A CORE COLLECTION FOR THE UNITED-STATES ANNUAL MEDICAGO GERMPLASM COLLECTION

The United States National Plant Germplasm System contains 3159 access ions from 36 species of annual Medicago. Although there is increasing interest in the annual medics for use in sustainable agriculture, the U.S. collection is under utilized because of lack of agronomic informa tion. Development of a core collection could facilitate easier access to the germplasm collection and enhance its use. The core collection s hould consist of a sample of accessions that represents the range of v ariability within the germplasm collection with minimum redundancies. To select a core collection of annual Medicago species, a subset of 12 40 accessions was evaluated during the summer of 1990 for 16 agronomic and morphological traits. Accessions within species were grouped by c luster analysis utilizing an unweighted pair group method with arithme tic averages. Intraspecific phenotypic diversity determined the number of accessions for that species selected for the core collection. One accession per cluster was selected for each species for the core colle ction. Accessions were chosen within a species to represent the greate st diversity in geographical regions. The selected core collection of 211 accessions was reevaluated during the summer of 1991. The core col lection was found to represent the variability of the germplasm collec tion and to remain stable between the two evaluation years. This study can be used as a model method for selecting a core collection for mul tispecies germplasm collections.