Aneuploids and the cytogenetic structure of wheat varietal populations

Riley, Ralph; Kimber, G.

doi:10.1038/hdy.1961.34

Cited by 65 publications

(36 citation statements)

References 12 publications

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“…Our results indicate that this might not be the case, and suggests that additional mechanisms are likely required for karyotype stabilization postallopolyploidization. Our findings, however, raise a conundrum, as all natural common wheat varieties are known to be chromosomally stable, producing only 1-3% aneuploid individuals under normal conditions (22). Thus, the mechanisms by which karyotype stabilization has been achieved in natural common wheat remain an open question.…”

Section: Discussionmentioning

confidence: 53%

Persistent whole-chromosome aneuploidy is generally associated with nascent allohexaploid wheat

Zhang

Bian

Gou

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

173

202

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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 wholechromosome 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.chromosome dynamics | hidden aneuploidy | synthetic wheat | wheat evolution H exaploid common wheat (Triticum aestivum L.) is a major food crop with international significance, the evolution of which is characterized by two sequential allopolyploidization events: one leading to formation of allotetraploid wheat (T. turgidum L.) and the other to allohexaploid wheat (T. aestivum) (1, 2). Despite decades of research, the mechanisms by which the initial allopolyploid individuals became stabilized, established, and accumulate to successful speciation remains largely unknown in this important crop. In theory, chromosome-level perturbation should be among the first manifestations of nascent allopolyploidization. Indeed, two recent molecular cytogenetic studies, in resynthesized allotetraploid Brassica napus lines (3) and young natural allotetraploid Tragopogon miscellus populations (4), respectively, have provided unique insights into the chromosomal dynamics associated with nascent allotetraploidy. Being at the resolution of individual chromosomes, these studies have documented a surprisingly high incidence of both structural and numerical changes in nascent allotetraploid plants (3, 4). It was found that early generations of resynthesized allotetrap...

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Section: Discussionmentioning

confidence: 53%

Persistent whole-chromosome aneuploidy is generally associated with nascent allohexaploid wheat

Zhang

Bian

Gou

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

173

202

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“…While in varietal populations of the natural polyploid bread wheat RiLEY and KIMBER (1961) estimated an average aneuploid frequency of 1.08 %, TSUCHIYA and LARTER (1969) found in the immediate progeny of euploid plants of advanced triticale strains a mean of 8.8 % aneuploid plants. Many reports on aneuploid frequency in triticale indicates that the value found by TSUCHIYA and LARTER can be taken to be representative.…”

Section: Is Triticale a Cytological Problem?mentioning

confidence: 99%

Triticale, Still a Promise?

Lelley

1992

Plant Breeding

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Experiments with primary triticale genotypes produced from defined wheat and rye parents provide a strong indication of a preponderance of specific genome combining ability in the phenotypic expression of triticale. Studying line families developed from specific cross combinations by means of the single seed descent method revealed that, in contrast to wheat, the distribution of genotypes in an F2 population of triticale is strongly skewed, with the majority of them being inferior to the mid-parent value. This is the case even if recombination is restricted to one fourth of one of the parental components of triticale, i.e. wheat or rye. Correlations of yield components were found to deviate substantially from known types of correlations in wheat, an established natural allopolyploid species. These findings give a strong indication for a genomic inbalance in triticale being a major cause for slow advance in varietal improvement. New breeding strategies designed for the specific genetic structure of triticale are necessary to accelerate breeding progress and to help triticale ultimately to live up to its promise.

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“…Riley and Kimber (1961) assumed a proportional participation in the asynapsis by the chromosomes belonging to different genomes. Our results were not in accord with that; B genome and 4A chromosomes play a more important part than expected in asynapsis.…”

Section: Discussionmentioning

confidence: 99%

“…Chromosome pairing at metaphase I in intercultivar hybrids of wheat is less regular than their corresponding parents, resulting in a higher frequency of cells with univalents and a lesser number of chiasma per cell (Hollingshead, 1932;Morrison, 1953;Person, 1956;Riley and Kimber, 1961;Watanabe, 1962;Röbbelen, 1968;Schlegel and Mettin, 1981).…”

Section: Introductionmentioning

confidence: 99%