plant extract as possible media pathogen risk

[Alan L Winthrop <TQPLlab@AWINTHROP.FREESERVE.CO.UK>]

Dear Group,

I have been puzzling over this question for a while and a recent posting
on another group has prompted me to seek some expertise, perhaps
from the virologists as well.

It has been common practice in plant tissue culture, especially orchid
aseptic seed raising to use plant extracts as complex additive
media supplements. The most common that springs to mind is banana
pulp, coconut water, potato tubers, or birch bark sap.

I am sure that infected plant material reaches our supermarkets. (This
is known in the UK in the case of imported tomatoes with seed born
exotic virus infections). Severe infections might be shop rejected due
to disfiguring but what about mild infections or asymptomatic infected
produce?

Please correct me if I am wrong....
If plant extracts have been prepared from virus infected plant material
it is theoretically possible that in its 'raw state' it poses a
subsequent plant pathogen risk, for example by hand infection?

More importantly does anyone know if infectivity remains after
autoclaving? In media preparation many labs work on the side of reducing
autoclave cycles to preserve media additives efficacy or pH and
I wonder if this possibly might not kill the virus infectivity?

When I used to work with virus infected plants we used to
use bleach or autoclave waste for 40 mins at 121C. and then
incinerate. This is clearly at odds with what one does in media
preparation.

Other proceedures such as media microwaving surely should not be
adopted when using plant additives.

Footnote...perhaps someone working with coconuts can advise if the
liquid endosperm is free of virus infection or have I got that wrong?

Have generations of orchidists and tissueculturalists been infecting
their cultures unknowingly?

Any advice or thoughts on this would be of interest to me.
Best regards
Alan L Winthrop
TQPL@TissueQuickPlantLabs.com
http://www.tissuequickplantlabs.com