| Sinonovacula constricta is one of the four China's aquaculture shellfish,which is widely distributed in coastal areas.Because of germplasm degradation and marine environment pollution,our laboratory has been performing selective breeding to zhejiang yueqing wild group since 2008,under shell length as indicator and 2.063 intensity conditions.In order to evaluate the ability of the selected index to stabilize the offspring,7 half-sib families and 14 full-sib families of razor clam(Sinonovacula constricta)were obtained by the balance nest design in which each male mated with two females.The shell length and shell height of each family were measured on 60 d,90d and 150 d post-hatch.The heritability of the growth straits of the fast-growth selected line of S.constricta was estimated using the full-sib family's theories.Analysis of variance showed that maternal effect existed because that the maternal genetic variance component estimates are all greater than those of paternal ones of each growth trait(P<0.01),So the heritability of paternal half-sib families estimates in the narrow sense were precise unbiased estimator of the fast-growth selected line of S.constricta.The estimates of narrow-senseheritability were 0.298,0.541 and 0.574 for shell length 0.139,0.519 and0.518 for shell height at spat stage,respectively.All of them belonged to moderate heritability,thus showing a high potential for selective breeding.The estimates of genetic correlation coefficients were 0.980,0.755 and0.942,respectively.The estimates of phenotypic correlation coefficients were 0.910,0.882 and 0.912,respectively.The study indicates that shell length or height should respond favorably to direct and indirect selection for the fast-growth selected line of S.constricta at spat stage.Alpha amylase is one of the digestive enzymes in living organisms,which is mainly involved in the metabolism of carbohydrates,and which will provide energy for the maintenance of life,growth and reproduction of living organisms.In order to explore the association between the polymorphism of alpha amylase exon region and growth trait of Sinonovacula constricta,this study detected the polymorphism of the exon of S.constricta alpha amylase gene by DNA sequencing in individuals that have significant difference in growth traits.Eighteen alternative single nucleotide polymorphism(SNP)mutations were identified of the gene,such as Rs-1: 48 G/C,Rs-2: 247 C/A,Rs-3: 420A/G,Rs-4: 441C/T,Rs-5:537 G/T,Rs-6: 837 G/T,Rs-7: 936 A/G,Rs-8: 952A/C,Rs-9: 1047 T/G,Rs-10: 1062 C/T,Rs-11: 1287C/T,Rs-12: 1350A/C,Rs-13: 1362 C/T,Rs-14: 1371 C/T,Rs-15: 1503 T/C,Rs-16: 1536 T/C,Rs-17: 1737 T/C,Rs-18: 1788 C/T.The genotype and gene frequency of the selected line of S.constricta that were selected randomly were further assayed with the method of MassARRAY.Genetic structure was analyzed by Cervus 3.0software,the results showed that except the Rs-13 locus,the rest were in Hardy-Weinberg equilibrium.The average of Hardy-Weinberg value was0.581.The average PIC was 0.237,belonged to low state.Association analysis indicated that individuals with different genotypes of locus Rs-5:537 G/T,Rs-10: 1062 C/T showed significant difference(P<0.05)at shell length,shell width or shell height.The seven diplotypes consisted of the thirteen SNPs were different in the body weight and shell heigth.Diplotype S6 showed a significantly higher value of body weight compared with genotype S3,S6 and S7(P<0.05).Diplotype S6 showed significantly higher than shell height of S7(P<0.05).Meanwhile diplotype S6 is the biggest among all of seven diplotypes.The SNP markers founded in alpha amylase gene exon would be candidate genetic markers,retaining diplotype S6 and eliminating S7 could provide help to the molecular marker assisted breeding of S.constricta. |
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