While the individual genes may live on, unique gene combinations are lost with every successive 1:1 or low N population breeding scheme.
The only real preservation strategy, and responsible step (in the sense of preservation) is to open pollinate as many individuals from the original population as possible.
From there selections can be made and used for any other type of breeding scheme be it hybridization or within-line breeding, but the original pool, and all the alleles available in the initial population are still available for further selection in the future.
Most of the original unique populations (landraces or ancestral cultivars) have unfortunately been extremely bottle-necked and many valuable alleles have been eliminated, because the early breeders who worked with the species didn' realize that cannabis is an outcrosser and has different breeding requirements than most flower species.