MARKER ASSISTED SELECTION IN FOREST TREES : PERSPECTIVE OPEN BY QTLS DETECTED IN MATING DESIGN

¹ Amélioration, Génétique et Physiologie forestièresINRA - Centre d'OrléansBP 20619 ARDONF-45166 OLIVET CedexFRANCE

² Laboratoire de Biologie ForestièreUniversité Nancy-IBP 239F-54506 VANDOEUVRE-LES-NANCYFRANCE

Marker-assisted selection is not yet very developed in forest tree species in spite of its very obvious application for early selection. In fact, breeders try to maintain a large genetic variation within improved varieties in order to preserve a large adaptive potential, because of the future environmental variations (climate, diseases...). QTL detection in a single family and the subsequent marker-assisted selection in the tested family is thus not of great help. Moreover only a part of the QTLs controlling a trait can be detected in a single family. Many parents should be considered in order to detect most QTLs of a trait. Analysis of a mating design takes care of the genetic variation among parents and allows to assess the heritability of the trait. We have carried out the analysis of such plant material and limited the genotyping activity for QTL detection: parent genotypes are determined at many marker loci on the basis of a genetic map, the QTLs suspected from relationships between familial performances and familial allelic frequencies of the markers deduced from the parental genotypes, are then verified at the individual level in the families segregating for the marker. QTLs have been detected by this way for various traits like growth and wood quality in a 12 x 12 factorial mating of larch. An marker-assisted selection scheme suitable for individual selection in the breeding population will be presented and discussed. It allows selection of parents planted in seed orchards with taking care of the possible interactions between traits.