Advances in molecular biology gave rise to a number of new technologies that held great promise for crop breeding. One of such innovations was the development of molecular markers for tagging genes of interest. Genetic markers are landmarks on a chromosome that assist in genome analysis (Lefebvre et al. 1995). Markers are generally described as “genetic tags” that identify particular locations within a plant’s DNA sequence and are transmitted to the offspring following the laws of inheritance from one generation to the next (Drew 1997). The use of DNA-based markers has allowed researchers to mark genes or chromosome regions that are related to genetic traits such as host plant resistance to pathogens and pests (Drew 1997). Once genetic markers are defi ned, they can be used directly in breeding programs since they allow researchers to predict phenotypes based on the presence or absence of the marker. Alternatively, once genes for particular trait have been identifi ed by genetic marker techniques, they can be cloned. A particular advantage of such techniques is that complex multigenic traits can be analyzed. Mapping techniques can also be used to isolate genes based entirely on their genetic behavior. Once these have been identifi ed, sequenced and cloned, gene transfer techniques can be used to transfer them to other species (Drew 1997).