REPLY: [pbs] permanent clones??

Lee Poulsen wlp@Radar-Sci.Jpl.Nasa.Gov
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.
> 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.

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