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Re: Survivors and hybridizers

  • Subject: Re: [iris-photos] Survivors and hybridizers
  • From: Robt R Pries rpries@sbcglobal.net
  • Date: Tue, 27 Jan 2004 12:36:03 -0800 (PST)

It is not impossible only because we have not even defined the problem. There are a multiplicity of problems that have not been answered in order to create a satisfactory experiment.

First we do not know that there are any cultivars or species for that matter that have a resistance. If we could identify plants that were resistant then we could organize a breeding program that would favor this resistance and even increase it.

Part of the problem is that all cultivars seem to have some minimal resistance and most will not succumb to rot just because of exposure. Even if you smeared rot infested tissue on to a healthy rhizome there is no guarantee that the plants resistance would be the factor in determining whether I became infected. Environmental conditions must be such that the rot can exist and cause problems. It is very difficult to isolate these two factors. 1. whether there is some genetic resistance and 2.whether the environment is controlled adequately to recognize this existence. It is a very important topic but no one has adequately defined the parameters to even begin an objective measure of the present situation. I suspect that there are some species and some varieties that may have traits useful in the defense of soft rot. But frankly I do not believe we know which species or cultivars carry these traits and how they might work. Incidental occurrences of soft rot are not adequate proof that unaffected plants are really resistant. In theory and probably in truth, there may be several approaches that plants have to defend themselves against this problem. It is possible that two of these approaches may or may not be additive. In other words there may be two or more defenses but it is possible that they may work against each other. It is likely that in the future when we know how DNA groups work to produce RNA proteins and the function of these, we might be able to sort this out. But for now we don?t really know enough to make great judgements.  Although I would encourage you to try, even if successful you will not really know of your success for many years. There will always be situations where relatively resistant plants will still be overcome by the microhabitat and the vagaries of the season. In essence, some people who rely on scant experience will still accuse you of having disease prone plants even if yours are much better than every one else?s just because they are not seeing an adequate sample.



Hensler <hensler@povn.net> wrote:
Are you saying that it's impossible to select for TBs that show a resistance
to rot?

I'm curious about this since it is one of the things I've been selecting
for. The other major fault is susceptibility to leaf spot.

Christy

Skip & Christy Hensler
THE ROCK GARDEN
Newport, WA
http://www.povn.com/rock/
----- Original Message -----
From: "Robt R Pries" <rpries@sbcglobal.net>

> Let me point out that I don't believe any hybridizer has ever selected for
rot resistance. To do so you would have to deliberately infect your plants
and see how they respond. Everyone that has grown TBs for many years has had
a season or more in which the plants might be devastated by soft rot.  Even
under that type of condition the survivors tell you very little about their
resistance. You would have to rule out microclimates and many other factors.
In my opinion Iris people have not assembled any information that can say
anything at all about rot resistance. Good scientific investigations have
not been done that give us this information.
>





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