Evolution of Setaria

Abstract

The genus Setaria includes almost 100 species of panicoid grasses. Within the subfamily Panicoideae it falls in the tribe Paniceae, subtribe Cenchrinae. Members of the subtribe are characterized by the presence of sterile branches in the inflorescence, often known as “bristles.” Major clades of Setaria are geographically localized, with the African species falling in a distinct clade from the South American ones, which are in turn distinct from the Asian ones. Many species have become weedy and are distributed widely in warm areas throughout the world. Nearly all members of the genus share a chromosome base number of x = 9, similar to most other members of Paniceae, and polyploidy is common, with some species including tetraploid, hexaploid, and octoploid members. The crop species S. italica was domesticated from the weed S. viridis, and both share a genome designated as A. A second diploid weed, S. adhaerens, is genomically distinct, with a genome designated as B. The tetraploid S. verticillata includes both A and B genomes, while tetraploid S. faberi appears to be derived from two A-like ancestors.