Abstract
This chapter describes application of association genetics in forest tree species for the purposes of selection. We use the term gene-assisted selection (GAS) to denote application of marker-trait associations determined via association genetics, which we anticipate will be based on poly morph isms associated with expressed genes. The salient features of forest trees are reviewed, including existing and somewhat limited knowledge of linkage disequilibrium (LD), as well as genomic information for both conifers and hardwoods. The relatively short span of LD in largely undomesticated and outbred forest tree species offer good prospects for precisely locating quantitative trait nucleotide (QTN), but necessitates wise candidate gene selection and generation of nongenic sequences, which could be limiting, particularly for conifers. Prerequisites for successfil application are discussed, and include suitable populations for detecting LD; powerful quantitative genetic and bioinformatic capabilities; large EST libraries, if not whole genomic sequences, to identify candidate genes; and other capabilities for studying functional genomics; as well as a mix of quantitative genetics, tree breeding, and molecular biology skills. Experimental designs for tree improvement applications ire also described, as well as analytical methods. For existing tree improvement practice, GAS should be applicable in virtually all population strata, although careful evaluation on a case-by-case basis will be needed to determine the appropriate implementation pathway(s). Such evaluation will likely include numerical simulation. GAS also fits well with other biotechnologies used for tree improvement. A number of impediments to application are also discussed, including institutional barriers; implementation costs; certain molecular mechanisms underpinning variation; and modes of gene action such as epistasis and genotype-enivirontnent interaction.
Citation
Wilcox, Philip L.; Echt, Craig E.; Burdon, Rowland D. 2007. Gene-assisted selection: applications of association genetics for forest tree breeding. In: Associated Mapping in Plants. 211-247
