High molecular weight glutenin gene diversity in Aegilops tauschii demonstrates unique origin of superior wheat quality

AbstractCentral to the diversity of wheat products was the origin of hexaploid bread wheat, which added the D-genome of $\textit{Aegilops tauschii}$ to tetraploid wheat giving rise to superior dough properties in leavened breads. The polyploidization, however, imposed a genetic bottleneck, with only limited diversity introduced in the wheat D-subgenome. To understand genetic variants for quality, we sequenced 273 accessions spanning the known diversity of $\textit{Ae. tauschii}$. We discovered 45 haplotypes in $\textit{Glu-D1}$, a major determinant of quality, relative to the two predominant haplotypes in wheat. The wheat allele $\textit{2}$ + $\textit{12}$ was found in $\textit{Ae. tauschii}$ Lineage 2, the donor of the wheat D-subgenome. Conversely, the superior quality wheat allele $\textit{5}$ + $\textit{10}$ allele originated in Lineage 3, a recently characterized lineage of $\textit{Ae. tauschii}$, showing a unique origin of this important allele. These two wheat alleles were also quite similar relative to the total observed molecular diversity in $\textit{Ae. tauschii}$ at $\textit{Glu-D1}$. $\textit{Ae. tauschii}$ is thus a reservoir for unique $\textit{Glu-D1}$ alleles and provides the genomic resource to begin utilizing new alleles for end-use quality improvement in wheat breeding programs.