Genomics and quantitative genetics

The interaction between genomics and quantitative genetics has been a two-way street. Genomics contributed genetic markers and genetic maps making it possible to study quantitative trait loci (QTLs), and quantitative genetics contributed new theories and computational techniques to deal with the data generated by QTL studies. QTL studies in forest trees have led to the discovery of a few major genes masquerading as quantitative genes, such as genes for rust resistance in several pine species. QTLs for many traits including height growth, leaf traits, wood specific gravity, flowering, frost resistance, disease resistance, and ease of vegetative propagation were found in one or more species. Spring cold hardiness in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) holds the record for number of QTLs with 14. Generally the number is under seven. The effects are often large, but this may often be due to small population sizes. At this time the impact on forest tree breeding is small, although the potential is certainly there. An interesting marker aided back-crossing program is underway in American chestnut (Castanea dentata (Marsh.) Borkh.).