The genome of the peanut, a staple food for millions in the developing world as well as an important cash crop, has been sequenced by a multinational consortium including researchers at the UC Davis Genome Center.
The new peanut genome sequence will be available to researchers and plant breeders across the globe to aid in the breeding of more productive, more resilient peanut varieties. Sequence data will be online at peanutbase.org from April 2.
Peanut (Arachis hypogaea), also called groundnut, is an important crop both commercially and nutritionally. Globally, farmers tend about 24 million hectares of peanut each year, producing about 40 million metric tons. While the oil and protein rich legume is seen as a cash crop in the developed world, it remains an important sustenance crop in developing nations.
The peanut grown in fields today is the result of a natural cross between two wild species, Arachis duranensis and Arachis ipaensis, that occurred in the north of Argentina between 4,000 and 6,000 years ago. Because its ancestors were two different species, today’s peanut is a tetraploid, meaning the species carries two separate genomes which are designated A and B sub-genomes.
IPGI researchers sequenced the DNA of both ancestors, covering more than 96 percent of peanut genes. Professor Richard Michelmore’s laboratory at the UC Davis Genome Center generated ultra-high density genome maps for the two peanut genomes. These maps provided the frameworks for ordering the sequence fragments and joining them together into chromosome-scale pieces. UC Davis researchers also sequenced the genes that are actually expressed in each ancestor (the transcriptome).
By comparing the ancestral sequences with that of cultivated peanuts, geneticists and breeders will be able to look for genetic changes involved in domestication and make it easier to introduce traits from wild peanut that can improve crops such as disease resistance and drought tolerance, said UC Davis research scientist Lutz Froenicke.
The two ancestor species were collected from nature decades ago. One of the ancestral species, A. duranensis, is widespread but the other, A. ipaensis, has only ever been collected from one location, and indeed may now be extinct in the wild. Fortunately because of the long-sighted efforts of germplasm collection and preservation, both species were available for study and use by the IPGI.
About the peanut
In the U.S. peanuts are a major row crop throughout the South and Southeast. While they are an economic driver for the U.S. economy, the legume is also crucial to the diets and livelihood of millions of small farmers in Asia and Africa, many of whom are women. Apart from being a rich source of oil (44–55 percent), protein (20–50 percent) and carbohydrates (10–20 percent), peanut seeds are an important nutritional source for niacin, folate, calcium, phosphorus, magnesium, zinc, iron, riboflavin, thiamine and vitamin E.
About the International Peanut Genome Initiative
The International Peanut Genome Initiative brings together scientists from the United States, China, Brazil, India and Israel to delineate peanut genome sequences, characterize the genetic and phenotypic variation in cultivated and wild peanuts and develop genomic tools for peanut breeding. The initial sequencing was carried out by the BGI, Shenzen, China. Assembly was done at BGI; USDA-ARS, Ames, Iowa; and UC Davis. The project was made possible by funding provided by the peanut industry through the Peanut Foundation, by MARS Inc., and three Chinese Academies (Henan Academy of Agricultural Sciences, Chinese Academy of Agricultural Sciences, Shandong Academy of Agricultural Sciences). A complete list of the institutions involved with the project and the other funding sources is available at www.peanutbioscience.com.