Genomic and physiological approaches to advancing forest tree improvement.

The recent completion of a draft sequence of the poplar (Populus trichocarpa Torr. & Gray ex Brayshaw) genome has advanced forest tree genetics to an unprecedented level. A "parts list" for a forest tree has been produced, opening up new opportunities for dissecting the interworkings of tree growth and development. In the relatively near future we can anticipate additional reference genome sequences, including the much larger Pinus genome. One goal is to use this information to define the genomic attributes that affect the phenotypic performances of trees growing in various environments. A first step is the definition of ideotypes that constitute optimal tree and stand-level performance. Following this, the genome can be systematically searched for genetic elements and their allelic variants that affect the specified traits. Knowledge of these alleles and their effects will facilitate the development of efficient tree improvement programs through genome-guided breeding and genetic engineering and further our mechanistic understanding of trait variation. Improved mechanistic understanding of tree growth and development is needed to develop process models that will allow us to anticipate and manage change in forest ecosystems. Here we consider the development of an ideotype for loblolly pine (Pinus taeda L.) and discuss genomic approaches for studying the component traits that will enable advances in process model development and the genetic improvement of this important conifer.