The natural occurrence of the genus Arachis is limited to five countries, i.e., Argentina, Bolivia, Brazil,
Paraguay, and Uruguay. The headwaters of the Paraguay river in the region of Mato Grosso is considered
to be the center of origin of the genus. The taxonomy of the genus is not well delineated and the grouping of species into seven sections is only tentative; there may be as many as 70
... [Show full abstract] species in the genus Arachis. The cultivated groundnut, Arachis hypogaea L., originated in an area of southern Bolivia and northwestern Argentina on the eastern slopes of the Andes. This species is subdivided into subspecies and botanical varieties that have been found to have a specific geographic distribution in South America. Groundnut rust, caused by Puccinia arachidis Speg., is one of the major diseases of groundnut. It probably originated in South America and evolved along with the host species.
Most of the 39 groundnut accessions identified as rust-resistant at ICRISAT belong to the ribbed Valencia
type and originated in Peru. So it is concluded that resistance to rust in the cultivated groundnut may have also originated in Peru. Hence there is a need for pointed collection in Peru to enrich and broaden the available gene pool. Wild Arachis species belonging to different sections have been found to be either
resistant or immune to rust. Efforts are under way to utilize such resistance for groundnut improvement.
Observations in the native habitat have indicated that wild Arachis might be infected by rust and other
diseases to a greater extent than expected. More research is required in South America to investigate possible pathogenic variation and resistance to rust in wild Arachis species.
