This study investigates the benefit of including information on an identified major gene in the estimation of breeding values in BLUP selection programmes. Selection for a quantitative trait is controlled by polygenes and a major locus with known effect. The benefit of using the gene information obtained in the short-term was maintained in the long-term by applying a selection tool which makes use of BLUP evaluation and optimisation of genetic contributions for maximising genetic gain while

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... ricting the rate of inbreeding. In the mixed inheritance model the selection tool, initially proposed for an infinitesimal model, was able to restrict the rate of inbreeding to the desired value and to give higher rates of response than standard truncation selection both when using and ignoring the information on the major gene. The simple use of BLUP (standard truncation selection) allowed long-term benefits from using the gene in situations where the favourable allele was recessive or additive with large effect. © Inra/Elsevier, Paris major gene / optimal selection / BLUP selection / restricted inbreeding Résumé -Bénéfice possible de l'utilisation d'un gène majeur identifié dans une évaluation BLUP lors d'une sélection par troncature ou optimisée. Cette étude analyse le bénéfice pour la sélection, d'inclure l'information relative à un gène majeur identifié, dans l'estimation des valeurs génétiques par BLUP. La sélection porte sur un caractère quantitatif contrôlé par des polygènes et un locus majeur Recent developments in selection algorithms using BLUP breeding values allow the optimisation of selection decisions for giving maximum genetic gain over several generations of selection while restricting the rate of inbreeding to specific values [10, 14] . These procedures, initially proposed for the infinitesimal model, are very useful when comparing the efficiency of different schemes (at the same level of inbreeding) in the long-term.