIR CONDITIONS. However, 
when that variety is grown somewhere else, it might be a different 
story.  Since almost nobody tests their plants pre-introduction all 
over the country or the world, naturally you might get a plant that, 
under your conditions, is going to rot more than usual.

Also, keep in mind that we are not at all helpless in the face of 
rhizome rot.  There are many things that can be done to save plants 
attacked by rot--it is not an all-or-nothing proposition.  Last 
spring and summer I struggled mightily with rhizome rot (Erwinia 
carotovora) on almost all the bearded irises I grow.  This spring, 
not a single case so far, and these are the same plants.  The 
difference is that this spring I did not fertilize before bloom and 
we are, of course, having much drier conditions.  I also made sure to 
catch leaf spot before it got started.  Proper culture minimizes the 
chances of rot for any iris.

So--Don might have 450 varieties that sometimes get rot, but 
sometimes they don't, and for many of them, I'll bet that the rot is 
a minor problem easily cleaned up by the usual methods.  He continues 
to grow these plants despite the problems because they have other 
qualities that overcome their possible tendencies to decay. Likewise, 
the plants that never rot in Don's garden might well be problematical 
somewhere else.

Breeding for rot resistance has not been a priority with hybridizers 
because they are focused on the plants themselves, their blooms, 
quality of stalk and foliage, and perhaps even season of bloom.  To 
insist that absolute rot resistance under all conditions be added to 
these qualities is to look for pie in the sky.  Everything in life is 
a compromise--we want to grow beautiful irises, and sometimes the 
cost is extra vigilance in culture.

-- 

Bill Shear
Department of Biology
Hampden-Sydney College
Hampden-Sydney VA 23943
(804)223-6172
FAX (804)223-6374
email<wshear@email.hsc.edu>
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