| The pearl cultivated by Hyriopsis cumingii is colorful and bright luster,which is the primary breeding strain for freshwater pearl production in China..In recent years,our laboratory has carried out a lot of research on the selective breeding of different strains of H.cumingii,especially the evaluation of genetic parameters for the growth traits and inner shell color,which has laid the foundation for the selective breeding of H.cumingii.Due to the long culture time for pearl production,very little is known about the genetic parameters of commercially important pearl traits.This experiment was based on previous studies in our lab to analyze the pearl traits,which produced by the golden strains of H.cumingii,including the correlation between pearl traits with donor mussels and host mussels,and the genetic parameters of donor-derived and host-derived pearl quality traits.This experiment also evaluated the effectiveness of selective breeding in the second generation of golden strain H.cumingii,and calculated the genetic parameters for early and late traits of growth traits and inner shell color traits at different monthly ages to provide a reference and basis for the effectiveness of early selection.It mainly includes the following contents:1.Correlation analysis between the traits of donor and host mussels and the nonnucleated pearl quality traits in the golden strain of Hyriopsis cumingii1026 and 342 from the first generation of golden strain H.cumingii were randomly selected as host and donor mussels,and the saibo of mantle tissue from 342 donor mussels were implanted into 1026 host mussels.The mantle tissue from each donor mussel could be implanted into three host mussels,each one is implanted with20 pieces of mantle.After two years of culture,380 host mussels were randomly selected and a total of 7587 pearls were obtained.The results showed that the variation coefficient of color parameters L* and d E* was small,but a* and b* had a large variation coefficient.The larger the b* value,the deeper the golden color.There was no significant correlation between a(9)and b(9),that is,a(9)had no significant effect on b(9),suggesting that the b(9)value may be the main parameter used to directly evaluate pearl color in the golden strain of H.cumingii.The results also showed that pearl weight had significant correlation with shell width and body weight,pearl size had significant correlation with all four growth traits,and pearl roundness had significant positive correlation with color parameter d E(9).The pearl color parameter b(9)was significantly correlated with the inner shell color a(9),b(9),d E(9)and the inner shell luster.The correlation between pearl color b(9)and inner shell color b(9)was strongest among them.There were significant correlations between pearl luster with inner shell color and inner shell luster,and the correlation between pearl luster and inner shell luster was the strongest.Therefore,different selective breeding plans can be made for host mussels and donor mussels according to the desired pearl quality traits.2.Estimation of non-nucleated pearl quality traits from donor and host musselderived genetic parameters in the golden strain of Hyriopsis cumingiiMicrosatellite markers were used to identify the parentage of donor and host mussels.The results showed that 298 donor mussels constituted 21 full-sib families,and 355 host mussels constituted 25 full-sib families,among which 7 full-sib families of donor and host mussels belonged to the same full-sib family.Host-derived heritability estimates for pearl luster and color were low to moderate,while heritability estimates for pearl size,weight and roundness were moderate(0.24,0.28 and 0.16 respectively).Donor-derived heritability estimates for pearl luster and color parameters L(9),a(9),b(9),d E(9)were moderate to high(0.37,0.24,0.22,0.47,and 0.27respectively),while heritability estimates for pearl weight,size and roundness were low to moderate.The genetic contribution of the donor and host(D×H)interaction on pearl color and pearl luster were low,while the genetic contribution of the D×H interaction on pearl size,weight and roundness were moderate to high.Therefore,in the future pearl culture project,it is necessary to explore the best combination of donor and host mussel with different growth traits to improve the pearl size,weight and roundness.while programs to improve the pearl color and luster traits should be achievable through target donor mussels with superior color and luster.3.Estimation on the breeding effect and value in the second generation of golden strain Hyriopsis cumingiiA total of 100 well-developed H.cumingii were selected in a 3:2 ratio of females to males.22 maternal half-sib families of H.cumingii were bred at the same time and the breeding values of the 22 half-sib families were evaluated for growth traits and inner shell color.The results showed that the breeding values and phenotypic values of shell length in no.18 family were all high at 5,12 and 17 months old,while the breeding values and phenotypic values of shell length in no.4 and 20 family were both high at 17 months old.The breeding values of shell height were both high at different months old in no.2 and no.18 families,but phenotypic values of shell height were both high at different months old in no.19 families,and high breeding values and phenotypic values in no.4,14 and 20 families at 17 months old.The breeding values of shell width were both high at different months old in no.2 family,and the breeding values and phenotypic values were both high in no.4 family at 17 months old.The breeding values of body weight were both high at different months old in no.16 family,while the breeding values and phenotypic values of no.4,20 and 22 were both high at 17 months old.Therefore,no.2,4,14,16,18,20,22 families can be extended in Wuyi.The average value of color parameter b(9)was 6.02,8.36 and 10.86 at 5,12 and 17 months old,respectively,indicating that the value of b(9)accumulated with the increase of month age.The families with high b(9)values at different ages were No.2,9 and 18,and No.6,9 and 18 had high breeding values with b(9).Therefore,No.2,6,9 and 18 could be promoted as parents to breed offspring to improve the inner shell color of the strains.4.Evaluation of early breeding effects of growth traits and inner shell color parameters of Hyriopsis cumingiiWhen the second generation of H.cumingii reached 5 months old,50% selection rate was selected based on shell length as the target trait and 50% selection rate was selected based on shell color(golden color),and divided into selective breeding group and control group.In this study,the mean values of growth traits and inner shell color parameters of H.cumingii at different months old were calculated,and the differences of phenotypic traits between the breeding group and the control group were compared,as well as the genetic parameters were estimation of early and late traits in growth traits and inner shell color parameters.The results showed that the average growth traits increased with the increase of month age,but the average inner shell color did not change much with the increase of month age.As well as the breeding group and control group of shell length,shell height,shell width traits were no significant differences at 5 months old(P(29)0.05),but there were significant differences in four growth traits between the breeding group and the control group at 12 and 17 months old.The color parameters b(9)of the breeding group were much higher than that of the control group at different months old,and the color parameters b(9)of the breeding group increased with the increase of months old.The d E(9)showed significant difference between the two groups at 12 months and 17 months old.The results of genetic parameter analysis showed that the heritability of growth traits and inner shell color was medium to high in different months old,indicating that the growth traits and inner shell color of H.cumingii could be improved by selective breeding.The genetic correlations for the shell height were extremely high between different monthly ages,indicating that the selection of shell height traits at 5 months old had an effect on the height traits at 12 and 17 months old,while the selection of shell length,shell width and body weight at 12 months had a great effect on the shell length,shell width and body weight traits at 17 months,suggesting that enough individuals should be retained for early selection for H.cumingii at the age of 5 months old,and the second selection should be made at the age of 12 months old.The genetic correlation in b(9)value were all highly significant within the breeding group,suggesting that the inner shell color of early selection was effective for golden strain of H.cumingii. |
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