Hexaploid bread wheat can be created from Triticum tauschii and Emmer strains. The genotype of T. tauschii is DD, while the genotype of Emmer wheat is AA BB. When we cross these two strains:
AA BB x DD
The progeny is ABD with one gamete or one chromosome of each type.
This progeny is then treated with colchicine. Colchicine is a chemical, which causes the doubling of chromosomes when applied. When colchicine is applied to the progeny of genotype ABD, we get a progeny of genotype AA BB DD.
This is the genotype of the hexaploid bread wheat.