History of Propagation and Genetic Structures in Three Japanese Millets: Proso Millet, Foxtail Millet, and Barnyard Millet

Currently, rice is a staple food in Eastern Eurasia, but historically, millet has also been an important grain. Proso millet, foxtail millet, and Japanese barnyard millet were domesticated from wild plants in East Asia. Cultivation of these millets expanded over large areas of the world because they can adapt to colder regions at higher latitudes than other cereals. Millet cultivation has historically been as important as rice cultivation in Yaponesia because the northern limit of rice cultivation is located within the country. In northern Yaponesia, Japanese barnyard millet might have been in use by 7000 BC and domesticated by 2700 BC. At approximately 1000 BC, rice, proso millet, and foxtail millet were introduced into Yaponesia from the Eurasian continent. Subsequently, rice has become the staple food of the Yaponesian population, but the three aforementioned millets have also been traditionally important in Yaponesia, especially as the main carbohydrates in the diet of northern Yaponesia. These three millets have evolved in East Asia through domestication via unconscious selection regarding farming and food processing methods. Furthermore, evolution of the response to day length is essential for these millets to adapt to different latitudinal environments, which would have influenced their historical propagation.