Advancements in genetic linkage maps and quantitative trait locations of aquatic farming animals

Many countries have launched genomic studies for aquatic fanning animals since the Agriculture Ministry of America initiated genomic studies for five kinds of aquatic fanning animals in 1997. At the end of 2005, genetic linkage maps of approximately 17 briny or limnetic fanning animals have been published. Of these 17 species, the rainbow trout and the Atlantic salmon have high-density linkage maps with over 1 000 markers, the tilapia, the channel catfish, the black tiger shrimp, the Japanese flounder and the European sea bass have middle-density linkage maps with 400- 1 000 markers; the remaining 10 species, including the Thailand walking catfish, the Chinese Zhikong scallop, the common carp, the Japanese yellowtail amberjack and the American oyster, have low-density linkage maps with less than 400 markers. The framework and development of genetic linkage maps of aquatic fanning animals facilitated QTL mapping associated with interesting economic traits, such as growth, resistance and development. However, QTL mapping was only studied preliminarily in a few species with middle or high density linkage maps, such as salmonids （the rainbow trout, the Atlantic salmon and the Arctic char）, the tilapia, the channel catfish and the Japanese flounder. Genetic linkage maps with higher resolution and fine QTLs mapping are the keys to implementing genetic technology in interesting economic traits and also have the power to successfully carry out molecular marker or gene assistant selection breeding in aquatic fanning animals.