Novel polymorphic microsatellites from Florida red tilapia and cross-species amplification in Mozambique and Nile tilapia

Abstract

Tilapia is the common name for nearly a hundred species of cichlid fish which originated in Africa (El-Sayed 2006). It is one of the most important food fish genera in the world (El-Sayed 2006). A few red tilapia variants have been commonly seen in fish markets. While the genetic background of these varieties is not well documented, their derivation is generally attributed to the crossbreeding between mutant reddish-orange Mozambique tilapia (Oreochromis mossambicus) with other tilapia species like Nile tilapia (O. niloticus) and blue tilapia (O. aureus). Florida red tilapia is thought to be the result of blue tilapia mating with Mozambique tilapia (El-Sayed 2006). In Nile and Mozambique tilapia, microsatellites have been isolated (Kocher et al. 1998; Yue and Orban 2002) and applied in genetic studies (e.g. Kocher et al. 1998), whereas in Florida red tilapia, no microsatellites are available. Preliminary tests of cross-species amplification of 30 microsatellites isolated from Nile and Mozambique tilapia revealed that around 30% of tested microsatellites could not amplify products in red tilapia (Feng Liu and Gen Hua Yue, unpublished data). Therefore, to facilitate a better understanding of the genetic variations in tilapia species, we have isolated 19 polymorphic microsatellites from Florida red tilapia, and characterized them in Nile and Mozambique tilapia. These 19 microsatellites were all polymorphic in Florida red tilapia with an average allele number of 4.90 per locus, and average expected and observed heterozygosities of 0.62 and 0.74 respectively. Fourteen out of the 19 microsatellites amplified polymorphic products in Mozambique tilapia and all 19 amplified in Nile tilapia, respectively. Fourteen out of 19 and 13 out of 15 microsatellites were in HardyWeinberg equilibrium (HWE) in Nile and Mozambique