Analysis Of Genetic Diversity And Evaluation Of Growth Performance Of Three Red Tilapia Populations

Red tilapia is a good breed which has good taste,was welcomed by more and more fish farmers and consumers in China.Freshwater Fisheries Research Center(FFRC)of the Chinese Academy of Fishery Sciences has long history in tilapia breeding and aquaculture.There were three populations of red tilapia was introduced into FFRC,i.e.Malaysia population in 2009 from Malaysia,and red tilapias of Taiwanese and Israel from Fujian province of China in 2014.In this study,the genetic diversity and structures of the three populations of red tilapia were studied from their morphological characteristics and molecular biology,and compared growth performance of F1 generations of three red tilapia populations using a complete diallel mating system.Firstly,the morphometric differences among populations of Taiwanese red tilapia,Israeli red tilapia and Malaysian red tilapia were studied with one-way ANOVA,cluster analysis and principal component analysis.Regression analysis was used to compare the impacts of morphological traits on body-weight among three populations of red tilapia and establish the multiple regression equations.The result showed that morphological characters were rather similar between Israeli red tilapia population and Malaysian red tilapia population,while Taiwanese red tilapia population showed differences.Three principal components were constructed of which the contributory ratio,from high to low,were 34.8%,16.7%and 13.0%,summing up to 64.5%.The results of multi-variant indicated that there were some morphological differences among the three populations of red tilapia and the indicator of morphological traits were total length,body depth,head length,snout length and caudal peduncle depth.Secondly,180 genotyped individuals from three populations of red tilapia,i.e.Taiwan,Israel and Malaysia population,were studied by using fourteen microsatellite markers.The results showed that all microsatellite loci were detected with highly polymorphic,with mean number of alleles,expected and observed heterozygosities,polymorphic information content of 14.87,0.72,0.75,0.72,respectively.All populations presented high levels of heterozygosity and the populations of Taiwan and Israel showed higher heterozygosity than Malaysia.F-statistics analysis showed that there was no significant genetic differentiation between the populations of Taiwan and Israel(P>0.05),whereas indicated remarkably significant genetic divergence in other pairs(P<0.01),suggesting the populations of Taiwan and Israel in relationship were near with each other while they were far with Malaysia.This result was accordance with the result showed in un-weighted pair group methods with arithmetic tree based on Nei's genetic distance.Similar result was revealed via a Bayesian STRUCTURE analysis,which indicated that Taiwan and Israel populations were obviously different from population Malaysia.Analysis of molecular variances revealed that the genetic variation among populations explained significantly 8.7%of the total variance.Finally,using a complete diallel mating system,growth and hybrid vigour among three populations of red tilapia were compared.The study showed that the F1 generations of Taiwanese(?)and Malaysia(?)had faster growing rate and more uniform size than others with the average growing rate of 3.07,instantaneous growing rate of 0.04 and the weight coefficient of variation of 0.24.The F1 generations of Taiwanese(?)and Malaysia(?)grown faster than their parents and other crossbred F1 generations.The study showed that there were morphological differences and genetic differentiation between different populations of red tilapia.We could get improved growth traits using a mating system and provide practical basis for the research of red tilapia's genetic improvement.