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Withering of _in vitro_ plants

Sylvain Chamberland chambers at ERE.UMontreal.CA
Wed Mar 24 11:26:40 EST 1993

I'm working with transgenic potato plants; specifically I'm doing
studies on the promoter of a gene by inserting in potato, deletions of
the promoter linked to a reporter gene (well, I'm rather doing the analyses,
someone else did the transformations...). I discovered lately that a group of
clones from the same construct (a pBI101 construct, a modified Ti plasmid
from _Agrobacterium tumefaciens_) are withering.

We have of course to micropropagate the plants (_in vitro_) to conserve them.
They are potato plants (_Solanum tuberosum_) cv. Desiree which have been
transformed using _Agrobacterium tumefaciens_ some 2 to 3 years ago. Their
medium has been changed every other month ever since (a standard plant
culture medium with MS salts). They have been gradually withering for 4
months (what I mean is that with time, after each micropropagation, their
maximum height decreases and some leaves look somewhat yellow. And they
don't look too good. The smaller plants don't even have roots).

I noticed also that a lot of those _in vitro_ plants have black spots no
bigger than 1mm in diameter under the leaves, and sometimes on the stems
as well (but rarely); there can be 1 to a dozen of those spots on the leaves.
There is no contamination in the medium. But afterwards I noticed that a
lot of plants from other constructs have the same spots but appear
nevertheless to be in good health.

So I have the following questions:

Has anyone encountered similar spots under the leaves of _in vitro_ plants
from _Solanum tuberosum_, or other species?

If so, has anyone seen a correlation between those spots and the withering
of _in vitro_ plants?

Is there a limit to the time you can cultivate _in vitro_ plants by

Well I would appreciate any insight you could give me...  :)

Sylvain Chamberland      | INTERNET: chambers at ERE.UMontreal.CA
Departement de biochimie |-------------------------------------------
Universite de Montreal   | En Afrique, quand un vieillard meurt, c'est une
Montreal, Qc CANADA      | bibliotheque qui brule.     - Hampate Ba

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