The genome of peanut sequenced with unprecedented accuracy

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Improved pest resistance and drought are among the potential benefits of an international effort in which scientists from the Agricultural Research Service (ARS) and their collaborators have drawn the clearest picture of the complex genomic history of cultivated groundnuts.

Scientists have embarked on this vast project to better understand the molecular and cellular mechanisms underlying peanut growth and development, as well as the expression of desirable traits, such as high seed yields, the 39 oil quality improvement and resistance to expensive diseases and pests, such as nematode roots.

Groundnut, Arachis hypogaea, is a major pulse crop of pulses and oilseeds, with a total global production area of ​​approximately 59 million acres. Besides oil, the peanut seed contains proteins, vitamins and other nutrients. US peanut production, valued at $ 2 billion a year, stretches from Virginia to Florida to Florida and from New Mexico to the west.

The history of cultivated peanut begins thousands of years ago in South America, where the genomes of two wild ancestors, A. duranensis and A. ipaensis, fused into a rare genetic event. The result, in modern peanuts, is a complex genomic mixture almost as big as the human genome, which accounts for about 3 billion base pairs of DNA.

Initially, scientists sequenced the genomes of the two wild ancestors separately, using DNA from both species rather than cultivated peanuts. This facilitated the identification of the structural features of the genomes and genes that reside there. The team reported this progress in a 2016 issue of the newspaper Genetic nature. Using state-of-the-art DNA sequencing devices, the researchers then sequenced the two merged genomes into a single commercial crop peanut, "Tifrunner", which bridged gaps in knowledge. missing.

This latest advance, reported in the May issue of Genetic nature, has already generated some interesting leads, including the geographical origin of A. duranensis, one of the two "parents" of the groundnuts grown. The genomic analysis conducted by the team on plant populations of wild peanut species revealed a region in northern Argentina called Rio Seco. Researchers suspect former emigrants from Bolivia have emigrated A. duranensis plants to another species they had brought with them –A. ipaensis, considered the other parent of peanut grown.

The researchers also reconstructed this genomic fusion by crossing the two old peanut species and analyzing the results obtained over seven generations of offspring plants. This has revealed an interesting pattern of DNA exchange and deletion (eliminations) in offspring plants, which probably explains the diversity of size, shape, color and other characteristics of the seeds present in the offspring. commercial peanuts. DNA exchange is unusual in that it occurs between the two "subgenomes" of the two contributing wildlife species, which is possible because of their great similarity.

Led by David Bertioli, a researcher at the University of Georgia, this effort is part of the continuity of the International Groundnut Genome Initiative and involves scientists from four ARS laboratories and other partner organizations in the United States, Argentina, Brazil, China and India.