title: Persistent whole-chromosome aneuploidy is generally associated with nascent allohexaploid wheat.
abstract: Allopolyploidization has been a driving force in plant evolution. Formation of common wheat (Triticum aestivum L.) represents a classic example of successful speciation via allopolyploidy. Nevertheless, the immediate chromosomal consequences of allopolyploidization in wheat remain largely unexplored. We report here an in-depth investigation on transgenerational chromosomal variation in resynthesized allohexaploid wheats that are identical in genome constitution to common wheat. We deployed sequential FISH, genomic in situ hybridization (GISH), and homeolog-specific pyrosequencing, which enabled unequivocal identification of each of the 21 homologous chromosome pairs in each of >1,000 individual plants from 16 independent lines. We report that whole-chromosome aneuploidy occurred ubiquitously in early generations (from selfed generation S(1) to >S(20)) of wheat allohexaploidy although at highly variable frequencies (20-100%). In contrast, other types of gross structural variations were scant. Aneuploidy included an unexpected hidden type, which had a euploid chromosome number of 2n = 42 but with simultaneous loss and gain of nonhomeologous chromosomes. Of the three constituent subgenomes, B showed the most lability for aneuploidy, followed by A, but the recently added D subgenome was largely stable in most of the studied lines. Chromosome loss and gain were also unequal across the 21 homologous chromosome pairs. Pedigree analysis showed no evidence for progressive karyotype stabilization even with multigenerational selection for euploidy. Profiling of two traits directly related to reproductive fitness showed that although pollen viability was generally reduced by aneuploidy, the adverse effect of aneuploidy on seed-set is dependent on both aneuploidy type and synthetic line.
authors: Key Laboratory of Molecular Epigenetics of the Ministry of Education,  Northeast Normal University, Changchun 130024,  China.
authors: Huakun
authors: H
authors: Zhang
authors: Yao
authors: Y
authors: Bian
authors: Xiaowan
authors: X
authors: Gou
authors: Bo
authors: B
authors: Zhu
authors: Chunming
authors: C
authors: Xu
authors: Bao
authors: B
authors: Qi
authors: Ning
authors: N
authors: Li
authors: Sachin
authors: S
authors: Rustgi
authors: Hao
authors: H
authors: Zhou
authors: Fangpu
authors: F
authors: Han
authors: Jiming
authors: J
authors: Jiang
authors: Diter
authors: D
authors: von Wettstein
authors: Bao
authors: B
authors: Liu
mesh_terms: D000782:Aneuploidy; D032461:Chromosomes, Plant / Q000235:genetics*; D003433:Crosses, Genetic; D007621:Karyotyping; D011058:Pollen / Q000502:physiology; D011123:Polyploidy; D015203:Reproducibility of Results; D012639:Seeds / Q000235:genetics / Q000254:growth & development; D017422:Sequence Analysis, DNA; D014022:Tissue Survival; D014908:Triticum / Q000235:genetics*
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