Genetic Evaluation On The Mass-selected Lines Of The Pearl Oyser Pinctada Fucata

The pearl oyster Pinctada fucata is one of shellfish for China’sproduction of seawater pearl. In recent years, great mortalities occurredfrequently, the individual miniaturized also appeared (e.g. Yan et al.2001).Therefore, a selective breeding program has been initiated for geneticimprovement of P. fucata. In order to ensure the sustainability of geneticimprovement, a better understanding of the genetic structure of itspopulations or pedigrees is required. Microsatellite markers is an importantmeans of genetic analysis. To this end, this paper carried out microsatellitemarkers screening and the genetic analysis in breeding populations P.fucata,with a view to provide theoretical guidance for breeding in P.fucata. Themain results are as follows:1. Microsatellite markers screening in Pinctada fucata. In this study,we developed a new set of20microsatellite DNA markers for P. fucata byusing next generation sequencing. Polymorphism of these loci wasevaluated with a wild population of P. fucata. The number of alleles perlocus ranged from2to6. The observed and expect heterozygosities rangedfrom0.0263to1.0000and0.0506to0.7424, respectively. After Bonferronicorrection, ten loci deviated from Hardy-Weinberg equilibrium possibly due to homozygote excess. In this study, we developed a new set of15microsatellite DNA markers for P. fucata by using genome sequencingresults. Polymorphism of these loci was evaluated with a wild populationof P. fucata. The number of alleles per locus ranged from3to8. Theobserved and expect heterozygosities ranged from0.1154to0.6216and0.4950to0.8491, respectively. Fourteen loci deviated fromHardy-Weinberg equilibrium possibly due to homozygote excess. Themarkers isolated in this study can be used to analyze genetic diversity andmolecular marker-assisted selection in pearl oysters and so on.2. Correlation analysis of genetic diversity with its growth traits of thepopulation. Using35microsatellite markers, we analyzed12populations(Constructed in March,2012). The results showed a significant correlationbetween five microsatellite markers and its growth traits.3loci containingsix kinds of genotypes had significant on body weight,5loci containingeight kinds of genotypes had significant on shell length,3loci containingeight kinds of genotypes had significant on shell height, and4locicontaining seven kinds of genotypes had significant on shell width.3. Genetic diversity of mass-selected populations. Using6microsatellite markers, we analyzed17populations (Respectivelyconstructed in March,2012and June,2012). A total of29alleles weredetected from680individuals. The observed allele number was2-7, average effective allele number was2.06-3.07, average observedheterozygosity was0.31-0.58, and average expected heterozygosity was0.46-0.65. The polymorphic information content (PIC) for the17populations were0.39-0.58,11populations are highly polymorphism(PIC≥0.5); There are different degrees loss of heterozygosity of17groupsin different microsatellite loci. The results above provide usefulinformation for the selective breeding and germplast conservation of P.fucata.4. Correlation between the genetic makeup and growth performancesof selected populations. Using six pair microsatellite primers analyzedgenetic diversity of12breeding populations of P.fucata, explored thecorrelation between each group of traits and genetic diversity from theperspective of the individual and population genetic structure. The resultsshowed that a positive correlation between groups’ heterozygosity and theweight, shell length, shell height, shell width, respectively. R2respectivelyare0.2779、0.0721、0.0344、0.3071. Three selected populations (DS22、DY27、 SY29) showed a negative correlation between individualheterozygosity and weight, linear regression equation: y=-0.9599x+38.018, y=-1.0171x+31.996, y=-7.6659x+30.527, the others nightselected populations (SS21、SD23、BS24、YS28、YB210、SB213、BD212、BY214、 YD215) showed a positive correlation between individual heterozygosity and weight. These results indicated that the greater theindividual’s heterozygosity, the better performance for traits. Thus, in thegenetic improvement of breeding, increasing P.fucata heterozygosity isnecessary.