ABSTRACT
Genetic mapping is the ordering of specifi c genes or DNA fragments (genetic markers) along a chromosome, based up observed frequencies of recombination in pedigrees. It provides the approximate locations of these
1 Department of Forest Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada; e-mail: kermit.ritland@ubc.ca 2 Department of Ecosystem Science and Management, Texas A&M University, College Station, Texas 77843-2138, USA; e-mail: k-krutovsky@tamu.edu 3Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan; e-mail: ytsumu@ffpri.affrc.go.jp 4Natural Resources Canada, Canadian Forest Service, Laurentian Forestry Centre, 1055 du P.E.P.S., P.O. Box 10380, Stn Sainte-Foy, Québec, Québec G1V 4C7, Canada; ae-mail: betty.pelgas@RNCan-NRCan.gc.ca be-mail: nisabel@cfl .forestry.ca 5Canada Research Chair in Forest and Environmental Genomics, Centre d’étude de la forêt, Université Laval, Québec, Québec G1V 0A6, Canada; e-mail: jean.bousquet@sbf.ulaval.ca *Corresponding author
entities, which can serve as DNA “landmarks” for further studies (Ott 1999). Physical mapping, in contrast, uses various molecular techniques to reassemble the actual DNA into contiguous stretches, such that numbers of bases separating genes are approximately known, as in for example the chloroplast genome (Tsumura et al. 1993) and the nuclear genome (Amarasinghe and Carlson 1998). Quantitative trait loci (QTL) mapping places the locations of putative genes underlying a quantitative trait onto a genetic map (Lander and Botstein 1989). Conifers have enormous genomes, on the order of tens of billions of nucleotides (Murray 1998). This prohibits physical mapping, and suggests that marker/QTL mapping may continue to dominate conifer genetics research (Neale et al. 1994; White et al. 2007). In addition, the conserved nature of conifer evolution places greater importance on comparing genetic and QTL maps (comparative mapping) in conifers (Krutovsky et al. 2004) and transferring information among these species.
