Fraction 1 Protein and the Origin of Polyploid Wheats

The nature of the interspecific hybridizations giving rise to the polyploid wheats has been determined from an analysis of the polypeptide compositions of fraction 1 proteins isolated from diploid, tetraploid, and hexaploid wheat species. In the origins of the tetraploid wheat, the B-genome donor provided the chloroplast genome and was therefore the maternal parent in the cross with Triticum monococcum . Subsequently, the tetraploid wheat, T. dicoccum , was the maternal parent in the cross with Aegilops squarrosa , giving rise to the hexaploid wheat, T. aestivum . Of the small number of diploid species examined, only Ae. speltoides has a chloroplast genome similar to that of the polyploid wheats.