at the laboratory, however, backups of clonal collections are limited to the same sites where the active collections are maintained. Many clonal crops can be conserved as seed, but they are impossible to maintain true to type by raising plants from seed. Many clonally propagated species take a long time to mature, and they are best preserved as mature live plants for plant breeding and research.

Clonal collections are expensive to establish, and they have many of the same problems that confront seed collections. Accessions must be maintained as plants in the field, which can require large tracts of land, or in screenhouses or greenhouses. Accessions may also be maintained as live sticks of budwood held under refrigeration or as tissue cultures. There may be losses during maintenance from insects and disease, freezing temperatures, electric power failures, or grazing animals. Clonal preservation is more expensive and labor intensive than seed storage. Clonal collections have been threatened as facility or land-use priorities have changed, as the principal scientists retired, died, or moved, or as funding declined. By establishing the national clonal germplasm repositories, a mechanism for stable, long-term maintenance for many important clonally propagated species has been provided.

The Interregional Research Project-1 (IR-1), located in Sturgeon Bay, Wisconsin, began in 1947 and is supported cooperatively by USDA through CSRS and ARS, and by the Wisconsin State Agriculture Experiment Station. It is the national repository for potato germplasm. The station has a collection of about 3,500 accessions of more than 100 wild and Cultivated potato species and is an important global resource.

IR-1 uses a variety of methods to maintain germplasm. True seed of potatoes, in vitro plantlets of selected clones, and tubers are maintained. The germplasm is propagated both for maintenance and distribution.

The National Small Grains Collection (NSGC) (Table 2-3) began in 1894 as a breeder's collection and is today the most widely used active collection in the NPGS (White et al., 1989). This collection, relocated in 1989 from Beltsville, Maryland, to Aberdeen, Idaho, holds more than 110,000 accessions of wheat, barley, oats, rice, rye, the wheat wild relative Aegilops, and the intergeneric wheat-rye hybrid, triticale. It is one of the world's largest collections with some of its accessions originating from nineteenth century plant explorations. About 100,000

Front Matter (R1-R16)

Executive Summary (1-20)

1 Managing Crop Genetic Resources (21-42)

2 Elements of the National Plant Germplasm System (43-86)

3 Administration of the National System (87-106)

4 Prescription for Effectiveness (107-144)

References (145-148)

Glossary (149-153)

Abbreviations (154-155)

Authors (156-160)

Index (161-173)