Exploratory sequencing of wild and cultivated peanut (Arachis ssp.) genomes

Cultivated peanut (Arachis hypogaea L.) is a Papilionoid grain legume crop. It is an allotetraploid of recent origin with an AB type genome (2n = 4x = 40) and has very low DNA polymorphism, a characteristic that has hampered genetic studies. The A and B genomes are of similar size and are composed mostly of metacentric chromosomes. The genome of peanut is estimated at about 2.8 Gb and with a high repetitive DNA content. It’s most probable diploid ancestors are A. duranensis Krapov. & W.C. Greg and A. ipaënsis Krapov. & W.C. Greg, donors of the A and B genomes respectively. These two sub-genomes diverged from a common ancestor about 3-3.5 million years ago. Genetically, the two sub-genomes have very high genetic synteny, and do not appear to have undergone major structural rearrangements after polyploidization. In contrast the repetitive DNA components of the sub-genomes are very significantly diverged. This study aims to characterise the A and B genomes to determine their sequence similarity in conserved homologous regions and the general characteristics of their repetitive DNA contents.