Biodiversity in the Genus Arachis: Its Collection, Preservation, Distribution, Evaluation and Utilization.

Biodiversity in Arachis L. -- the Peanut Genus.

The biodiversity story in Arachis is two very different stories. The cultigen, Arachis hypogaea L. has a narrow genetic base. The species is relatively young (ca. 3 to 4,000 y). With the morphological characters of the six different botanical varieties one would think there would be significant genetic (molecular) diversity. However, that is not the case. Until molecular techniques became more sophisticated, almost no diversity could be detected in peanut. With more advanced techniques now available differences are apparent, but nothing like other crops. When the wild relatives of the cultigen are evaluated, a different picture is seen. Even without molecular analyses, the richness of the diversity within the wild relatives of the cultigen, can be seen in the vastly different environments where they have evolved. Three species (there may be more) grow in the extremely dry part of Northeast Brazil. The rainy season there consists of very short rain events, usually only a few times each year, and yet these species are perennial or semi-perennial and survive from year to year, only producing seed when the rain events extend into a few weeks. Other species have evolved to survive in well drained schist rock hillsides, wet in the rainy season, quite dry during the dry season. Still other species have evolved to survive in the Pantanal, a very large swamp that is usually inundated. Another species that we are using as a bridge species in the introgression program grows in an inundated swamp with tufts of grass growing one meter high and in 15 cm of water. The Arachis plants grow on top of the grass, branching from the main axis, flowering and making fruit that grow on a long hollow peg down into the muddy clay, black soil. This diversity is aiding in the improvement of the cultigen.