Biology, speciation, and utilization of peanut species

Authors: STALKER, H - North Carolina State University; Tallury, Shyamalrau - Shyam; SEIJO, G - Universidad National Del Nordeste; LEAL-BERTIOLI, S - Embrapa

Submitted to: Peanuts: Genetics, Processing Utilization
Publication Type: Book / Chapter
Publication Acceptance Date: 6/2/2015
Publication Date: 1/4/2016
Citation: Stalker, H.T., Tallury, S.P., Seijo, G.R., Leal-Bertioli, S.C. 2016. Biology, speciation, and utilization of peanut species. In: Stalker, H.T., Wilson, R.F.(Eds), Peanuts: Genetics, Processing Utilization. Amsterdam, NX, Academic Press and AOCS Press, p.27-66.

Interpretive Summary: Peanut, also known as groundnut (Arachis hypogaea L.), is a native new world crop. Arachis species originated in South America and are found in tropical and subtropical areas. Species have evolved in highly diverse habitats and both annual and perennial types exist. It is likely that the genus originated in the highlands in the southwestern Mato Grosso do Sul region of Brazil and later spread into the drier lowlands of South America. Species in the genus Arachis are widely distributed in South America from Northeast Brazil to southern Uruguay and from the Andean lowlands in the west to the eastern Atlantic coast, and the distribution is continuous across this region. Species grow in deep friable sand to thick, gummy clay and on schist rocks with virtually no soil, suggesting that species have adapted to highly diverse and harsh environments. Fruiting below ground likely protected the seeds from predators and the many root adaptations (e.g., rhizomes, tuberous roots) likely helped species to adapt to new habitats. Conversely, the geocarpic fruit impeded rapid spread into new environments. The center of origin for the cultivated species A. hypogaea is believed to be southern Bolivia to northwestern Argentina based on the occurrence of the two progenitor species Arachis duranensis and Arachis ipaënsis, and archaeological evidence gathered in this region. Advances in the peanut genome sequence and the availability of new genomic tools will help clarify the origin and evolution of the cultivated and wild species of the genus Arachis. Wild peanut species were important as sources of food in pre-Columbian times and several taxa are still widely used as forages or for their aesthetic value as a ground cover, but only A. hypogaea is economically important today as a human food source. Importantly, many Arachis species have extremely high levels of disease and insect resistances that are not present in cultivated peanut.

Technical Abstract: The genus Arachis has a large number of highly diverse species. Large collections of cultivated peanut exist at multiple locations and several hundreds of wild species are maintained in germplasm banks. Many of the species have been characterized for agronomic traits, but much of the germplasm collection remains to be evaluated for disease and insect resistances. The incorporation of wild alleles into crops is a proven strategy to develop improved varieties with pest and disease resistance. However, the extent of utilization of the useful allele reservoir in wild species and its impact on peanut breeding has been relatively limited because of restrictions to crossability, multiplication rate, and, until recently, to the lack of appropriate molecular tools to analyze and follow traits in hybrids. Arachis cardenasii has been one of the most useful sources of genes from wild species to date, but crosses involving other species are being produced, in particular A. stenosperma and A. diogoi. The recent use of the two most probable ancestors of peanut A. duranensis and A. ipaënsis in a systematic introgression program opens the way for extensive and detailed characterization of the peanut genome and wild allele interactions for a wide range of traits. As new materials are being created and genotyping strategies are becoming more advanced, variability from the wild species is being harnessed to the benefit of world agriculture.