Status of the Arachis Germplasm Collection in the United States

Abstract

An extensive working collection of Arachis germplasm is maintained by the USDA at the Southern Regional Plant Introduction Sta. in Griffin, GA. Much of this collection is maintained also under long-term seed storage at the Nat. Seed Storage Lab. in Ft. Collins, CO. The working collection consists of 9027 accessions of A. hypogaea and 684 accessions of Arachis species. About half of the A. hypogaea accessions are unimproved landraces collected in the crop's centers of diversity in South America. The other half is comprised of germplasm obtained from countries outside of South America. The U.S. germplasm collection of peanut was the first major germplasm collection to have a working core collection. Research has verified that this core collection can be used to improve the efficiency of germplasm utilization. This has stimulated a great amount of germplasm evaluation work and has resulted in the identification of numerous sources of resistance to several economically significant pathogens. Considerable efforts in the U.S. also have been devoted to the use of wild species of Arachis for sources of resistance to pathogens. Programs are ongoing to introgress high levels of resistance or immunity to early (Cercospora arachidicola Hori) and late (Cercosporidium personatum Berk. & M.A. Curtis) leaf spots, nematodes, and viruses. Genetic resources have been particularly useful in adding disease resistance to peanut cultivars. This has had a significant economic impact on U.S. peanut farmers. The largest impacts have been from the development of cultivars with resistance to Sclerotinia blight (Sclerotinia minor Jagger), the peanut root-knot nematode [Meloidogyne arenaria (Neal) Chitwood race 1], and tomato spotted wilt Tospovirus. Use of these resistant cultivars has an estimated economic impact of more that $200 million annually for U.S. peanut producers.

Reaction of the Core Collection of Peanut Germplasm to Sclerotinia Blight and Pepper Spot1

“…Because of the large number of accessions in this and other germplasm collections, a core collection approach to increasing the efficiency of collection evaluation and trait utilization was proposed (12). The core collection approach to germplasm evaluation is a two-stage process that first involves screening a reduced number of accessions and using this information to identify clusters of accessions in the entire collection with increased probability of identifying the desired characteristic (16). The USDA collection of A. hypogea germplasm was the first to have a working core collection.…”

“…The USDA collection of peanut (Arachis hypogea) germplasm is comprised of over 9,000 accessions (16). Because of the large number of accessions in this and other germplasm collections, a core collection approach to increasing the efficiency of collection evaluation and trait utilization was proposed (12).…”

“…The core collection is comprised of 831 entries selected at random (1%), at random by country of origin (26%), and by multivariate clustering of phenotypic descriptor information (73%) to minimize repetitiveness in the collection while representing the collection's genetic diversity (16,18). The peanut core collection has been previously evaluated for resistance to tomato spotted wilt virus (TSWV), Rhizoctonia limb rot, late leaf spot, peanut root knot nematode, preharvest aflatoxin contamination, early leaf spot, and Cylindrocladium black rot (2,13,16,17,19). To our knowledge, the core collection has not been previously evaluated for reaction to Sclerotinia blight.…”

Impact of Drought Stress on Peanut (Arachis hypogaea L.) Productivity and Food Safety

“…The application of this physiological model in peanut-breeding programs has not been possible because of practical difficulties associated with measurement of the traits under field conditions. The USDA germplasm collection numbers over 9000 accessions of A. hypogaea (Holbrook, 2001) and about 800 accessions of Arachis species. Large Arachis species collections are also maintained at Texas A&M University and N. C. State University.…”

Screening of Virginia-Type Peanut Breeding Lines for Resistance to Cylindrocladium Black Rot and Sclerotinia Blight in the Greenhouse

“…Since then, numerous germplasm accessions among cultivated peanuts have been identified as sources of disease resistance (Holbrook and Dong, 2005;USDA, 2007). Additional resistant germplasm has also been identified among wild species collections (Stalker and Simpson, 1995;Holbrook, 2001).…”