The Application Of Molecular Markers In Genetic Breeding Of Hybrid Scallop And Sea-cucumber

In order to solve some problems involving in genetic breeding of hybrid scallop and sea-cucumber, the molecular markers are applied to provide explains and methods for them from molecular genetic levels. This research includes two parts: One is using biostatistical method such as relative analysis, regression, ANOVA et al to detect the relationship between QTLs and QTLs, or QTLs and markers in hybrid scallop; the other part is using ISSR markers to detect the genetic variations between and among to different populations of sea-cucumber. The main results are as follows:1. Data for the study were collected from 52 hybrid Chinese scallop between Chlamys farreri and Chlamys nobilis at one year old in Rongcheng breeding field. The shell length (X₁), the shell thickness (X₂), the shell height (X₃), the body weight (Y) and the total weight (Z) were measured. The correlation coefficients matrix was calculated. The preceding three shell characters were used as independent variables, and the body weight was used as a dependent variable for path analysis, path coefficients (P_i), determination coefficients (d_i) and correlation index (R₂) were calculated. The result showed that three correlation coefficients between each shell character and the body weight were all in very significant difference (P<0.01). Shell height (X₃) gave predominant direct effect (P₃=0.6749) and determinacy on the body weight; it is the key effective factor. Shell length (X₁) gave slightly direct effect (P₁=0.2120) and significant indirect effect (0.5661) through shell height on the body weight. Shell thickness (X₂) gave slightly direct effect and indirect effect on the body weight. It was clear from the result of high correlation index (R₂=0.8219) that the path coefficient analysis could reveal the exact relationship between the independent variables and the depend variables. The multiple regression equation obtained to estimate body weight as Y=-38.7074+2.1427X₁ +2.1517 X₂ +7.2214X₃.The results provide theoretical evidence and perfect measure target for breeding of scallops.2. The objective of the study is to investigate QTLs associations with the threequantitative traits (body weight, height and length) within forty hybrid Chinese scallop between Chlamys farreri and Chlamys nobilis by using AFLP marker. Single factor analysis of variance was used to determine the significance of difference among genotype classes. Thirty-seven, thirty-six and thirty-five markers were respectively found to be associated with the body weight, height and length closure. The contribution rates were calculated separately. The mean of the two groups was significantly different by the t-test. Compared with the coherence of quantitative trait loci, the similarity between the body weight and the height of the shell is higher than the length of the shell. And most loci affected the same trait together. 3. In order to assess the utility of ISSR (Inter-Simple Sequence Repeat) markers for detecting the changes of genetic variation between and within two populations of sea-cucumber (Apostichopus japonicus) and for estimating their relationship, A total of 64 bands ranging in size from 300 to 1500 bp, corresponding to an average of 6.4 bands per primer, were generated using the 10 selected primers. Of these bands, 59 were polymorphic among 57 individuals, i.e. the percentage of polymorphic bands (PPB) for this species was 92.2%. The percentage of polymorphic bands (PPB) was 85.2% and 86.9 % for PL population and QD population, respectively. The observed number of alleles (Ao) was 1.8125 for PL population and 1.8281 for QD population; the effective number of alleles (Ae) was 1.6672 for PL population and 1.6026 for QD population; the gene diversity (He) was 0.3605 for PL population and 0.3428 for QD population; the Shannon's Information index (I) was 0.5150 for PL population and 0.4990 for QD population; the coefficient of overall genetic differentiation between populations (Gst) was 0.073 as estimated by partitioning of the total gene diversity. The gene diversity (He) was 0.3789 and the Shannon's diversity index was 0.5504 of the total variation between populations. Genetic distances (D) between populations are 0.0796.. A dendrogram of this genetic distance within population was constructed using Unweighted Pair-Group Method (UPGMA) with PHYLIP software...