DUPLICATION WITHIN AND BETWEEN GERMPLASM COLLECTIONS .1. IDENTIFYING DUPLICATION ON THE BASIS OF PASSPORT DATA

Principles of duplication within and between genebank collections have been explored, terminology is proposed and the difficulties in identi fying probable duplication are discussed. Identical duplication concer ns genetically identical accessions, whereas common duplication refers to accessions derived from the same original population that are mixt ures of lines with differing genotype frequencies, or random mating po pulations with the same alleles but differing allele frequencies. Part ial and compound duplication are types of incomplete duplication. An a dditional type of duplication is the relation between the parents in a cross and their offspring, i.e. parental duplication. Identifying pro bable duplication on the basis of passport data is often hindered by t heir incompleteness or poor quality. The genetic identity of accession s is also subject to changes during maintenance in genebanks. Therefor e, probable duplicates will often not be true duplicates. Examples fro m the European Barley Database illustrate the problems.