The Problem of the Origin of Subgenomes B, A, and D of Bread Wheat Triticum aestivum L.: Old Facts and New Evidences

Abstract—Common hexaploid wheat (Triticum aestivum L.) belongs to the tribe of wheat, which includes representatives of the genera Triticum, Aegilops, Secale, Hordeum, etc. The genera Aegilops and Triticum repeatedly hybridized with each other in the process of evolution, including with the formation of polyploid forms that have the status of species and belong to the so-called Triticum–Aegilops alliance. With the development of a methodological possibilities, different approaches were used to determine the ancestors of certain species of this alliance, starting directly from interspecific crosses and cytogenetic methods and ending with whole genome sequencing of non-nuclear and nuclear genomes. It was established that the genome of the bread wheat T. aestivum (one of the main food crops of the world) consists of three related subgenomes that received the symbols A, B, and D. At present, only the donor of the D subgenome (which is Aegilops tauschii Coss) is reliably known. The T. urartu Thum. ex Gandil is presumably considered to be an ancestor of the A subgenome. Information about the donor of the B subgenome is less clear; however, it is most likely Ae. speltoides Tausch. or a species close to it. This review is devoted to the consideration of some old data on the putative donors of the bread wheat, which has (taking into account the maternal form) the BBAADD genome, and to the clarification of some phylogenetic relationships in the Triticum–Aegilops alliance in the light of new information obtained as a result of genome-wide studies of wheat.