Wheat: Recent Advances in Genomics to Explore the History of Domestication and Polyploidization

Wheat is cultivated in the largest area among the crop species. The geographic spread of wheat since its domestication in the Middle East approximately 10,000 years ago has attracted a broad interest in biology and archaeology. The spread of wheat associated with the migration of farmers and languages has been proposed. However, the complexity of the wheat genome due to polyploidization has been an obstacle in studying the domestication and spread of wheat using genetic data. In this chapter, we introduce domesticated wheat species in the context of polyploidization and then summarize recent genomic studies on the independent domestication events of three wheat species: Einkorn, Emmer, and Timopheevi. Population genetic studies supported the origin place of Einkorn and Emmer in the northern part of the Fertile Crescent and the importance of gene flow. Approximately 8000 years ago, common wheat emerged through a further polyploidization event, followed by its spread westward to Europe and eastward to East Asia, including Japan. We discuss the potential of growing genomic data, together with archaeobotanical studies and ancient or historical genomics, to reveal the longstanding question of wheat domestication and spread.