microwave info

Luca Comai comai at U.WASHINGTON.EDU
Fri Aug 6 15:11:28 EST 1993

Dear Network,
I did not get an overwhelming response to my query on microwaving seed for
surface sterilization. Obviously, most people must be flipping burgers on a
barbecue at the beach rather than microwaving in the lab.
Here are the responses I got:

1. Richard Gardner, Auckland
"We tried it for 2 x 7 and killed the little xxxxers (edited for the network).
Dunno if they were properly dried tho."

2. June Medford, Penn-state
"I am concerned what the microwave technique could do to the young meristem
and/or forming leaf primordia. Because development is not OFF in the dry seed
but just arrested, some abnormalities could be introduced.  I wonder if any
folks have seen abnormal leaf primordia (esp. leaves 1 and 2).  The alterations
may be slight, but significant."

3. Steve Sinden, Missouri
"I microwave on full power for 10 minutes and I don't use H2O.  I microwave in a
small manila envelope set on top of one or two beakers to prevent burning. I
haven't had any problems with fungal contamination of seeds. So far the
microwave hasn't blown up and I haven't had significant loss of germination."  

4. Joshua Heazlewood, Latrobe
"Here are my results so far using the seven minute
high, two minute cool, seven minute high method, with only a beaker (250ml) of
water, (no chips?). Four GM plates with seven seeds per plate, sterized as above
in a 1.5ml
eppendorf gave 20 successfully germinated seeds from 28 (71%). No fungal
contamination as yet (21 days old).
	Eight Gm plates 7-8 seeds per plate, sterilized as above in a 15ml Falcon tube,
gave 40 successfully germinated seeds from 58 (69%). One plate with fungal
contamination (10 days old) Microwave output is 2450MHz, 500W., In my opinion
the method is much faster than the chlorine etc method, but am concerned with
the percentage of germinated seeds, approx 70%."

5. Beth Rosen. Michigan State
"I used three samples, one with two exposures of 7' each, one with 10', and one
with 13'. In all cases 1 to 5% of the seed became contaminated.I think that if
this requires more than 40'total (which it might because my microwave is only a
500W model) and if only one sample of seed can be sterilized at a time, it will
not save much time over traditional bleach sterilization where many samples of
seed can be processed simultaneously."

My take-home message is that, while this method can work, seed quality, oven
type, and sterilization set up can produce indesirable side effects, such as
seed death and partial sterilization. June suggested other possible
complications. I hope that we will hear more on this approach.
        By the way, for easy liquid sterilization of multiple samples we use a
home made apparatus that looks like a dot blotter with good results.

Ciao, Luca Comai


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