Re: Survivors and hybridizers

You know this is a good discussion thread, but is is more appropriate 
on iris talk (iris@hort.net).

Iris photos is specifically designated for the exchange and discussion 
of iris photographs and associated topics (e.g., pictures of rot...)

John


On Jan 27, 2004, at 12:36 PM, Robt R Pries wrote:

> 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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John                | "There be dragons here"
                          |  Annotation used by ancient cartographers
                          |  to indicate the edge of the known world.

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