Natural variation for fertile triploid F₁ hybrid formation in allohexaploid wheat speciation

• Published in: Theoretical and applied genetics Vol. 115; no. 4; pp. 509 - 518
• Main Authors: Matsuoka, Yoshihiro, Takumi, Shigeo, Kawahara, Taihachi
• Format: Journal Article
• Language: English
• Published: Heidelberg Berlin/Heidelberg : Springer-Verlag 01.08.2007; Berlin Springer; Springer Nature B.V
• Subjects: Biological and medical sciences; Biological Evolution; Classical genetics, quantitative genetics, hybrids; DNA, Chloroplast - genetics; Fertility - genetics; Fundamental and applied biological sciences. Psychology; Genetic Variation; Genetics of eukaryotes. Biological and molecular evolution; Haplotypes; Hybridization, Genetic; Phenotype; Phylogeny; Polyploidy; Pteridophyta, spermatophyta; Reproduction - genetics; Species Specificity; Triticum - genetics; Triticum - physiology; Vegetals; Wheat; Monocotyledones; Gramineae; Angiospermae; F1 hybrid; Genetics; Spermatophyta; Agriculture; Speciation; Triticum aestivum
• ISSN: 0040-5752; 1432-2242
• DOI: 10.1007/s00122-007-0584-3

The tempo, mode, and geography of allopolyploid speciation are influenced by natural variation in the ability of parental species to express postzygotic reproductive phenotypes that affect hybrid fertility. To shed light on the impact of such natural variations, we used allohexaploid Triticum aestivum wheats' evolution as a model and analyzed the geographic and phylogenetic distributions of Aegilops tauschii (diploid progenitor) accessions involved in the expression of abnormality and fertility in triploid F₁ hybrids with Triticum turgidum (tetraploid progenitor). Artificial-cross experiments and chloroplast-DNA-based evolutionary analyses showed that hybrid-abnormality-causing accessions had limited geographic and phylogenetic distributions, indicative that postzygotic hybridization barriers are underdeveloped between these species. In contrast, accessions that are involved with fertile triploid F₁ hybrid formation have wide geographic and phylogenetic distributions, indicative of a deep evolutionary origin. Wide-spread hybrid-fertilizing accessions support the theory that T. aestivum speciation occurred at multiple sites within the species range of Ae. tauschii, in which existing conditions enabled natural hybridization with T. turgidum. Implications of our findings on how natural variation in the ability of Ae. tauschii to express those postzygotic reproductive phenotypes diversified and contributed to the speciation of T. aestivum are discussed.