Polymorphic microsatellite differences among four cultured populations of two selected tilapia strains

Abstract

AbstractGenetic diversity plays a vital role for maintainingeconomically important traits in fish populations.The goal of this study was to assess the geneticvariability among four tilapia populations in China.Two populations named XA (Oreochromis aureus,30 samples) and AN (Egyptian Oreochromis niloticus,24 samples) were gathered from Freshwater Fish-eries Research Center (FFRC), and the other twonamed AL (O. aureus, 30 samples) and AJ (Egyp-tian O. niloticus, 30 samples) were from GuangxiFisheries Research Institute (GFRI). GFRI intro-duced AL and AJ from XA and AN, and selectedthem for generations. We want to know if AL andAJ have genetic changes after selection and gener-ations. Fifteen polymorphic microsatellite markerswere used. Our results indicated that the four tila-pia populations showed moderate genetic variabil-ity. The polymorphism information content (PIC)of the four populations was from 0.28 to 0.39; A e was from 1.67 to 2.15; the H e was from 0.35 to0.46; the genetic similarity indexes were from 0.94to 0.69 and also the clustering result showed thatthese four populations were highly related. Therewere no significant changes in genetic variationbetween late-introduced population and early-introduced population of O. aureus. Our resultshelped to understand the genetic variability of tila-pia populations in China and for future marker-assisted selection for important economic traits.Keywords: microsatellite, Nile tilapia, Blue tila-pia, heterozygosity, genetic diversity, selection,loss of genetic variationIntroductionTilapia belongs to Perciformes Cichlida and it isnative to Africa and Middle East. Tilapia (Oreochr-omis mossambicus) was introduced to China in theearly 1950s. Later, many species and strains (Or-eochromis niloticus, Oreochromis aureus, etc.) wereintroduced to China too (Li 2001; Li & Li 2001;Ye 2008). After their introduction to China, tila-pia has been undergone artificial selection forvarious economically important traits, such asfast growth, resistance to environmental stressorsand high percentage of males. Since the expandedproduction of tilapia started, China has been thelargest supplier of tilapia in the world till now(Li, Li, Tang & Cai 2009).Fresh Water Fisheries Research Center (FFRC) isthe most famous genetic and breeding resourcesCenter of Tilapia in China well known as the bestquality of purebred Tilapia parents. And now,FFRC was the head of China Agriculture Techni-que System-tilapia (CARS). The Blue tilapia(O. aureus, XA) was introduced from Auburn Uni-versity by FFRC in 1983, and they have selectedand bred a new Blue tilapia strain, named “Xia’ao1”. This strain is widely used for cross-breedingwith Nile tilapia to get all male tilapia fry inChina. The Nile tilapia samples (AN) used in thisstudy were introduced from Central laboratory forAquaculture Research, Abbassa, Ministry of Agri-culture and Land Reclamation of Egypt by FFRC in1999. Guangxi Fisheries Research Institute (GFRI)was the most famous tilapia fry productive unit inChina as the high male rate of cross-bred tilapiafry. GFRI introduced two strains of tilapia: XA(O. aureus) and AN (Egyptian O. niloticus) from