Molecular genetics and developmental physiology: Implications for designing better forest crops

Current tree biology related to tree genetics and breeding has two important developments that have not well been integrated in the literature. The first is the physiological and biochemical dissection of plant yield, whereas the second is the genetic mapping based on molecular markers, such as RFLPs, RAPDs, AFLPs, and microsatellites. Genetic mapping has revolutionized traditional quantitative genetic analysis by which the genetic variation of a character is described in terms of its mean and (co)variance without the knowledge of the underlying genes. By integrating physiological and developmental studies of yield traits, genetic mapping can provide a unique means for detecting key QTL that play important roles in affecting tree growth and metabolism. The incorporation of these QTL into commercial populations through gene transformation or marker-assisted selection will move current breeding programs strictly based on an empirism to an approach that is mechanistically oriented. In this review, we discuss how plant physiology and development are merged with genetic mapping to formulate the strategy of molecular breeding in which superior forest crops are selected at the gene level. It is anticipated that this novel breeding strategy can potentially provide major breakthroughs for tree breeding.