Dear Rodger: Clonal selections of Lilium, did recover vigor and lost the virus problem when raised from tissue culture, however in a few years they again lost vigor. Another batch raised from tissue culture lasted for an even shorter period of time. The regained vigor is not permanent even though virus free. Certain genera it seems just get weaker with the passage of time. Cheers, John E. Bryan Rodger Whit lock wrote: > > On 6 Jul 04 at 9:35, zonneveld wrote: > > > ...most clones of vegetatively propagated plants have to be > > replaced by new ones due to loss of vigour. > > But isn't that loss of vigor usually due to the slow buildup of the > viral titer? > > I am aware of a number of old clonal cultivars that were very weak > and very tricky to keep going but which recovered vigor when put > through tissue culture to eradicate viruses. > > -- > Rodger Whitlock > Victoria, British Columbia, Canada > "To co-work is human, > to cow-ork, bovine." > _______________________________________________ > pbs mailing list > pbs@lists.ibiblio.org > http://www.pacificbulbsociety.org/list.php