Ideotype Development in Southern Pines: Rationale and Strategies for Overcoming Scale-Related Obstacles

Indirect genetic selection for early growth and disease resistance of southern pines has proven remarkably successful over the past several decades. However, several benefits could be derived for southern pine breeding programs by incorporating ideotypes, conceptual models which explicitly describe plant phenotypic characteristics that are hypothesized to produce greater yield. The potential benefits of using ideotypes include improvement in trait heritabilities and genetic correla- tions, higher genetic gain in diverse silvicultural environments, guidance for developing mating designs, and provision of a framework for synthesis of tree production physiology knowledge. There are numerous obstacles to the development of ideotypes for southern pines, most of them related to the difficulty of linking traits and processes that operate at small spatial and temporal scales (e.g., tree crown morphological traits or leaf net photosynthesis) with outputs that occur at large spatial and temporal scales (e.g., stand-level, rotation-age stem biomass yield). Fortunately, as we enter the 21st century, several relevant advances are converging that bode well for overcoming these obstacles. These advances relate to improvements and developments of process modeling, advances in technologies that permit measures of component processes at relevant scales, the likely future importance of intensive clonal forestry, and the movement toward large-scale genetic block plot experiments. FOR. SCI. 47(1):21-28.