The closest wild relatives of cassava (Manihot esculenta Crantz)

The origin of cassava has long eluded researchers. The botanical origin, the geographical origin, the area of domestication, all are disputed matters. The argument advanced here is that, once the wild ancestor is identified, speculation about the taxonomy and the geographical cradle of the root crop will narrow considerably, as a number of species and geographical areas will automatically become excluded from consideration in matters of classification, domestication and evolution. Current knowledge about the three subjects shows that discoveries on the botanical origin of manioc have progressed a great deal, discoveries on the geographical origin are in progress, and discoveries on the area where the beginning of cultivation happened are incipient. In this paper, five Brazilian Manihot species are suggested as the closest wild relatives of cassava. One of them (M. esculenta ssp. flabellifolia) is regarded as the wild progenitor of modern cultivars and thus part of the primary genepool of the root crop. Another species (M. pruinosa) is regarded as the nearest species to the GP1 of cassava and can hardly be separated from the wild strain M. esculenta ssp. flabellifolia on morphological grounds.