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QTL for number of teats in a Merino/Romney mapping flock

QTL for number of teats in a Merino/Romney mapping flock. Ken Dodds Hannah Henry Anne Beattie Grant Montgomery AgResearch, Invermay, NZ. Polythelia in sheep. Alexander Graeme Bell ( Science 1899). Polythelia in sheep. Little attention until more recently

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QTL for number of teats in a Merino/Romney mapping flock

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  1. QTL for number of teats in a Merino/Romney mapping flock Ken Dodds Hannah Henry Anne Beattie Grant Montgomery AgResearch, Invermay, NZ

  2. Polythelia in sheep • Alexander Graeme Bell (Science 1899)

  3. Polythelia in sheep • Little attention until more recently • Prompted by increasing prolificacy • Maijala and Kyle (1988) • Finnish Landrace ewes in Finland • Coopworth ewes in New Zealand • Incidence ~ 20% • h2 = 0.60 • 1 to 3 genes ?

  4. Polythelia in other farm animals • Cattle • h2 0.43-0.45 • Pigs • h2 0.3 • Polygenic + single gene - best model • 1-3 QTL in 6 studies

  5. Genome Scan … … • Animals • Reciprocal backcross design High Fleece Weight Romney Ewe Superfine Merino Ram Romney Ewes Merino Ewes 3/4M1/4R Progeny (MRM) n100 3/4R1/4M Progeny (MRR) n100 4 families with this structure: 801-804

  6. Genome Scan • Phenotype • Observed during 1st 12 months • Belly and hind legs • Male and female • Markers • 220 (spaced) + 28 (wool candidates) • ~ 20cM spacing • 50% genotyped – primary screen • 100% genotyped – regions for wool

  7. Incidence

  8. Genome Scan Results • Genomewise significance found by permutation • Within family results • 12 regions > suggestive MRM+R • 2 regions > suggestive in one BC • Significant regions on two chromosomes

  9. Genome Scan Results OAR6 MRM+R

  10. Genome Scan Results OAR6 MRM+R

  11. Genome Scan Results OAR6 MRM+R Effects 0.70 (0.12) 0.37 (0.12)

  12. Genome Scan Results OAR6 MRM Effects 0.91 (0.19)

  13. Genome Scan Results OAR6 MRR Effects 0.47 (0.12)

  14. Genome Scan Results OAR7 MRM Effects 0.91 (0.23)

  15. Mode of inheritance • Effects similar in male and female progeny • MRM differs from MRR • If single gene trait then • Allele frequencies differ in M and R • Dominance ≠ 0 • No imprinting • Epistatic • Allele frequencies differ in M and R

  16. Comparative mapping • SSC8 OAR6 • Cassady et al. (2001) • King et al. (2003) • SSC7q OAR7 • Bidanel et al. (2000) • Wada et al. (2000)

  17. Future Prospects • Additional genotyping in this experiment? • Comparative genomics – candidate genes • Phenotyping in other sheep QTL experiments • Phenotyping flocks which test for Booroola (OAR6)

  18. Conclusions • Evidence for QTL affecting teat number • OAR6 ** • OAR7 * • Potential to introgress into prolific strains • Improve mothering of triplet+ litters

  19. Thanks to … • Coauthors • Hannah Henry • Anne Beattie • Grant Montgomery • Staff at Woodlands and Tara Hills research stations • Invermay wool group

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