North American Fruit Explorers mailing list at ibiblio

["Erwin Meekers" <erwin.meekers@luc.ac.be>]

Hi Dean,

I noticed that you are growing them under grow lights. My first thought
would be that the leaves are turning black because they get too much light
intensity (really "burning"). Have you checked the light intensity by
growing anything else under it? Perhaps some quick germinating and growing
vegetable seeds.

I've seen similar problems with my pear seedlings sown in spring 2003. Those
crosses were interspecific pyrus crosses : pear x nashi. All crosses grew
without any lethal symptoms, except for one cross (being Colette x Hosui).
Only 20% of this particular cross survived (with similar symptoms as you
described). As all seedlings of all crosses were grown under the same
circumstances I suspected it to be some post-zygotic breeding barrier.

Seedling lethality is not that uncommon. For instance 25% of Jonathan x
Golden Delicious seedlings will die from "pale green lethal". Both apples,
Jonathan and Golden Delicious, are carriers of the responsible gene. When
you combine such parents then 1 on 4 will get a "double dose" of this gene
(will be homozygous for that gene) and die shortly after germination.

Erwin Meekers

----- Original Message ----- 
From: "Dean Kreutzer" <deankreutzer@hotmail.com>
To: <nafex@lists.ibiblio.org>
Sent: Sunday, February 29, 2004 4:50 PM
Subject: [NAFEX] Pear seedling problems


> Hello all,
>
> I made some pear crosses last year and I am currently growing the
seedlings
> under grow lights.  Most of the seedlings are beginning to suffer;
symptoms
> are as follows:  The leaves starting from the tip are turning black, and
> eventually moves back to cover the entire leaf.  In others, the stem turns
> black and in time evelopes the seedling.  I have been removing all dead
> seedlings and cutting off blackend leaf material.  Does anyone have an
idea
> what this problem is and how to prevent it?
>
> Thanks for your help,
>
> Dean Kreutzer
> Regina, Saskatchewan Canada
> USDA zone 3