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Ipomoea batatas (L.) Lam., the sweet potato, is the most well-known and economically important member of the genus Ipomoea. Cultivated in all tropical and subtropical regions of the Globe (see FAOSTAT), it is among the ten most consumed crops worldwide and a staple in over twenty developing countries. In addition, its orange-fleshed varieties are rich in β-carotene, a major source of vitamin A for most people, and their consumption helps to address deficiencies related to this important nutrient affecting millions of children worldwide.

Despite its importance as a staple and after decades, if not centuries, of studies, many aspects of sweet potato evolution are still poorly understood. Important questions pertaining to the origin of the crop are only being answered now, for example, did the sweet potato have a single or a multiple origin? In addition, and taking into account that Ipomoea batatas is a hexaploid species (with all its wild relatives either diploid or tetraploid), did it originate by direct autopolyploidization from its wild ancestor or is it the result of hybridisation between different species?

I. batatas is the only hexaploid species known in the genus Ipomoea and the only species in its group of close relatives that develops edible storage roots. Using extensive taxon and data sampling, our group produced genomic-scale phylogenies that allow an accurate interpretation of the evolutionary relationships between sweet potato and its close relatives.

Batatas phylogeny

Our results show Ipomoea batatas belongs to a group of sixteen species (two of them hybrids, I. leucantha and I. tabascana), traditionally known as Ipomoea Series or Section Batatas. This group includes the sweet potato, fourteen species native to the American continent and another species native to Africa, Asia and the Pacific but absent from the Americas. These wild species closely related to the sweet potato are often referred to as the crop wild relatives:

In the beginning, Spanish speakers used the term “batata”, taken from indigenous Caribbean people, to refer to the sweet potato, and the term “papa”, of Andean origin, to refer to the potato. Some time during the 16th century, both terms mixed and the hybrid “patata” appeared, used without distinction for both crops. Subsequently, Europeans added other terms to differentiate both crops. Spanish language evolved into using “patata” for the potato and “batata” (with a B) or "boniato" for the sweet potato, whereas French speakers opted for using “patate douce” to distinguish the sweet potato from the “patate” (potato), which would later become “pomme de terre”… but that’s a different story.

The English term “sweet potato” is a strict translation from the French (“patate douce” literally means sweet potato) and “sweetpotato” all together is a corruption of the language that, in fact, appeared in recent times (isolated use in late 19th century and some more widespread in the late 20th century, but still much less frequent than sweet potato as two words).

Text last updated 20th December 2019.