We also investigated the stability of QTLs during the maturation of the trees. For example, we identified QTLs for height growth in different linkage groups across three different developmental stages. This differential QTL expression during the maturation suggests that different loci are likely to be involved in the genetic control of height growth at different ages. Thus, rather than a complete temporal change in QTL expression, it seems that maturation also induces a progressive shift of the genetic control of height growth. If the same metabolic pathways are assumed to be responsible for height growth in both juvenile and more mature developmental stages, our results indicate that different regulatory genes or differential expressions of the same set of regulatory genes could be involved in the genetic control of height growth at different stages of maturation.
Stands extend over more than four million ha.
A breeding program for southwest France started in the early 1960s, using recurrent selection. Genotypes that performed well under current environmental conditions will form the genetic basis for future forest regeneration. Therefore, the genotypes used in the breeding program should be selected under the most likely climatic conditions where the trees will grow in the future. We are currently undertaking a molecular, genetic and physiological analysis of drought responses in maritime pine to better understand the genetic control and physiological processes that determine adaptability of forest trees facing drought.