Genome Plasticity a Key Factor in the Success of Polyploid Wheat Under Domestication

Department of Plant Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA.
Science (Impact Factor: 33.61). 07/2007; 316(5833):1862-6. DOI: 10.1126/science.1143986
Source: PubMed

ABSTRACT Wheat was domesticated about 10,000 years ago and has since spread worldwide to become one of the major crops. Its adaptability to diverse environments and end uses is surprising given the diversity bottlenecks expected from recent domestication and polyploid speciation events. Wheat compensates for these bottlenecks by capturing part of the genetic diversity of its progenitors and by generating new diversity at a relatively fast pace. Frequent gene deletions and disruptions generated by a fast replacement rate of repetitive sequences are buffered by the polyploid nature of wheat, resulting in subtle dosage effects on which selection can operate.

Download full-text


Available from: Jan Dvorak, Apr 01, 2014
1 Follower
108 Reads
  • Source
    • "dicoccum (2n = 4x =28, AABB) c. 9000 yr ago (Nesbitt & Samuel, 1996). During the course of cultivation of domesticated tetraploid wheat T. dicoccum (AABB), it hybridized with diploid species Aegilops tauschii (2n = 2x = 14, DD) to form hexaploid wheat, T. aestivum (2n = 6x =42, AABBDD) (McFaden & Sears, 1946; Dvorak, 1976; Dubcovsky & Dvorak, 2007; Matsuoka, 2011). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Preharvest sprouting (PHS) is one of the major constraints of wheat production in areas where prolonged rainfall occurs during harvest. TaPHS1 is a gene that regulates PHS resistance on chromosome 3A of wheat, and two causal mutations in the positions +646 and +666 of the TaPHS1 coding region result in wheat PHS susceptibility. Three competitive allele-specific PCR (KASP) markers were developed based on the two mutations in the coding region and one in the promoter region and validated in 82 wheat cultivars with known genotypes. These markers can be used to transfer TaPHS1 in breeding through marker-assisted selection. Screening of 327 accessions of wheat A genome progenitors using the three KASP markers identified different haplotypes in both diploid and tetraploid wheats. Only one Triticum monococcum accession, however, carries both causal mutations in the TaPHS1 coding region and shows PHS susceptibility. Five of 249 common wheat landraces collected from the Fertile Crescent and surrounding areas carried the mutation (C) in the promoter (−222), and one landrace carries both the causal mutations in the TaPHS1 coding region, indicating that the mis-splicing (+646) mutation occurred during common wheat domestication. PHS assay of wheat progenitor accessions demonstrated that the wild-types were highly PHS-resistant, whereas the domesticated type showed increased PHS susceptibility. The mis-splicing TaPHS1 mutation for PHS susceptibility was involved in wheat domestication and might arise independently between T. monococcum and Triticum aestivum.
    New Phytologist 08/2015; DOI:10.1111/nph.13489 · 7.67 Impact Factor
    • "Over the years, this phenomenon has been the focus ofsubstantial and diverse research. In fact, it has played a crucial role in the domestication ofcrops, such as wheat, maize and cotton (Dubcovsky and Dvorak, 2007). Recently, in additionto the aspects that have been studied in polyploidy, one of the more intriguing questions has been how the genetic diversity within and between populations of wild polyploid plantspecies is partitioned and what are the factors determining their genetic structure. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Brachypodium hybridum has recently been recognized as an allotetraploid species deriving from natural hybridization between B. distachyon and B. stacei. The identification of this species which emerged as a new model for polyploid species has spawned considerable scientific interest. A lot of investigations using highly variable markers and a broad geographical sampling are underway to understand the patterns of their genetic diversity and the contribution of polyploidy to adaptation. As a step towards understanding the genetic basis for natural variation of this species in Tunisia, 15 microsatellite markers and 145 genotypes representing 9 natural populations were used. Results exhibit a high level of polymorphism (159 polymorphic alleles with an average of 8.6 alleles per locus) and high level of genetic diversity in all the studied populations with expected and observed heterozygosities averaging 0.79 and 0.31, respectively. AMOVA resulted in a high variation within population (97%) and altitude as compared to the variation among populations (3%, Φ PT = 0.023), altitude and eco-region. Results also showed that the 9 populations grouped into 3 clusters without geographical or altitudinal clustering. This grouping was accompanied by a high rate of gene flow between populations (Nm = 2.31). Interestingly, Mantel test identified that the extent of genetic differentiation was not correlated to geographic distances (r = 0.046; p = 0.78) nor to the altitudinal differences (r = -0.29; p = 0.75). In the present study we report a high rate of successful cross-amplification of B. distachyon SSR markers in B. hybridum, which implies the great transferability between these two species. Moreover, genetic characterization of the Tunisian populations of B. hybridum by SSR markers suggests that the spatial genetic structure of this species may be affected by a multidirectional gene flow via long-distance seed dispersal, leading to a weak genetic structure.
    Flora - Morphology Distribution Functional Ecology of Plants 08/2015; DOI:10.1016/j.flora.2015.08.001 · 1.47 Impact Factor
  • Source
    • "monococcum ) and emmer wheat (Triticum turgidum subsp. dicoccum; Salamini et al. 2002; Dubcovsky and Dvorak 2007; Brown et al. 2008; Faris 2014). "
    [Show abstract] [Hide abstract]
    ABSTRACT: Wheat domestication was a crucial step in the evolution of stable human societies. The loss of rachis brittleness is a major change that differentiates the earliest forms of domesticated wheat from their wild ancestors. We recently identified a novel quantitative trait locus (QTL) for rachis fragility on the long arm of chromosome 3D using an F2 mapping population derived from the cross between Triticum aestivum ‘Chinese Spring’ (CS) and a synthetic wheat line, S-6214. Here, we show that the QTL region, in the deletion bin 3DL2-0.27-0.81, is syntenous to the rice chromosome 1 region harboring the seed shattering gene qSH1. We isolated the wheat qSH1 ortholog, TaqSH1-D, on chromosome 3DL. The gene mapped into the confidence interval of the rachis fragility QTL, indicating that it represents a potential candidate gene. Sequence comparison between the parental lines revealed a 189-bp repetitive sequence insertion located 275 bp downstream of the translation termination site of the gene in CS. Although the putative parental proteins are identical, as in rice, a polymorphism in the regulatory regions may specifically affect its control of rachis fragility.
    Genetic Resources and Crop Evolution 07/2015; DOI:10.1007/s10722-015-0301-z · 1.46 Impact Factor
Show more