ABSTRACT
Compared to food crops, forest tree improvement is in its infancy. Innate features of trees provide major barriers to breeding progress, most signifi cant of which is the lengthy juvenile phase of 5 to 20 years before they are developmentally capable of fl owering. The long delay in fl owering and typically high genetic load of trees makes it infeasible to use advanced methods such as inbreeding and introgression of rare or exotic alleles. The net result is a very slow rate of domestication for all breeding goals. Transgenic approaches can potentially advance tree domestication, but concerns over the dispersal of transgenic pollen or seed, in addition to a number of other social and technical factors, have prevented most commercial uses of transgenic forest trees in the world (Brunner et al. 2007). Thus, understanding the factors that regulate tree fl owering and discovering ways to manipulate it could enhance tree improvement by speeding breeding and research to develop effective means for genetic containment. Moreover, because fl owering time is an adaptive trait that is affected by global warming (Fitter and Fitter 2002), discovery of the genes important for control of tree fl owering might also aid in the development of strategies for maintaining healthy forest tree populations in the world with rapidly changing climates.
