Genetic diversity of eleven European pig breeds

Abstract

-A set of eleven pig breeds originating from six European countries, and including a small sample of wild pigs, was chosen for this study of genetic diversity. Diversity was evaluated on the basis of 18 microsatellite markers typed over a total of 483 DNA samples collected. Average breed heterozygosity varied from 0.35 to 0.60. Genotypic frequencies generally agreed with Hardy-Weinberg expectations, apart from the German Landrace and Schwäbisch-Hällisches breeds, which showed significantly reduced heterozygosity. Breed differentiation was significant as shown by the high among-breed fixation index (overall F ST = 0.27), and confirmed by the clustering based on the genetic distances between individuals, which grouped essentially all individuals in 11 clusters corresponding to the 11 breeds. The genetic distances between breeds were first used to construct phylogenetic trees. The trees indicated that a genetic drift model might explain the divergence of the two German * Correspondence and reprints E-mail: glaval@toulouse.inra.fr 188 G. Laval et al.breeds, but no reliable phylogeny could be inferred among the remaining breeds. The same distances were also used to measure the global diversity of the set of breeds considered, and to evaluate the marginal loss of diversity attached to each breed. In that respect, the French Basque breed appeared to be the most "unique" in the set considered. This study, which remains to be extended to a larger set of European breeds, indicates that using genetic distances between breeds of farm animals in a classical taxonomic approach may not give clear resolution, but points to their usefulness in a prospective evaluation of diversity.genetic diversity / molecular marker / conservation / pig / European breed Résumé -Diversité génétique de onze races porcines européennes. Un ensemble de onze races porcines en provenance de six pays européens, et incluant un petit echantillon de sangliers, aété choisi pour uneétude de diversité génétique. Cette diversité aétéévaluée sur la base de 18 marqueurs microsatellites typés sur un total de 483échantillons d'ADN. Les racesétudiées manifestent un taux d'hétérozygotie allant de 0,35à 0,60. Les locus sont enéquililibre de Hardy-Weinbergà l'exception du cas des races allemandes Landrace et Schwäbisch-Hällisches, qui manifestent un déficit d'hétérozygotes. L'indice de différenciation entre races estélevé (F ST global de 0,27) et les distances génétiques entre individus permettent de les regrouper pratiquement en 11 ensembles distincts, correspondant aux 11 races considérées. Les distances génétiques entre races ont d'abordété utilisées pour construire des arbres phylogénétiques. Ces arbres suggèrent qu'un modèle de dérive génétique pourrait expliquer la divergence des deux races allemandes, mais aucune phylogénie fiable n'a puêtreétablie entre les races restantes. Les mêmes distances ont ensuiteété utilisées pour mesurer la diversité génétique globale de l'ensemble etévaluer la perte marginale de diversité associéeà chacune des racesétudiée...

Measuring genetic distances between breeds: use of some distances in various short term evolution models

“…Twenty genetically independent loci were considered, a number frequently found in diversity studies [33,37,40].…”

“…Therefore, a high level of polymorphism can be maintained within relatively small samples. The within breed average heterozygosity is generally higher than 0.5 [37,40,54] with extreme values above 0.8 observed for several loci [33]. For a large proportion of microsatellites, the number of alleles observed across mammalian populations can vary between less than 10 to 20 and can be even higher across natural populations of fish [56].…”

Biodiversity of pig breeds from China and Europe estimated from pooled DNA samples: differences in microsatellite variation between two areas of domestication

“…A comprehensive, global assessment of pig diversity would give better insight into the genetic relationships and distinctiveness of pigs from different parts of the world, and may aid in preservation of worldwide livestock diversity. Recent papers have reported on relations between pigs using microsatellite markers [12,22,26,28,40,47,50], but mainly between pig breeds from either China or Europe. For instance, Zhang et al [50] concluded that a number of major groups could be discerned, in part congruent with previous classification schemes.…”

Review: Towards the agroecological management of ruminants, pigs and poultry through the development of sustainable breeding programmes. II. Breeding strategies

“…In France, a few local farms rely on raising local pig breeds linked to specific production systems that associated with typical products with high added value. France is the main 'reservoir' of swine genetic diversity at the European level, with the preservation of six local breeds (Laval et al, 2000). These breeds are generally characterized by low prolificity, high adiposity and low growth, but much higher meat quality.…”