A GENETIC-LINKAGE MAP OF A CICHLID FISH, THE TILAPIA (OREOCHROMIS-NILOTICUS)

We have constructed a genetic map for a tilapia, Oreochromis niloticus using DNA markers. The segregation of 62 microsatellite and 112 anony mous fragment length polymorphisms (AFLPs) was studied in 41 haploid e mbryos derived from a single female. We have identified linkages among 162 (93.1%) of these markers. 95% of the microsatellites and 92% of t he AFLPs were linked in the final map. The map spans 704 Kosambi cM in 30 linkage groups covering the 22 chromosomes of this species. Twenty -four of these linkage groups contain at least one microsatellite poly morphism. From the number of markers 15 or fewer cM apart, we estimate a total map length of similar to 1000-1200 cM. High levels of interfe rence are observed, consistent with measurements in other fish species . This map is a starting point for the mapping of single loci and quan titative traits in cichlid fishes.