-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...

The method described uses monogenic inherited characters as markers by which the transmission of homologous chromosome sections from parents to progeny can be controlled. The procedure then attributes effects on continuously varying characters to marked chromosome sections. It allows the mapping of effects having a share in quantitative characters in natural or breeding populations.

Summary Three informative pig F2 families based on European Wild Boar (W), Meishan (M) and Pietrain (P) crosses have been used for genome‐wide linkage and quantitative trait loci (QTL) analysis. Altogether 129 microsatellites, 56 type I loci and 46 trait definitions (specific to growth, fattening, fat deposition, muscling, meat quality, stress resistance and body conformation) were included in the study. In the linkage maps of M × P, W × P and W × M families, average spacing of markers were 18.4, 19.7 and 18.8 cM, the numbers of informative meioses were 582, 534 and 625, and the total lengths of autosomes measured were 27.3, 26.0 and 26.2 Morgan units, respectively. Maternal maps were on average 1.3 times longer than paternal maps. QTLs contributing more than 3% of F2 phenotypic variance could be identified at p < 0.05 chromosome‐wide level. Differences in the numbers and positions of QTLs were observed between families. Genome‐wide significant QTL effects were mapped for growth and fattening traits on eight chromosomes (1, 2, 4, 13, 14, 17, 18 and X), for fat deposition traits on seven chromosomes (1, 2, 3, 4, 6, 7 and X), for muscling traits on 11 chromosomes (1, 2, 3, 4, 6, 7, 8, 12, 14, 15 and X), for meat quality and stress resistance traits on seven chromosomes (2, 3, 6, 13, 16, 18 and X), and QTLs for body‐conformation traits were detected on 14 chromosomes. Closely correlated traits showed similar QTL profiles within families. Major QTL effects for meat quality and stress resistance traits were found on SSC6 in the interval RYR1‐A1BG in the W × P and M × P families, and could be attributed to segregation of the RYR1 allele T derived from Pietrain, whereas no effect in the corresponding SSC6 interval was found in family W × M, where Wild Boar and Meishan both contributed the RYR1 allele C. QTL positions were mostly similar in two of the three families for body conformation traits and for growth, fattening, fat deposition and muscling traits, especially on SSC4 (interval SW1073‐NGFB). QTLs with large effects were also mapped on SSC7 in the major histocompatibility complex (MHC) (interval CYP21A2‐S0102) and affected body length, weight of head and many other traits. The identification of DNA variants in genes causative for the QTLs requires further fine mapping of QTL intervals and a positional cloning. However, for these subsequent steps, the genome‐wide QTL mapping in F2 families represents an essential starting point and is therefore significant for animal breeding.

-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...

For daughter groups of 15 test bulls, controls of paternity were performed by using blood group factors and biochemical polymorphisms. Data of incorrectly assigned daughters influenced the estimation of breeding values, heritabilities and correlations for milk performance traits. Formulae are given that show the effects of variable misidentification rates on estimation of breeding values, selection intensities, heritabilities, and genetic gains. For example, for milk fat yield, the genetic gains drop at a misidentification rate of 15% between 8.7% (for h2 = .5) and 16.9% (for h2 = .2) below values attained without misidentifications. Consequently, decreasing misidentification rates in progeny of test bulls can be used to diminish the progeny size per test bull for constant genetic gain, to achieve more precise ranking of all or distinct test bulls according to their "true" breeding values and(or) to increase the number of test bulls by using the same amount of test inseminations and the same precision of ranking. Actions to reduce misidentification rates in cattle populations are discussed.