RE: CULT: evaluating disease resistance

Hi,
I have been taking many pictures at the
conventions.  This years CD will have over 1000
pictures but only a few clumps.  I will make sure
that I get a good many pictures of clumps in
Portland.  Will you be there?
Char, New Berlin, WI

-----Original Message-----
From: owner-iris@hort.net
[o*@hort.net] On Behalf Of Linda
Mann
Sent: Thursday, September 08, 2005 6:54 AM
To: iris- talk
Subject: [iris] CULT: evaluating disease
resistance


I've posted a series of photos of irises with
various sensitivity to disease here.  I believe
this is soft rot, but have heard others describe
this appearance as due to other causes.
Regardless of cause, I am trying to develop
seedlings that are resistant to it.

In my experience, cultivars exhibiting reddish
brown shriveling of leaf tips eventually will
succumb to rot here.  This does <not> look the
same as browning of leaf tips due to drought or
sudden freeze, which usually affects <all> leaf
blades in the fan the same way.

Cultivars and seedlings that have this kind of
damage may survive and bloom here if the weather
is just right.  They may even thrive for a time,
but when the weather doesn't suit them (i.e., hot,
humid, and several inches of rain every few days),
will develop rot in the base of the fan.  If
untreated, the rhizome will often. Sometimes they
grow fast enough that increases will live to bloom
another day.  Sometimes the plant is lost.

The sickly things in the photos are my seedlings -
no hybridizers outside my own garden created these
gems :-(

Those reddish brown, shriveled leaves are what I
look for (to avoid) when I am looking at cultivars
growing in other people's gardens.

But when I went to take photos of examples, I
discovered that the <majority> of cultivars had
some extent of this kind of foliage, thanks to the
constant rain and heat this summer.  I realized
that when I am evaluating foliage, I am
subconsciously comparing it to foliage on other
cultivars in the same growing conditions, using
some cultivar I know as a reference point.

In the examples I posted, ICE CREAM SOCIAL and my
"super tough" seedling each has up to 9 leaf
blades per fan that are unaffected by disease.
Nice & green.  I found this to be true of all
cultivars that I consider supertough here.  At
most, only one leaf blade on each side of the fan
was affected.

On the unhealthy ones, there were as few as 2 or 3
leaf blades that had no indication of damage.
Some had as many as 3 leaf blades on <both> sides
of the fan affected and the green blades were
'wet' looking.

One of my favorite "reference plants" is
IMMORTALITY.  Comparing its foliage to that of
seedlings lets me know that most of those puny
plants I photographed will not live to blooming
size.  Or more likely will bloom, but will rot
immediately afterwards.

This is what I'm actually wishing I could see in
convention photos.  If each display garden had
IMMORTALITY growing in it for comparison, and if
plants were <not> groomed, photos of foliage (with
IMM foliage as a
"control") would help me tremendously in finding
new cultivars to try here.

Even if flower beds were groomed, the relative
number of green leaf blades would probably provide
enough idea of health for my needs.

Thanks to Betty for pinning me down on exactly
what it is I'm looking for.

--
Linda Mann east Tennessee USA zone 7/8
East Tennessee Iris Society
<http://www.korrnet.org/etis> American Iris
Society web site <http://www.irises.org> talk
archives: <http://www.hort.net/lists/iris-talk/>
photos archives:
<http://www.hort.net/lists/iris-photos/>
online R&I <http://www.irisregister.com>

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