Quantity Genetic Analysis Of Paralichthys Olivaceus Families And QTL Mapping For Metamorphosis Direction

Paralichthys olivaceus is one of the most important aquaculture species in China, However, the intensive breeding and many generations of inbreeding in recent years result in poor disease resistance and slow growth during culturing. Therefore, it is necessary to improve the quality and productivity of P. olivaceus through selective breeding. This study includes the following three portions:To study the relationship between morphometric traits and body weight of P. olivaceus at different growth stages, Measure 22 morphometric traits and body weight of P. olivaceus at 8 and 14 month. The data were statistically processed by correlation analysis, path analysis, and stepwise regression analysis, then established the multivariate regression equation. Determined the traits included in equation as independent variables and determined body weight as dependent variable for six kinds of curve models fitting, to select the optimal fitting model. The results showed that: The multivariate regression equation was Y =-119.541 + 7.191 X18 + 10.135 X4 + 7.197 X11 for 8 month, and Y=-484.931 + 31.959 X18 + 81.928 X14- 17.889 X9 for 14 month. It suggested that the vital morphometric traits which affected body weight at two growth stages were different. At 8 month, all the three optimal fitting models were linear model, which were Y=-117.866 + 15.724 X18, Y=-94.579 + 24.763 X4, Y=-100.602 + 33.184 X11, respectively. At 14 month, however, all the three optimal fitting models were power model, which were Y=0.036 X183.063, Y=0.095 X142.587, Y=62.249 X91.584, respectively. R2 for the multivariate regression equation at 8 month and 14 month was 0.965 and 0.984, respectively, which indicated the equations can be very well used to predict the body weight of P. olivaceus. R2 for the linear model of X11 at 8 month and the power models of X9 and X14 at 14 month were all lower than 0.85, indicated X11, X9 and X14 cannot explain the body weight of P. olivaceus fittingly as a single independent variable. X18 appeared in multivariate regression equations at two growth stages, indicated X18 was a very important morphometric trait which affected the body weight, so X18 can be regarded as an assisted selection trait of body weight. All the results provide the theory basis for selective breeding at different developments.To determine the conditional and unconditional variance components and estimate the heritability, data for total length, body width, and body weight were collected from 38 families of P. olivaceus at 93, 141, and 203 day after hatching. A genetic model includes additive effect, dominant effect and environment interaction effect(ADE model) was used to analyze data. The environment effects to three traits were significant at early development and late development. The distributions of unconditional variance components for three traits were roughly the same except total length after 141 day after hatching, indicated that from this time, the body weight increasing was mainly rely on the body width increasing. The dominant variance components through three stages were detected at a low level, which indicated all three stages showed non-significant potential of heterosis. The narrow and broad sense heritability of three traits reached the highest at 141 day after hatching(0.386 and 0.400 on averages). The three detective intervals were too long to determine the activity of genes, it should be shorten in further study. All those results provided practical information and suggestions to determine the optimum periods at which to carry out genetic improvement.To study principle of the eye move during P. olivaceus development, the QTL analyze was carried out. 24 linkages were established and the marker coverage reached 64%. After the primary QTL analyze, only one QTL was found on linkage no.1, the length of the QTL was 22 c M. Then increased the maker density on linkage no.1, established three kinds of maps included integration map, female map and male map. The lengths of three maps were 55.3c M, 59.2c M and 59.2c M. The marker coverages were 95.4%, 94.7% and 93.1%, respectively. Acquire four QTL by using integration map, the length were 0.9c M, 2.6c M, 0.2c M and 0.3c M respectively, acquire two QTL by using female map, both 1.8c M long, acquire two QTL by using male map, respectively were 0.2c M and 2.7c M. All these results provide the reference for further study.