Wheat: Reconstitution of the Tetraploid Component (AABB) of Hexaploids.

The tetraploid AABB genomic component of two varieties of common hexaploid wheat (AABBDD; 2n = 42) was reconstituted by a simple back-crossing technique in which known phylogenetic relationships between the hexaploid and tetraploid groups of Triticum were used. The reconstituted tetraploids do not closely resemble commonly described varieties of the present-day group of tetraploid species. The plants are dwarfed, lack vigor, and are partially or completely self-sterile, depending on the variety of the hexaploid source. Chromosome pairing is similar to that observed in a variety of durum wheat (AABB; 2n = 28). Synthetic hexaploids derived from hybrids between one of the reconstituted tetraploids and several strains of Aegilops squarrosa (D genome) are of normal growth and vigr and are highly fertile.