Map-based quantitative trait locus identification

Poultry gene mappers chose microsatellites as the main source of genetic markers for poultry genome mapping, similar to the marker type used for other farm animals, laboratory animals, and humans. Optimal strategies for applying DNA markers in poultry populations are discussed, including the number of markers to be used, genome representation, population structure, choice of markers, population size, statistical stringency for association between markers and quantitative trait loci (QTL), and biological verification of a linkage. It is shown that an efficient strategy should be based on a combination of a low stringent statistical test for the existence of linkage between a marker and QTL and an appropriate genetic test for the discrimination between true and false linkage. The source of the genetic variation to be used is discussed and, as an illustration, three types of resource populations are presented. The informativeness of different matings using various genotypes of the parents are considered and it appears that selection of markers based on the heterozygosity of the sire is the most efficient marker screening approach.