Origin of wheat as a hexaploid

    The ancestor of modern Wheat (Triticum aestivum) is believed to be an interspecies hybrid of two species of Triticum, T. monococcum and T. searsi, which contributed chromosome sets A and B, respectively.This lead to a stable autopolyploid tetraploid by genome duplication, an AABB plant that produces AB gametes. A cross between this tetraploid an another diploid species, T. tauschii (chromosome set D) produced an allopolyploid triploid (ABD), which again underwent a genome duplication, and produced modern T. aestivum, a hexaploid with an  AABBDD chromosome set. The hexaploid chromosome set has become diploidized, which is to say that homologous chromosomes in each of the A, B, and D sets diverge genetically from each other so that they behave separately during meiosis.

    Triticale is a tetraploid hybrid of Wheat (Triticum) and Rye (Secale) that combines the desirable grain qualities of Wheat with the hardiness of Rye. In the Star Trek episode The Trouble with Tribbles, a main plot element is a supply of "Quadro-triticale" intended for use on a planet disputed by the Federation and Klingons. The "Quadro" may refer to further tetra-polyploidization

Figure ©2002 by Griffiths et al.; all text material ©2014 by Steven M. Carr