Core collections: a practical approach to genetic resources management

Large numbers of entries are now lodged in many of the world's germ-plasm collections of crop and pasture plants. This abundance of material, assembled to guard against its irretrievable loss, has intensified the problems of how best to conserve it and how to use it in plant breeding. Core collections have a major role to play in solving these problems. The core is composed of about 10% of the total collection, chosen to represent as much as possible of the diversity in the collection. The selection of the core entries should use the available data on the geographic origin, the genetic characteristics, and the possible value to breeders and other users of each accession in the collection. Stratified sampling from groups of accessions, in logarithmic or absolute proportion to the group size, is the best strategy. The core entries should be kept separately and not in one bulk population. The composition of the core should be adjusted as new material is included, or better data are obtained. The remaining accessions in the collection form the reserve, which should be conserved as secondary sources.Key words: germ-plasm collections, sampling strategies, Glycine tomentella, Hordeum vulgare.