Abstract
Common wheat (Triticum aestivum L., AABBDD genome) is thought to have emerged through natural hybridization between Triticum turgidum L. (AABB genome) and Aegilops tauschii Coss. (DD genome). Hybridization barriers and doubling of the trihaploid F1 hybrids’ genome (ABD) via unreduced gamete fusion had key roles in the process. However, how T. turgidum, the maternal progenitor, was involved in these mechanisms remains unknown. An artificial cross‐experiment using 46 cultivated and 31 wild T. turgidum accessions and a single Ae. tauschii tester with a very short genetic distance to the common wheat D genome was conducted. Cytological and quantitative trait locus analyses of F1 hybrid genome doubling were performed. The crossability and ability to cause hybrid inviability did not greatly differ between the cultivars and wild accessions. The ability to cause hybrid genome doubling was higher in the cultivars. Three novel T. turgidum loci for hybrid genome doubling, which influenced unreduced gamete production in F1 hybrids, were identified. Cultivated T. turgidum might have increased the probability of the emergence of common wheat through its enhanced ability to cause genome doubling in F1 hybrids with Ae. tauschii. The ability enhancement might have involved alterations at a relatively small number of loci.
Highlights
Common wheat (Triticum aestivum L.; AABBDD genome) is the most widely grown crop worldwide
Common wheat is thought to have emerged through natural hybridization of Triticum turgidum L. (AABB genome) as the maternal progenitor and Aegilops tauschii Coss. as the paternal progenitor (Kihara, 1944; McFadden & Sears, 1944)
In a widely accepted scenario for the origin of common wheat, cultivated T. turgidum, which met with Ae. tauschii through human-mediated migration associated with the spread of agriculture across and beyond the Fertile Crescent, is considered the female progenitor, based mainly on the fact that no wild form of T. aestivum has ever been found (Kihara, 1966, 1975)
Summary
Common wheat (Triticum aestivum L.; AABBDD genome) is the most widely grown crop worldwide. Ae. tauschii is polymorphic in its ability to cause reproductive barrier expression in the cross with T. turgidum and unreduced gamete production in F1 hybrids (Matsuoka et al, 2007) This suggests that some genotypes of Ae. tauschii may have had more opportunities to be involved in the origin of common wheat than others because they frequently hybridized with T. turgidum and because the F1 hybrids were likely to produce unreduced gametes. In the artificial cross-experiment, a diverse array of T. turgidum accessions were crossed with a single Ae. tauschii tester accession with a very short genetic distance to the D genome of common wheat, with the aim to evaluate the natural variation patterns of crossability with Ae. tauschii and the abilities to cause inviability and genome doubling in F1 hybrids. On the basis of these findings, we discuss insights into the role of T. turgidum in the evolution of common wheat
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