Due to the size of, and lack of proper information about many germplasm collections, choosing material is not always easy. Core collections aim at presenting the user with a subset of material that contains as much diversity as possible, given the requirements for this set.
A germplasm collection is usually the result of historical events and arbitrary decisions; collecting missions and specific research programs often result in over representation of certain material whereas other types of material can be underrepresented. Core collections try to increase the balance between the types of material in a relatively small selection of accessions.
The size of a germplasm collection can limit its accessibility, and thus hinder its utilisation and management.