The Salt Tolerance Domestication And Genetic Variation Among The Gili Tilapia (Oreochroms Niloticus♀×sarotherodon Melanotheron♂) And Their Two Parents

Tilapia generic perciformes cichlidae, native to Africa and the Middle East, currently isone of the most important aquaculture fish in the world, is also a typical euryhaline fish. Niletilapia grows fast, salt tolerance ability in general; Salol tilapia salt-tolerant ability strong, butgrew more slowly. Angelique tilapia growth speed and salt resistance between two parents,both maternal Nile tilapia growth speed, and male parent salol tilapia salt-tolerant abilitystrong characteristic, thus for angelique tilapia genetics, molecular genetics and evolution ofmany scholars have become interested in the subject. This paper angelique tilapia and the salttolerance of domesticated differences between the parent and the study of genetic variation isdesigned to explore the Nile tilapia and salol tilapia two parent’s contribution to the offspringgrowth, resistance to salt, for angelique further cultivation of tilapia and screening to lay atheoretical foundation.1. Establishment and Orthogonal Optimization of SSR-PCR Reaction System for TilapiaThe total DNA of tilapia was extracted by using“phenol-chloroform extraction method”，The results showed that the concentration, purity and integrity of total DNA are all well byagarose gel electrophoresis and ultraviolet spectrophotometry. In this test，the orthogonaldesign L9（33）was used to optimize the SSR-PCR amplification system of tilapia in threefactors (the concentration of Taq DNA polymerase，SSR primers and Template DNA)．Theoptimized PCR reaction system of tilapia SSR marker with a total volume of25μL:10×Buffer2.5μL，2.5mmol/L dNTPs2μL，10μmol/L1.5μL of each SSR prime，Taq enzyme0.2μL(5U/μL)，100ng/μL Template DNA0.5μL，ddH2O17.3μL.The optimized reaction system wasof good reproducibility,stable and reliable amplification results.This research built the solidfoundation for the further study of tilapia SSR marker. 2. Effects to salt tolerance of GILI tilapia and its two parents in the chronic salinity stressexperimentIn order to further study salt tolerance performance of a hybrid by Oreochromisniloticus(♀)×Sarotherodon melanotheron(♂)which had been examined and approved byChina National Aquaculture Variety Approval Committee as a new variety for aquaculture andnamed as“GILI tilapia”in2009, researches have been carried out to study the salt tolerance inthe chronic salinity stress experiment to GILI tilapia and its two Parents, the differences ofsalt tolerance performance of three kinds of tilapia are analysised, and the regression modelbetween mortality of salt tolerance in the chronic salinity stress and death of time, death ofsalinity are established, the results of the study show that:(1) There are significantdifferences in capacity of salt tolerance among three kinds of tilapia, the performance of salttolerance of GILI tilapia is close to S.melanotheron, it is much more than O.niloticus, theaverage death salinity of three kinds of tilapia when they domesticate in salt are57.9,66.7and18.5respective.(2)There are the most differences of death time domesticated amongindividuals in O.niloticus, it is the least in S.melanotheron, it is medium in GILI tilapia. Thereare the most significant normal negative deviation in GILI tilapia and S.melanotheron, Thereare the more values of outlier and extremum, O.niloticus has a significant normal positivedeviation, it has outlier values, no extremum values.(3) The regression relationship betweenthe mortality of chronic salinity stress to salt and the death time, death salinity of three kindsof tilapia are fit for single-element regression model, the single-element regression modelbetween the salt tolerance mortality (Y) and the domestication time of death (t) and salinity ofdeath (s) of GILI tilapia are growth modelY=e(7.694+0.031t)(R~2=0.979)and quadratic modelY=0.542-0.037s+0.001s~2(R~2=0.950)respective.3. The genetic variation analysis of microsatellite among the Gili tilapia and their two parents Gili tilapia which had been examined and approved by China National AquacultureVariety Approval Committee as a new variety for aquaculture in2009, it was a F2hybridoffspring by Oreochromis niloticus(♀)×Sarotherodon melanotheron(♂), Sarotherodonmelanotheron had stronger salt-tolerance and Oreochroms niloticus had faster growth rate. Inorder to analyze genetic characteristics of Gili tilapia and its two parents,6pairs ofmicrosatellite primers were chosen, the results were as follows:（1）The size range ofamplified products of six pairs of microsatellite primers was180~350bp, and21alleles werefound, there were highly significant difference among the groups, microsatellite loci andalleles.（2）The value of population genetic diversity indicators of effective number of alleles(Ne), Nei’s gene diversity index (H) and polymorphic information content (PIC) were Gilitilapia>Oreochroms niloticus>Sarotherodon melanotheron, the Gili tilapia was highlypolymorphic, its PIC value was0.657.（3）The genetic distance between Gili tilapia andSarotherodon melanotheron was more close than it’s between Gili tilapia and Oreochromsniloticus, Sarotherodon melanotheron had more effect on Gili tilapia than Oreochromsniloticus.4. Correlation analysis of microsatellite DNA marks with salt tolerance traits of GilitilapiaThe SPSS13.0was used to analyze the effect of these43microsatellites on salt-tolerantproperties of tilapia. In43microsatellite seats, there are five seats were significantlyassociated with salt tolerance traits, respectively is the tag UNH914, UNH848, PRL2, PRL3,UNH222, including UNH848reached extremely significant level (P <0.01).