| The noble scallop(Chlamys nobilis)is an important mariculture shellfish in China.Our research group has been working on the genetic breeding of noble scallop Chlamys nobilis since 2008.In 2015,the noble scallop Chlamys nobilis was bred a new variety called "Nan’ao Golden Scallop"(hereafter referred to as "Nan’ao Golden Scallop"),which has generated great economic benefits.Due to the careless selection of seeds and the mating strategy of more females than males in the process of artificial breeding,after 5 years of artificial breeding,"Nan’ao Golden Scallop" may have a certain degree of inbreeding.What effect can be achieved if the growth traits of "Nan’ao Golden Scallop" are selected and bred? And what degree of genetic diversity does "Nan’ao Golden Scallop" still maintain? To solve these problems,It is necessary to evaluate its germplasm resources to obtain theoretical basis for reference.In this study,two heterogeneous breeding populations(upper selection group and lower selection group)and one control population were selected by population cutting method,and their genetic parameters were evaluated.SSR and InDel molecular markers were used to evaluate the genetic diversity parameters of the three populations,and transcriptomics was used to compare the differential genes of the three populations.The main results are as follows:1.The shell length and genetic parameters of the upper group were not significantly different from those of the control group since 40 days old,while those of the lower group were always significantly smaller than those of the other two groups.The shell length of the lower group was always significantly smaller than that of the upper group,but its genetic parameters were always significantly larger than that of the upper group.Average selection response,realistic heritability and genetic gain were0.183±0.143,0.115±0.009 and 3.271±2.656,respectively.The mean selection response,realistic heritability and genetic gain of the lower selection group were 0.595±0.187,0.298±0.094 and 7.289±3.183,respectively.2.Genetic diversity analysis of SSR markers: 36 alleles,47 alleles and 43 alleles were detected in the upper,lower and control groups,with PIC average values of0.327±0.078,0.331±0.079 and 0.379±0.091,respectively.The mean values of I were0.695±0.215,0.865±0.233 and 0.858±0.217,respectively,indicating that the three populations deviated from the Hardy-Weinberg equilibrium significantly.3.Analysis of genetic diversity of InDel markers: Ne mean of all loci was1.519±0.297.PIC ranged from 0.141 to 0.506 with an average value of 0.274±0.099.I ranged from 0.2146 to 0.963,with an average of 0.525±0.187.Among them,5 loci deviated from genetic equilibrium significantly,and 4 loci had negative genetic deviation index.4.The number of differentially expressed genes among the three populations was less than other study,the total number of differentially expressed genes between the upper and lower groups was 462,and the total number of differentially expressed genes between the upper and lower groups was 603.There were 140 differentially expressed genes with similar expression levels in the intersection of the two differentially expressed groups.87 genes were up-regulated and 53 were down-regulated.A total of6 up-regulated genes related to growth and development were screened.Three of them were related to the regulation of actomyosin composition.One is involved in the regulation of insulin production;One participates in proteolysis;One is associated with calcification of shells.Through the study of the selection of "Nan’ao Golden Scallop" breeding population and to assess its genetic parameters,and the genetic diversity of different molecular marker detection,from various angles to reveal the "Nan’ao Golden Scallop" breeding groups of germplasm,for the protection,development and utilization of germplasm resources and genetic breeding work provides theoretical basis and reference data. |
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