| The Oujiang color common carp (Cyprinus carpio var. color) is a widespread variant of common carp found in the Oujiang River basin of Zhejiang Province,and it has been locally cultured in rice paddies and yards for more than 1200 years. In 2001, five hatchery strains were established according to body color patterns and growth rate, and the fifth generation of hatchery strains was reached in 2009. In these studies, genetic effects and combination abilities of growth traits were studied for the five complete set lines of Oujiang color common carp using quantitative genetics methods and diallel cross design. Furthermore, based on microsatellite loci, genetic differentiation between the complete set lines and wild populations were detected to identify the hatchery escapees of Oujiang color common carp in the wild pool.1. Study on genetic variance and combining ability for the complete set lines of Oujiang color common carpThe additive×dominance mixed genetic model was used to analyze the combining abilities of the five growth traits (body weight, total length, standard length, pre-dorsal height and pre-dorsal width). The results indicated that all five growth traits displayed the high level of specific combining ability(SCA)which accounted for over 72℅ of total phenotypic variance, and SCA were significant for the body-weight,total length and standard length (P<0.05). Moreover, the narrow-sense heritabilities were not detected for all five traits, but the broad-sense heritabilities were found very high, which showed that the heterosis would be easily obtained by means of cross among the complete set lines. The predicted dominance effect of parents domenstrated that the significant heterosis existed in the combinations of"whole red"(S1)×"whole red with big black patch"(S2) ,"whole red with big black patch"(S2)×"whole while"(S4),"whole red with big black patch"(S2)×"whole while with big black patch"(S5) and"whole while"(S4)×"whole while with big black patch"(S5).2. Analysis of heterosis and genetic correlation for the complete set lines of Oujiang color common carpThe additive×dominance mixed genetic model was also used to analyze heterosis and genetic correlations for five growth traits from the five complete set lines of Oujiang color common carp. The results indicated that significant heterosis was observed in the combinations of S1×S2,S2×S5,S2×S4 and S4×S5,whereas the negative heterosis were observed in the combinations of S2×S3 and S3×S4. Significant dominance correlations were found between body weight, total length and standard lenght(rD>0.985), however no additive correlations were found for all five growth traits.3. Genetic analysis of maternal, paternal effects and study on the best combination of complete set lines in Oujiang color common carpReciprocal differences have always been observed for the given traits in fish breeding programs, but maternal and paternal genetic effects have often been omitted in the evaluation of genetic variance. In this study, a mixed genetic model was used to conduct maternal and paternal genetic effects analysis of five complete set lines in Oujiang color common carp. The results indicated there were not significant maternal and paternal genetic effects in all the five growth traits, only weakly parental genetic effect in standard lenght and pro-dorsal width. Significant dominance effect were observed in all the five growth traits (accounting for over 72℅ of total phenotypic variance), which illustrated that obvious heterosis can be obtained among the complete set lines in this species. Genetic effects of dominance (D) for growth traits indicate that S2 would be the best maternal materials in cross combinations. The best combination was cross of S4♀×S5♂, then followed by the crosses of S2♀×S4♂and S2♀×S5♂.4. Genetic identifying the escapees from the selective strains of Oujiang color common carp in the wild populationsThe escape or release of cultured and domesticated organisms into the wild poses a threat to the genetic integrity of natural populations. Based on data from 17 microsatellite loci, genetic differentiation between wild and hatchery Oujiang color common carp Cyprinus carpio var. color was investigated, and the potential application in identifying the escapees of hatchery strains was assessed by using Bayesian genetic assignment. No significant differences were observed between pooled hatchery and pooled wild populations in terms of allelic richness (AR), observed heterozygosity (HO), and inbreeding coefficient (FIS). Analysis of molecular variance (AMOVA) and pairwise FST comparisons suggested significant genetic differentiation between hatchery strains, and between hatchery and wild populations, which was further confirmed by the principal components analysis and the Bayesian clustering analysis. Bayesian genetic alignment showed high accuracy of self-assignment (ranging from 86.0 to 96.0%) in the original populations, demonstrating the ability to identify escapees of hatchery Oujiang color common carp in the wild population. |
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