Shaping polyploid wheat for success: Origins, domestication, and the genetic improvement of agronomic traits.

Bread wheat (Triticum aestivum L., AABBDD, 2n = 6x = 42), which accounts for most of the cultivated wheat crop worldwide, is a typical allohexaploid with a genome derived from three diploid wild ancestors. Bread wheat arose and evolved via two sequential allopolyploidization events and was further polished through multiple steps of domestication. Today, cultivated allohexaploid bread wheat has numerous advantageous traits, including adaptive plasticity, favorable yield traits, and extended end-use quality, which have enabled its cultivation well beyond the ranges of its tetraploid and diploid progenitors to become a global staple food crop. In the past decade, rapid advances in wheat genomic research have considerably accelerated our understanding of the bases for the shaping of complex agronomic traits in this polyploid crop. Here, we summarize recent advances in characterizing major genetic factors underlying the origin, evolution, and improvement of polyploid wheats. We end with a brief discussion of the future prospects for the design of gene cloning strategies and modern wheat breeding.