Amazonia is a major world centre of plant domestication, and manioc or cassava (Manihot esculenta, Euphorbiaceae) is currently the most important staple food crop that originated in this region. However, little is known about the dispersal of its two major cultivated groups (bitter and sweet manioc).
Alves-Pereira et al. evaluate the genetic diversity and structure of manioc along major Amazonian rivers using chloroplast and nuclear molecular markers. Bitter and sweet manioc have distinctive patterns of genetic structure across rivers, suggesting that they had distinct dispersal histories. Knowledge about how Amazonian people manage their crops is valuable for the maintenance and conservation of the impressive diversity of their native Amazonian genetic resources.