The Independent Domestication of Timopheev's Wheat: Insights from Haplotype Analysis of the () Gene.

and are two tetraploid wheat species sharing as a common ancestor, and domesticated accessions from both of these allopolyploids exhibit nonbrittle rachis (i.e., nonshattering spikes). We previously described the loss-of-function mutations in the genes and in the A and B subgenomes, respectively, that are responsible for this most visible domestication trait in . Resequencing of a large panel of wild and domesticated accessions subsequently led to the identification of the two progenitor haplotypes of the and domesticated alleles. Here, we extended the haplotype analysis to other subspecies and to the homologues in the related species. Our results showed that all the domesticated wheat subspecies within share common and haplotypes, confirming their common origin. In , however, we identified a novel loss-of-function allele underlying a partially brittle spike phenotype. This novel recessive allele appeared fixed within the pool of domesticated Timopheev's wheat but was also carried by one wild accession exhibiting partial brittleness. The promoter region for could not be amplified in any accessions with any primer combination, exemplifying the gene-level distance between the two species. Altogether, our results support the concept of independent domestication processes for the two polyploid, wheat-related species.