Bread wheat is an allohexaploid, instead of the original two sets (diploid). There are six sets of chromosomes, two sets from each of three different species.. Free-threshing wheat is closely related to spelt wheat. As with spelt, genes from goatgrass (Aegilops tauschii) give bread wheat greater cold hardiness than most wheats. It is cultivated throughout the world's temperate zones.
Of the six sets of chromosomes, two come from einkorn wheat and two from Aegilops speltoides. This hybridisation created the species Triticum turgidum, 580–820 thousand years ago. The last two sets of chromosomes came from Aegilops tauschii, 230–430 thousand years ago.
- Excellent resource for 20th century plant breeding.
- Standard reference for evolution and early history.
- Brenchley et al 2012. Analysis of the bread wheat genome using whole-genome shotgun sequencing. Nature 491 (7426): 705–10. 
- Mayer K.F.X. 2014. A chromosome-based draft sequence of the hexaploid bread wheat (Triticum aestivum) genome. Science 345 (6194): 
- Marcussen T. et al 2014. Ancient hybridizations among the ancestral genomes of bread wheat. Science 345 (6194): .