Status of the U

Status of the U.S. Medicago Germplasm Collection.

Stephanie L. Greene and G.R. Bauchan

USDA-ARS, Prosser, WA, and Beltsville, MD, USA

The United States Department of Agriculture began acquiring Medicago germplasm in 1898. Cultivars, landraces and wild species were collected directly in the field by plant explorers and scientists or obtained from agricultural institutes, seed companies and U.S. Embassies from around the world. In the last 100 years, more than 60 collection trips have focused on alfalfa. The majority of accessions that are available today were received after the 1940s, when preservation efforts were first initiated. During the 1950s, 60s and 70s the collection grew by an average of 1400 accessions per year. During the eighties, more than 4200 accessions were added. During the nineties, the collection grew by 1400 accessions.Ê The collection currently contains over 7000 accessions representing 76 species from 94 countries. Efforts in the last two decades have focused on maintaining accessions, evaluation and enhancing the use of the collection.Ê Original seed (or best seed lot) has been increased using cages to prevent cross contamination. This has been completed except for accessions that require special care due to limited quantities and/or poor quality seed, or special growth conditions (i.e. wild species). Although about 500 accessions fall under this category, facilities and funding are insufficient to address this issue. The historic passport data in GRIN has been upgraded (Greene 1998). An important emphasis in the last two decades has been germplasm evaluation, directed by the Alfalfa Crop Germplasm Committee (CGC). By 1997, about a third of the perennial accessions had been evaluated for 58 descriptors, with a focus on Medicago sativa subsp. sativa. Two-thirds of the annual medic species have data that characterize production, phenology and growth (Johnson and Graves 1998). Other accomplishments have included the development of core subsets, one each for the perennial and annual Medicago species (Diwan et al. 1994, Basigalup et al., 1995) and Rhizobium. ÊThe Medicago collection is widely used. In the past decade, seed requests have supported applied research, crop breeding, basic research and new crop development (in that order). The CGC evaluation program was terminated in 1997 due to lack of funding. Despite this, use of the collection has continued to grow. For example, there has been recent interest in species related to alfalfa, and in M. truncatula. In addition to making diverse germplasm available for breeding and research, the NPGS Medicago collection is an important tool for conserving genetic diversity within the genus. The collection however, has significant gaps. There is a limited number of nondormant alfalfa, limited representation of the Medicago sativa complex, and secondary and tertiary alfalfa gene pool. The collection could play a stronger role in conserving obsolete US cultivars. Representation of M. ruthenica, M. arborea, M. marina and M. edgeworthii make a significant contribution to global conservation. However, Prosperi et al. (1996) determined 75 % of perennials species are ãendangered, endemic or rare; or have very few accessions available in gene banks.ä Although progress has been made in the last 30 years, advances need to continue to ensure the needs of collection users and conservation are met. The challenge will be to continue advancing despite insufficient resources.Ê

Reference

Basigalup, D.H., D.K. Barnes, R.E. Strucker. 1995. Development of a core collection for perennial Medicago plant introductions. Crop Science 35:1163-1168.

Diwan, N. Bauchan, G.R., and M. McIntosh. 1994. A core germplasm collection for the United States annual Medicago germplasm collection. Crop Science 34:279-285.

Greene, S.L. 1998. U.S. Medicago germplasm collection: Celebrating a century of plant collecting, introduction and conservation. pg. 41. Report of the 36^th NAAIC, August 2-6, Bozeman, MT.

Johnson, R.C. and W. Graves. 1998. Overview and agronomic evaluation of the USDA annual medic germplasm collection. Pg. 11. Report of the 36^th NAAIC, August 2-6, Bozeman, MT.