Callus culture is not a good way to do this, mainly because if you have some form of contamination, you've lost your lines. The solution would be to have multiple containers of each line, but even then there is the chance of loss- not to mention all the extra work it takes to go from singlet to triplicate (or more). All it takes is an infestation of mites, and you'll be autoclaving hundreds of containers with each daily rouge, as any lab or any reasonable size has experienced at least once. Maintenance over the course of years or decades becomes risky and expensive- a bad combination. Normally DMSO + cryogenic storage (liquid nitrogen) is the best answer, a trivial problem for any well-equipped tissue culture lab.
Even then, I remain unconvinced as to the use of "libraries." Marijuana growers, as a group, are very forward-thinking: who cares where we've been? If the old strains are so good, why aren't they more popular? Everyone wants the next best thing, not last weeks' hot topics. Go through any book on marijuana that's more than 5 years old, and try to find cuttings or seeds of any of the old favorites; you will find it difficult to locate the vast majority of these.
I don't know what you mean by cultured seeds. Do you mean embryo rescue, or perhaps artificial seeds?
