QTug.sau-3B is a major quantitative trait locus for wheat hexaploidization.
Bottom Line: Meiotic nonreduction resulting in unreduced gametes is thought to be the predominant mechanism underlying allopolyploid formation in plants.Comparative genome analysis indicated that this QTL was close to Ttam-3B, a collinear homolog of tam in wheat.Although the relationship between QTug.sau-3B and Ttam requires further study, high frequencies of unreduced gametes may be related to reduced expression of Ttam in wheat.
Affiliation: Triticeae Research Institute, Sichuan Agricultural University at Chengdu, Wenjiang, Sichuan 611130, People's Republic of China.Show MeSH
Mentions: To investigate the reason for the difference in hexaploidization capacity between T. turgidum×Ae. tauschii hybrids, conventional staining and FISH using centromere probe 6C6-3 were used to observe meiosis in PMCs of the hybrids. At early metaphase I, the chromosomes generally appeared as univalents (Figure 3A), indicating that homeologous pairing was rare because of the presence of the Ph1 gene in T. turgidum (Okamoto 1957; Riley and Chapman 1958). In subsequent meiotic processes, we observed FDR and formation of dyads (Figure 3, B–H). The observed univalent behaviors among the analyzed PMCs of the three hybrid combinations suggest that FDR might have two pathways: (1) univalents were aligned on the equator at metaphase I (Figure 3B), followed by separation of sister chromatids (Figure 3C); and (2) univalents were not aligned on the equator and, when they began to split into sister chromatids, they remained connected at the centromeres (Figure 3D). They then formed a restitution nucleus (Figure 3E) and subsequently congregated on the equator (Figure 3F). Chromosomes underwent equational division at anaphase and dyad daughter cells were the only final products (Figure 3, G and H; Figure 4). In the LDN×AS60 hybrids, FDR predominated in all analyzed PMCs (Figures 4, A and B). FDR was also observed in the AS313×AS60 and the AS2255×AS60 hybrids; however, a large number of PMCs in the two hybrid combinations did not undergo meiotic restitution and produced triads and tetrads that might have undergone standard meiotic division (Figures 4, C and D).
Affiliation: Triticeae Research Institute, Sichuan Agricultural University at Chengdu, Wenjiang, Sichuan 611130, People's Republic of China.