Differential effects of Aegilops tauschii genotypes on maturing-time in synthetic hexaploid wheats

Bread wheat (Triticum aestivum) is a hexaploid species with A, B and D genomes. Therefore, most bread wheat genes are present in the genome as triplicated homoeologous genes (homoeologs) derived from the ancestral A, B, and D genome diploid species. Maturing-time, which is associated with flowering-time and the grain-filling period, is one of the most important agronomic traits for wheat breeding. Here, the effects of homoeologs derived from D genome diploid species on maturing-time in bread wheat were examined in synthetic hexaploid wheats obtained by crossing tetraploid durum wheat T. turgidum ssp. durum cv. Langdon and three accessions of the D genome diploid species (Aegilops tauschii). After vernalization, the synthetic hexaploid wheat derived from an early-flowering D genome donor showed an early-flowering phenotype among the synthetic hexaploids, whereas the synthetic wheat derived from a late-flowering D genome donor was late-flowering among the synthetic hexaploids. This suggests that the early-flowering phenotype in hexaploid wheat is affected by the homoeolog for early-flowering in the D genome donor. In contrast, maturing-time and grain-filling period in the synthetic hexaploids did not correspond with those of the D genome donors, suggesting that these traits are controlled by the interaction between homoeologs on the A, B and D genomes in hexaploid wheat.