The Genetic Parameter Estimates On WSSV Resistance And Genetic Diversity Analysis In Wild And Selected Populations Of F.chinensis Based On SSR Marker

Fenneropenaeus chinensis was one of the most important fishery resources and mariculture species in China,however,WSSV(White Spot Syndrome Virus)disease seriously interfere with the development of shrimp framing industry.Genetic diversity is the key to organisms adapt to the environment and high genetic variation of population is also the basis for genetic breeding.Whether successive generation's artificial breeding would reduce the genetic diversity and affect breeding effects of F.chinensis remains to be verified by experimental data.SSR could be used to genotype offspring and calculate paired molecular correlation among individuals.In this study,physical pedigree(PR)and molecular correlation(MR)were used to estimate the heritability of survival time after WSSV challenge and cross validation was used to predict the predicting ability and accuracy of MR and PR.A new method is expected to be applied to estimate genetic parameter in F.chinensis.Main results of this study were summarized as follows:1.SSR analysis on genetic diversity in breeding and wild populations of Fenneropenaeus chinensis.The results showed that a total of 462 alleles were identified at 15 microsatellite loci in the two populations,the numbers of alleles(Na)and effective alleles(Ne)were 3-44 and 2-29,respectively.The Polymorphism Information Content(PIC)ranged from 0.518 to 0.964,and the observed heterozygosity(Ho)values of WP and BP were 0.518 and 0.964,respectively,allele frequency of 15 loci in two populations changed significantly.P-values were calculated to confirm whether the 15 loci deviated from the Hardy-Weinberg equilibrium or not.Of the 30 population loci,there were 11 population loci was Heterozygote excess.The Shannon genetic diversity index(H)in WP and BP were 2.786 and 2.399,respectively.The Nei's unbiased genetic Distance(u D),as well as unbiased genetic Identity(u I)was 0.17 and 0.838,respectively.The Gene Flow(Nm) and Fst value of the two populations were 17.997 and 0.017(P=0.001),respectively,indicating a low level of genetic differentiation.Partitioning of the genetic variation revealed that only 7.50% of the genetic variation was from among the populations,and the other genetic variation was from within the populations.All the results showed that the “Huanghai No.2” breeding population after 10 generation's successive selective breeding was still high in genetic diversity and had the potential to be used for further study as breeding materials.2.Using pedigree to estimate the genetic parameters of WSSV resistance trait of “Huanghai No.2” Fenneropenaeus chinensis.A total of 4302 individuals from 181 families bred in 2015 and 2016 were used to WSSV oral infection.Combination Animal Model and Restricted Maximum Likelihood Method were used to estimate the heritability and genetic progress of WSSV resistance trait in F.chinensis.The results showed that the heritability of WSSV resistance trait in F.chinensis was 0.012±0.022,the common environmental effect was 0.04±0.01.The predictive genetic increment was 0.036,the predictive genetic progress was 0.017%,and the real genetic increment was-137.84.These results could be used to provide reference for genetic breeding of F.chinensis for WSSV resistance.3.Using molecular correlation to estimate the heritability of WSSV resistance trait of “Huanghai No.2” Fenneropenaeus chinensis.A total of 670 samples from 67 families were used to genotype.Fifteen paires of fluorescence labeled microsatellite primers were used to genotype.Molecular correlation and pedigree were used to construct additive genetic correlation matrix to estimate the heritability of WSSV resistance trait.Finally,the cross validation was used to test the predicting ability and accuracy of PR and MR.The results showed that Pearson Correlation Coefficient of the molecular correlation and pedigree was 0.414.According to the same animal model and Restricted Maximum Likelihood Method,the results based on molecular correlation and pedigree to estimate heritability of F.chinensis were 0.064±0.048 and 0.050±0.0439,respectively.Cross validation results show that the Pearson Correlation between observed and predicted value based on molecular correlation and pedigree were 0.7277 and 0.7270,and the accuracy were 0.8530 and 0.8526,respectively.The results mentioned above showed that molecular correlation is one of the effective methods to estimate genetic parameters of F.chinensis.