Thus, this project is aimed at moving from the low resolution mapping of QTLs through the high resolution mapping of these QTLs and towards the identification of the genes involved and the specific molecular variant within the gene causing the genetic variation. As knowledge of the molecular basis of QTL action is limited information produced in this project could have a significant influence of quantitative genetic theory and on future breeding programs. Our strategy is to focus of QTLs with the largest effect in a cross between two genetically divergent breeds - the Mangalica (or Hungarian lard) and the Duroc which is renowned for its meat quality - in order to maximize our precision in mapping the QTLs and hence our chance of ultimately cloning one or more of them. We will largely use the positional candidate gene approach, and having mapped the QTLs with high precision we will map candidate genes to the region from an adipose tissue cDNA library as well as mapping potential candidate genes which should map to the region on the basis of their map positions in other species, particularly man and the mouse. Strong candidates (on the basis of position and function) for the QTL effects in the pig will be explored thoroughly.
The project objectives are fully consistent with area 9.1 on "Genome mapping and improvement of farm animal selection" in the INCO COPERNICUS work program as they concern the use of established genetic maps for QTL analysis in relation to improving the quality of production.
This project concerns the mapping of genes of economic importance in pigs and in particular those genes influencing fatness. Reduced carcass fatness brings benefits in both improved carcass quality and efficiency of production. However, reducing overall fatness also reduces the level of fat within the muscle (intramuscular fat), which may reduce the quality of the meat. Identification of genetic markers linked to separate genes controlling total and intramuscular fat would be a major step-forward, enabling animal breeders to select for the two traits independently though selection on the linked markers. Work within the Pig Gene Mapping Project (PiGMaP - funded under the BRIDGE program of EC Framework III) has resulted in the production of a marker map spanning the porcine genome. These maps can be exploited for detecting genes controlling variation in quantitative traits (quantitative trait loci or QTLs). For example, two of the participants in the current project have already identified regions of chromosome 4 containing QTLs with major effects on growth and total body fatness in a wild boar x Large White cross (Andersson et al., 1994. Science 263:1771). Markers identified in experimental crosses have to be verified in the relevant industry populations and, furthermore, it is preferable to identify the gene itself, as this allows greater selection accuracy, more ready portability to other populations and the prospect of even greater improvements through the enhanced understanding of the genetic control of the trait.
Funding SchemeCSC - Cost-sharing contracts
751 24 Uppsala