Durum wheat as a candidate for the unknown female progenitor of bread wheat:: an empirical study with a highly fertile F1 hybrid with Aegilops tauschii Coss.

(H)exaploid bread wheat was derived from a hybrid cross between a cultivated form of tetraploid Triticum wheat (female progenitor) and a wild diploid species, Aegilops tauschii Coss. (male progenitor). This cross produced a fertile triploid F-1 hybrid that set hexaploid seeds. The identity of the female progenitor is unknown, but various cultivated tetraploid Triticum wheats exist today. Genetic and archaeological evidence suggests that durum wheat (T. turgidum ssp. durum) may be the female progenitor. In previous studies, however, F-1 hybrids of durum wheat crossed with Ae. tauschii consistently had low levels of fertility. To establish an empirical basis for the theory of durum wheat being the female progenitor of bread wheat, we crossed a durum wheat cultivar that carries a gene for meiotic restitution with a line of Ae. tauschii. F-1 hybrids were produced without using embryo rescue techniques. These triploid F-1 hybrids were highly fertile and spontaneously set hexaploid F-2 seeds at the average selfed seedset rate of 51.5%. To the best of our knowledge, this is the first example of the production of highly fertile F-1 hybrids between durum wheat and Ae. tauschii. The F-1 and F-2 hybrids are both similar morphologically to bread wheat and have vigorous growth habits. Cytological analyses of F-1 male gametogenesis showed that meiotic restitution is responsible for the high fertility of the triploid F-1 hybrids. The implications of these findings for the origin of bread wheat are discussed.