Haplotype variations of gene Ppd-D1 in Aegilops tauschii and their implications on wheat origin

The Ppd-D1 controlling photoperiod response is an important gene for wheat adaptation since it affects heading time. In the present study, three haplotypes, i.e. haplotype I without deletion, haplotype II with a 24?bp deletion, and haplotype III with two deletions of 24 and 15?bp, were identified in the upstream of the coding region in 80 Ae. tauschii accessions. The haplotype distribution was related to subspecies taxon. All typical ssp. tauschii accessions had haplotype I, whereas all ssp. strangulata had haplotype III. The three haplotypes were observed in Ae. tauschii with morphologically intermediate forms between the two typical subspecies. Present results supported that ssp. strangulata or intermediate form was the D-genome donor of common wheat since only haplotype III were found in wheat. Moreover, a 16?bp deletion in exon 8 of gene Ppd-D1 exists in common wheat. However, none of Ae. tauschii accessions analyzed had the 16?bp deletion.