The sweet-potato genome contains genes from bacteria, so is an example of a naturally occurring genetically modified (GM) plant.

While combing through the genome of the domesticated sweet potato (Ipomoea batatas), Jan Kreuze of the International Potato Center in Lima, Peru, and his colleagues stumbled on genes that originated from one or more Agrobacterium species. These bacteria infect plants and transfer DNA into their hosts' genomes, so are used by researchers to genetically modify many agricultural crops. The two stretches of bacterial DNA found in the sweet potato are expressed in various tissues, and one of the sequences is found only in cultivated sweet potatoes — not in closely related wild strains.

These genes could encode traits that were desirable for domestication of the crop, and were probably transferred into an ancient sweet-potato ancestor, the authors say.

Proc. Natl Acad. Sci. USA (2015)