Analysis of the diversity of some French breeds and lines of pigs using genetic markers in the framework of a wide European survey

A sample of sixteen French breeds (and lines) of pigs was investigated in the framework of an EU-funded diversity project including seventy breeds, about fifty individuals per breed having been individually examined. The French sample was made of five local breeds, four French varieties of major international breeds such as Large White, Landrace, and Piétrain, and seven commercial lines either purebred or synthetic. The genetic markers were microsatellites (50 loci) and AFLP (148 loci), the latter being a length polymorphism of amplified DNA fragments. A large within-breed variability was observed in microsatellites. The average within-breed expected heterozygosity (0.56) and number of alleles per locus (4.6) in the French breeds were close to the European averages. The phylogenetic tree drawn from the Reynolds distances among the seventy breeds showed that the national varieties of major breeds and the commercial lines were mostly clustered around their breeds of reference (Large White, Landrace, Piétrain, Duroc and Hampshire). The French breeds and lines clustered in accordance with expectation. The analysis of diversity showed that the local breeds accounted for 56 % of the total European microsatellite diversity, and slightly less for AFLP. The genetic originality of the French local breeds, particularly Basque and Limousin, confirmed the pilot study of LAVAL et al (2000). The important diversity contribution of the Tia Meslan synthetic line was noted, this line being known to be hosting genes from two Chinese breeds. The paper discusses what can be learned from this study and applied to the conservation of breeds and management of genetic variability in the pig, around the central question which is to know to what extent the marker diversity reflects some useful genetic variability.