Abstract
Maize (Zea mays ssp. mays) is not only one of the world’s most important crops, but it also is a powerful tool for studies of genetics, genomics, and cytology. The genome of maize shows the unmistakable signature of an ancient hybridization event followed by whole genome duplication (allopolyploidy), but the parents of this event have been a mystery for over a century, since studies of maize cytogenetics began. Here we show that the whole genome duplication event preceded the divergence of the entire genus Zea and its sister genus Tripsacum. One genome was donated, in whole or in part, by a plant related to the modern African genera Urelytrum and Vossia, although genomic rearrangement has been extensive. The other genome donor is less well-supported, but may have been related to the modern Rottboellia-Hemarthria clade, which is also African. Thus Zea and Tripsacum together represent a New World radiation derived from African ancestors.
