Low levels of linkage disequilibrium in wild barley (Hordeum vulgare ssp. spontaneum) despite high rates of self-fertilization

Peter L. Morrell, Donna M. Toleno, Karen E. Lundy, Michael T. Clegg

Research output: Contribution to journalArticlepeer-review

145 Scopus citations

Abstract

High levels of inbreeding cause populations to become composed of homozygous, inbred lines. High levels of homozygosity limit the effectiveness of recombination, and therefore, retard the rate of decay of linkage (gametic phase) disequilibrium (LD) among mutations. Inbreeding and recombination interact to shape the expected pattern of LD. The actual extent of nucleotide sequence level LD within inbreeding species has only been studied in Arabidopsis, a weedy species whose global range has recently expanded. In the present study, we examine the levels of LD within and between 18 nuclear genes in 25 accessions from across the geographic range of wild barley, a species with a selfing rate of ≈98%. In addition to examination of intralocus LD, we employ a resampling method to determine whether interlocus LD exceeds expectations. We demonstrate that, for the majority of wild barley loci, intralocus LD decays rapidly, i.e., at a rate similar to that observed in the outcrossing species, Zea mays (maize). Excess interlocus LD is observed at 15% of two-locus combinations; almost all interlocus LD involves loci with significant geographic structuring of mutational variation.

Original languageEnglish (US)
Pages (from-to)2442-2447
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume102
Issue number7
DOIs
StatePublished - Feb 15 2005

Keywords

  • Inbreeding
  • Interlocus linkage disequilibrium
  • Nucleotide polymorphism
  • Population structure
  • Wall's B

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