| Grouper is the most important seawater fish in the world.The scope of farming in our country has gradually developed from coastal cities in the south to Shandong,Tianjin and other places in the north.It has important economic value and has a large market demand.It has received widespread attention from the people,and the end of the 20 th century,researchers have successively carried out artificial propagation and crossbreeding of grouper,breaking the bottleneck of artificial breeding of groupers,and making the grouper fish industry have achieved tremendous development.The purpose of crossbreeding of grouper is to obtain new varieties with the advantages of strong disease resistance,fast growth,and tender meat.In this study,morphological differences were analyzed between Epinephelus moara(?),E.lanceolatus(?)and Yunlong grouper populations of the hybrid offspring,and genetic diversity among populations was analyzed using microsatellite markers at the molecular level f.The genetic diversity and phylogenetic relationship among the populations were analyzed between the grouper and grouper Yunlong spots.The growth traits were compared among the families.The main research line includes the following:(1)Analysis of morphological differences of hybrid Yunlong grouper E.moara(?)and E.lanceolatus(?)E.moara and E.lanceolatus belong to different species of fish and they have obvious differences in their external morphology.Multivariate analysis methods(principal component analysis,cluster analysis,and discriminant analysis)were used to perform statistical analysis on the countable traits of E.moara(?)and E.lanceolatus(?)and their hybrid offspring.The results of the study show that cluster analysis of three grouper populations of E.moara,E.lanceolatus and hybrid offspring was conducted using 19 scale traits.Cluster analysis was performed between the tree and the population.Euclidean distance can be found,Yunlong grouper first with the E.moara(?)grouped together,then with the E.lanceolatus(?)grouped together.In this study,there were six principal components,and the cumulative total variation contribution rate was 74.945%.The differences in morphological differentiation between the three groups were significant,forming three different groups.Yunlong grouper had its own unique morphological features.Yunlong grouper and E.moara have small deviations from each other,and they deviate more from E.lanceolatus.A stepwise discrimination method was used to select the parameters of the length of the kiss/body length,body height/body length,tail stem height/body length,pelvic fin base to anal fin anterior base length/body length from 19 shape ratio parameters.With the discriminant function,the comprehensive discriminant rate was 96.43%,and the Yunlong grouper could be distinguished from the parent,laying a foundation for the germplasm identification of Yunlong grouper.In summary,the morphological characteristics of the Yunlong grouper are biased towards the maternal E.moara,and there were also heterosis.(2)Analysis of genetic characters in E.moara,E.lanceolaus and their hybridsMicrosatellite marker(SSR)was an effective method of analysis of genetic diversity of fish,the genetic variation in E.lanceolatus(?),E.moara(?)and their hybrid progenies Yunlong grouper were studied by using 27 pairs of microsatellite primers from the relative species of Epinephelus.Polymorphism was detected in Yunlong grouper by using 25 of 27 SSR markers.The genetic diversities of three grouper species were analyzed by calculating the effective allele number(Ne),observed heterozygosity`(Ho),expected heterozygosity(He),Shannon index(I),genetic similarity Nei's genetic distance,polymorphism information content(PIC),Overall inbreeding coefficient(Fit),inbreeding coefficient in population(Fis),genetic differentiation coefficient(Fst).The results showed that the average Ne were most in E.moara(2.8926),followed by Yunlong grouper(2.8010),and the smallest in E.lanceolatus(2.0564).The average Ho of E.moara,E.lanceolatus and Yunlong grouper were 0.6046,0.5661 and 0.5010,the average polymorphic information content were 0.5778,0.5446 and 0.3420.The inbreeding coefficient of the 3 populations was 0.1508,and the genetic differentiation coefficient among populations was 0.0677,which indicated that 6.77% of the genetic variation was from intergroup,and 93.23% of the genetic variation came from the differences among individuals in the population.The genetic differentiation coefficient was-0.0722 among the 3 grouper species,and the intergroup population gene flow(Nm)was 2.3963.The cluster analysis diagram constructed by using the UPGMA method showed that the hybrid Yunlong grouper and the female E.moara first clustered together.The results provide the genetic basis for the formation of heterosis traits of Yunlong grouper and the identification of hybrid germplasm at the molecular level.(3)Parentage among the Yunlong grouper and its parents and the quantitative analysis among familiesIn this study,9 pairs of polymorphic microsatellite markers were used to identify the genetic relationship of the hybrid offspring Yunlong grouper and its parents.The results of identification by Cervus 3.0 software showed that the average Na was 15.67,the average PIC was 0.779,the Ho average was 0.888,and He averaged 0.801.When the parental genotype was unknown,the cumulative exclusion rate was 0.9974413,When the genotype of one parent was known,the cumulative exclusion rate was 0.99992718,he parent exclusion probability was 0.99999991.Combined with the LOD value,266 fish were successfully identified in 300 offsprings,and the identification rate was 88.6%.Using SPSS19.0 software and Excel 2013 to identify the offspring for family growth comparisons,the results show that in the number of 4,8,9,18,19,21,22,24 familie number,the average full length and average body weight were significantly better than other families,and with good breeding ability. |
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