Abstract
Plants have repeatedly undergone whole-genome duplication during their evolutionary history. Even in modern plants, there is diversity in ploidy within and between species, providing a snapshot of the evolutionary turnover of ploidy. Here, I will review the diversity of ploidy and the evolution of the genome constitution, focusing on the millet species Setaria italica, Panicum miliaceum, and Echinochloa esculenta. These are all historically important cereal crops that have been domesticated in East Asia. They all display a basic chromosome set of nine, but they are diploid, tetraploid, and hexaploid, respectively. The timing of ploidy is different among the millet species, as is the extent of gene family expansion and gene loss. There also exists complex subgenomic evolution in the wild species within each genus. These three millet species and their related wild species are suitable models for elucidating the molecular evolution and diversity of genome duplication by comparative genomic analysis.