Teaching a new dog old tricks: Identifying quantitative trait loci using lessons from plants

Locating quantitative trait loci (QTL) in mammalian systems has proven diff icult due to the lack of genetic control and reproducibility, as well as th e expense of maintaining sufficiently large populations for genotyping and phenotyping. In plants, populations of recombinant inbred lines (progeny br ed to homozygosity from a single cross) do not have these problems, Methods developed to identify QTL in a recombinant inbred soybean population provi de a basis for analysis of a suitable mammalian population, such as Portugu ese water dogs in the United States. The more than 6,000 dogs have accurate pedigrees, available phenotypic data and samples for genotyping, as well a s interesting quantitative trait variation, The computer program Georgie al lows us to choose large subpopulations with desirable characteristics such as high degrees of consanguinity that capture some of the benefits of recom binant inbred lines in plants, Computer simulations extending methods devel oped for simpler plant populations indicate that QTL with realistic effects can be identified from such subpopulations. Currently we are developing ma rkers and collecting phenotypic and genotypic data from this population to begin the process of unraveling the genetic basis of quantitative traits in dogs.