Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

QTL for nematode resistance traits in the Blackface population

We aimed to identify quantitative trait loci associated with endoparasitic infection in Scottish Blackface sheep. Data was collected from 789 animals over a 3-year period. All of the animals were continually exposed to a mixed nematode infection by grazing. Faecal samples were collected in August, September and October each year at ca. 16, 20 and 24 weeks of age; Nematodirus spp. eggs were counted separately from the other species of nematodes. Blood samples were collected in October from which IgA activity was measured and DNA was extracted for genotyping. 139 Microsatellite markers were genotyped across 8 chromosomal regions (chromosomes 1, 2, 3, 5, 14, 18, 20 and 21) in the sires and progeny were genotyped for the markers that were polymorphic in their sire. Evidence was found for QTL on chromosomes 2, 3, 14 and 20. QTL associated with specific IgA activity were identified in chromosomes 3 and 20, in regions close to IFNG (chromosome 3) and the MHC (chromosome 20). QTL associated with Nematodirus FEC were identified on chromosomes 2, 3 and14. Lastly, QTL associated with non-Nematodirus Strongyle FEC were identified on chromosomes 3 and 20. This study has shown that some aspects of host resistance to gastrointestinal parasites are under strong genetic control, therefore these QTL could be utilised in a marker assisted selection scheme to increase host resistance to gastrointestinal parasites.

Compared to previously publisged data, these are the strongest QTL yet dected for nematode resistance.

Exploitation of these results is desirable and conceptually straightforward - they need to be verified in independent populations (preferably commercial sheep), with animals containing haploytpes associated with increased resistance then preferentially used by the breeders. We are currently in this phase: we have collected blood and FEC samples from commercial sheep of known parentage, we are developing marker panels using previosuly described results from GeneSheepSafety, and we will genotype these phenotyped animals. Results will be fed back to farmers, who will then have the opportunity to utilise animals with the most favourable resistance genotypes.

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Reported by

Roslin Institute
EH25 9PS Midlothian
United Kingdom