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Seed sterilization

Antonio R. Franco bf1rodri at cc.uco.es
Fri Jul 9 04:18:01 EST 1993

Here goes a copy of the microwave sterilization method I sent to Melissa
I feel curiosity in knowing if it works for somebody else. Please let me 
know about your bad or good experiences (if you try the method) by sending me
a message to BF1RODRI at CC.UCO.ES

Dear Melissa:
Now, I can help you a little bit, but only if you are working with small 
seeds (Arabidopsis, tobacco). This protocol does not work for big seeds like
soybean, etc.
First thing. You have to believe me. It works for me every time with total
success, and without any sort of problem.

Introduce a half-full glass with water in your microwave oven. This is to
protect your oven by absorving the excess of energy.
Put your seeds into a sterile plastic tube. For both, tobacco and 
Arabidopsis, I put around 50-100 seeds in each tube. I am talking of those
tubes having any kind of cap. Try to distribute all of the seeds thorough 
all the tube. Laid down your tube horizontally in the oven's plate. 
Turn on your microwave at MAXIMUM power for around 7-8 min (my oven has an 
output of 650-700 watts). Wait 1-2 min to let the tube cool down. Turn on
the oven another 7 min. Use your sterile seeds. DO not be afraid, use 
MAXIMUM power. Go for it!.

OLD FACTS: With both untreated or clorox-treated seeds, I always got some 
plants growing among my fungus jungle. Consider this as a bad joke. Obviously 
none of them survived after 1 week.

NEW FACTS: You got (sometimes) an curve platic tube (because of the heat) with
around 50 microwave-treated seeds. Percentage of germination: over 99 %. In the 
3-4 years I am doing this, I never have found clues indicating "bad" 
changes in my plants. All of them grown vigorously, and you know that the 
microwave energy is not powerfull enough to modify DNA, so you have not to 
expect mutants (maybe this has to be investigated further). I killed all and 
any of MY contaminating bacteria or fungus spores around. I think seeds survive
because their oil and water content is low, and this makes the seeds 
relatively transparent to the microwave energy.
Once upon a time, I had my twice microwave-treated seeds kept for 6 month 
in my refrigerator, and I had a doubt about if sterility was maintained 
after that period of time. So, I treated my seeds and, again, over 99 % of my 
seeds grown without any shadow of contamination (after 4 treatments!).

Obviously, I cannot guarantee this methods work with all kind of 
contamination, but I think it deserves a try.
If you try this method succesfully, let me know, as I will post this method
to the newsgroup. But I would like to get some positive feedback from 
people outside my laboratory before spreading the method, only to be sure.

Antonio R. Franco
Dpto Bioquimica y Biologia Molecular
Facultad de Ciencias
Uniersidad de Cordoba
E-14071 Cordoba

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