REPLY: [pbs] permanent clones??
Lee Poulsen (Wed, 07 Jul 2004 11:30:14 PDT)

I know that at the US Dept. of Agric./Univ. of Calif. Riverside citrus
research center they have perfected the technique they use to obtain
virus-free versions of various citrus cultivars. They actually graft
and grow the virused cultivar in pots in a large room that is an oven
where they raise the temperature to a certain point and keep it there
continuously (somewhere between 100 and 120 deg. F. but I can't
remember exactly what). Then when new growth appears, they take just
the growing tip and tissue culture from that.

They discovered that above a certain temperature, viruses are unable to
migrate into the newly grown cells. Thus they are able to clone
completely virus-free plants. I've read that this method was used to
clean up the 'Meyer' lemon variety some years ago.

I don't know if this technique would work for lilies or other geophytes
as well.

--Lee Poulsen
Pasadena area, California, USDA Zone 9-10

On Jul 7, 2004, at 9:37 AM, John Bryan wrote:

Thanks for your message. Rather than an inner scale, I think the very
tip of the growing point is better in order to obtain virus free cells.
Hopefully they are taken before the virus can get to them, this would
be
even more the case if the tissue was taken from a plant that was
growing
rapidly, i.e. with added warmth to stimulate fast growth.

DaveKarn@aol.com wrote:

Judith Freeman (of Columbia-Platte Lilies and The Lily Garden) has
said the
issue is that meristem culture did not remove all the virus particles
in the
bulbs multiplied by meristem culture. The remaining few particles
were too few
to be detected by ELISA tests. For that reason, it is necessary to
periodically repeat these tests to have any assurance of virus
freedom. What, in
effect, is happening with these supposedly virus-free lilies is that
the
undetectable virus gradually works itself back up to levels that
present the standard
symptomology. I would imagine to get a truly virus free lily, one
would have to
continuously to incubate sections of the innermost scales.