ASSOCIATION STUDIES FOR WOOD PROPERTIES IN MARITIME PINE.

¹ UMR BIOGECO 1202, INRA, Equipe de Génétique et Amélioration des Arbres Forestiers, 69 route d'Arcachon, 33612 Cestas Cedex, France

Early marker-assisted selection (MAS) is of particular interest to improve wood quality of forest trees. This trait is usually assess at adult stage and is probably the most time consuming and expensive one to measure in a breeding program. Identification of the underlying genes is a pre-requisite for the deployment of a MAS strategy, and this should be aided by general features of forest trees species like abundant allelic diversities, predominant out-crossing mating systems, and low levels of linkage disequilibrium between genes in natural populations. Although QTL analyses allowed the identification of chromosomal regions involved in the control of quantitative traits and preliminary information on the underlying genes, they were unable to provide forest tree breeders with efficient selection criteria. Alternatively, association studies carried out in natural populations may provide the opportunity to directly link nucleotide diversity of candidate genes with trait variation. Here, we present two association studies between polymorphic sites of 9 wood formation genes and variation of physical and chemical wood properties, which were measured in two experimental designs of maritime pine: a 12*12 half-diallel (591 trees) and a clonal test (185 clones). Significant associations were observed using ANOVA and regression models, highlighting the importance of the cellulose and lignin biosynthesis genes on the genetic control of wood properties. Results from both experiments are compared, and their congruence with previous results obtained from candidate gene mapping, expression analysis and neutrality tests, will be discussed.