| Double haploids have a very high genetic homozygosity, which are ideal parent materials of crossbreedings, produced by mitosis gynogenesis for Japanese flounder(Paralichthys olivaceus). However, for the high purity of double haploids individuals, their viability and fecundity are often too low to meet the needs of crossbreeding design that need sufficient number of distinctive breeding material and not directly as a parent for the species. Many studies have shown that, the viability of individuals is closely associated with segregation genes. Currently, sex determination of Japanese flounder is still a complex and unresolved issue. It’s generally considered that sex determination is relative to the genes on the chromosome and changing temperatures. As for gender-related genes and gene×environment interactions exist or not, it is worthy to study further.In this study, we used mitotic gynogenesis technology for double haploid eggs and hatched them. After 40 days, dividing them into three groups, breed them respectively at 20 ℃, 24 ℃, 28 ℃ until 150 days. Eventually, we obtained 212 double haploids. Based this group, we shtudied on interactions between genes and environment(temperature) on sex phenotype. Summarized as follows:1. Using 272 effective polymorphic SSR markers to correct a segregation distortion genetic linkage map based on Mapdisto and Distorted Map, while to construct an un-corrected segregation distortion map based on Joinmap 4, and compare the two maps: the observed genome length were 1961.02 c M and 945.31 c M, average distances were 9.61 c M and 4.22 c M, coverage ratios are 80.80% and 80.46%. The relative positions and distances of genetic markers were really changed.2. Based corrected and un-corrected segregation distortion maps, with corrected or uncorrected conditional probability of segregation distortion markers, using Bayesian model to dissect the genetic architectures of sex phenotype in different temperatures(20℃, 24℃, 28℃), including mapping main effect QTL and analysis of gene × environment interaction and analysis of epistasis QTL. The results showed that 1) different methods had different results of additive QTLs and epistatic QTLs of sex phenotype; 2) heritabilities(0.1%~4.95%) and additive effect values of sex phenotype were very low; 3) epistatic QTLs of sex phenotype had main contributions to phenotypic variation, which could account for 9.69%~19.05%, 3.20%~22.07%, 5.88%~18.08% and 8.66%~16.62%, respectively. In the corrected genetic linkage map, we detected three main effect QTLs located at 5[48.51]、12[14.30] and 20[0.00]. Of which, a negative additive effect one located at 5[48.51] could account for 3.97% of the phenotypic variation and gene × environment interaction effect value was 0.148; a positive additive effect one located at 12[14.30] could account for 3.36% of the phenotypic variation and gene×environment interaction effect value was 0.014; a negative additive effect one located at 20[0.00] QTL can could account for 3.23% of the phenotypic variation gene×environment interaction effect value was 0.061. And, the number of additive × additive interaction epistatic QTLs was 26, mainly distributed in No.1, No.2, No.4, No.5, No.8, No.10, No.11, No.19, No.20 and No.23 linkage groups, that could account for 9.69%~19.05% of phenotypic variation. Of which, the biggest heritability of epistatic QTLs was located at 19[176.47]×23[23.95].4. Based corrected and un-corrected segregation distortion maps, using segregation distortion loci to dissect the genetic structure of viability with threshold model, and compare the effects of corrected and un-corrected conditional probability of segregation distortion markers for test results. It was found that 1) the conditional probability corrected or not, test results were the same; 2) results of SDL mapping were different in corrected map and uncorrected map; 3)heritabilities of main effect SDLs was very low. In the corrected map, we detected to a lethal gene located at 12[11.38] that could account for 0.41% of variation of viability.The research results could provide ideas for QTL mapping of important economic traits, and a reference for MAS breeding and strain improvement in Japanese flounder(Paralichthys olivaceus). |
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