Over the past decade, several resource populations have been established to detect QTL for traits of economic importance in pigs using breed crosses. Although each population allows independent identification of QTL, each population is often of limited size, which restricts the statistical power and accuracy of QTL identification. A joint analysis of data from multiple projects, which is what will be described here for the Berkshire x Yorkshire cross population at Iowa State University and the Berkshire x Duroc cross population at the University of Illinois, will allow more accurate identification of QTL.

A joint analysis of data from seven F2 crosses from six countries was recently completed by Walling et al. (2000). All crosses were based on a Western commercial breed crossed with either Meishan or European Wild Boar. Data from the three traits that were most similar across populations (birth weight, growth, and backfat) were analyzed to detect QTL on SSC4 using a breed-cross model. Despite considerable differences in the breeds, markers, and traits, this study clearly shows that a joint analysis is feasible and allows for combining the limited power of individual studies. Joint analysis also allows testing additional hypotheses, such as whether QTL from different populations are identical.