The CPC was fully converted to true seed populations in the 1960s, thus losing the identity of the native cultivars in the collection but conserving the alleles present in each accession in a form which is secure against the casual losses suffered by annually planted clones. Now, all accessions are regenerated as required by sowing sufficient seed to obtain 20 seedlings, and at flowering randomly intercrossing those seedlings by harvesting bulked pollen and reapplying to all open flowers. With the kind cooperation of the UK Potato Quarantine Unit, SASA, Edinburgh, we test every individual raised for quarantine organisms which could be present in stored seed, and return high grade tested true seed to our Working and Base collections for distribution and safekeeping for the future. Seed currently entering these collections should retain viability for around 100 years, and it is our aim to turn over the entire collection and test it to current quarantine standards every 25 years or so.
The annual rejuvenation cycle involves taking around 60 accessions through the following steps, though some of these accessions will need to be retained as clones for additional rejuvenation in subsequent years:
