Genetic mapping of quantitative trait loci for resistance to haemonchus contortus in sheep

K. Marshall, J. F. Maddox, Hong Lee, Y. Zhang, L. Kahn, H. U. Graser, C. Gondro, S. W. Walkden-Brown, J. H.J. Van Der Werf

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Summary This paper presents results from a mapping experiment to detect quantitative trait loci (QTL) for resistance to Haemonchus contortus infestation in merino sheep. The primary trait analysed was faecal worm egg count in response to artificial challenge at 6 months of age. In the first stage of the experiment, whole genome linkage analysis was used for broad-scale mapping. The animal resource used was a designed flock comprising 571 individuals from four half-sib families. The average marker spacing was about 20 cM. For the primary trait, 11 QTL (as chromosomal/family combinations) were significant at the 5% chromosome-wide level, with allelic substitution effects of between 0.19 and 0.38 phenotypic standard deviation units. In general, these QTL did not have a significant effect on faecal worm egg count recorded at 13 months of age. In the second stage of the experiment, three promising regions (located on chromosomes 1, 3 and 4) were fine-mapped. This involved typing more closely spaced markers on individuals from the designed flock as well as an additional 495 individuals selected from a related population with a deeper pedigree. Analysis was performed using a linkage disequilibrium-linkage approach, under additive, dominant and multiple QTL models. Of these, the multiple QTL model resulted in the most refined QTL positions, with resolutions of <10 cM achieved for two regions. Because of the moderate size of effect of the QTL, and the apparent age and/or immune status specificity of the QTL, it is suggested that a panel of QTL will be required for significant genetic gains to be achieved within industry via marker-assisted selection.

Original languageEnglish
Pages (from-to)262-272
Number of pages11
JournalAnimal Genetics
Issue number3
Publication statusPublished - 1 Jun 2009
Externally publishedYes


  • Disease resistance
  • Genome scan
  • Haemonchus contortus
  • Linkage analysis
  • Linkage disequilibrium-linkage analysis
  • Nematodes
  • Quantitative trait loci
  • Sheep

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Genetics

Cite this

Marshall, K., Maddox, J. F., Lee, H., Zhang, Y., Kahn, L., Graser, H. U., ... Van Der Werf, J. H. J. (2009). Genetic mapping of quantitative trait loci for resistance to haemonchus contortus in sheep. Animal Genetics, 40(3), 262-272.