Genetic Analysis On Economic Traits Of The Pearl Oyster Pinctada Fucata

The pearl oyster Pinctada fucata is is the main pearl oyster to produce the pearl inChina. Marine pearl culture industry suffered a great loss because of environmentalfactors and inbreeding in recent years. So it is necessary to conduct the study on theGenetic Analysis of the cultured population.Main economic traits of Pinctada fucatawere analyzed in this study, using methods such as multivariate statistical analysis, pathanalysis and linear model and so on. The results are as following:1.Morphological variations and discriminant analysis of four populations ofPinctadafucataBased on9morphological characters,morphological variations of four populations（Guangxi, GX; Leizhou, LZ; Vietnam, YN; Sanya, SY）of pearl oystersPinctadafucatawere investigatedusing multivariate morphometrics. As the result ofprincipal component analysis （PCA）, three principal components were constructed byfactor loadings, in which the first principal component （PC） was affected by sevencharacters, PC2and PC3each by1character.The contribution ratios of three PCs were55.577%,14.475%and10.545%, respectively. The results of PCA and cluster analysisrevealed that the morphological characters of Shenzhen and Yuenan populations weresimilar and much more different from Sanya population. The discriminant functions offour P.fucata populations were established, and the discriminant accuracy was50%,58%,60%,60%for GX, LZ, YN and SY, respectively, with the average discriminantaccuracy being57%.The morphological variation of P.fucata was aresult of the jointeffect of genetic components and environment, so it can be a reference for broodstockselection in genetic improvement.2. Correlation and Path Analysis to Quantitative Traits of Pinctada fucata in DifferentGenderPinctada fucata was one of most important oyster species those cultured marine pearls, and it was valuable to detect the influence of different genders on correlation andpath analysis among growth traits in P. fucata. Four hundred sixteen individuals weresampled randomly from third generation selective line in one-year old P. fucata, weremeasured by shell length, shell height, shell width and body-tissue weight, then weredistinguished by gender. The correlation between quantitative traits in different genderswas analyzed, then path coefficient and multiple regression between phenotypic traitsand body-tissue weight was analyzed in different genders, respectively. The resultshowed that growth traits of males were highly significant bigger than of females （P<0.01）. Correlation coefficients between different growth traits were highly significantboth in males and females （P <0.01）. The phenotypic trait that has largest influence onbody-tissue weight was shell width both in males and female. In decision coefficient onbody-tissue weight, the joint decision coefficient between shell height and shell widthrank firstly both in males and females, but the joint decision coefficient between shelllength and shell height rank secondly in female, and immediate decision coefficient ofshell width rank secondly in males. Shell length was omitted in multiple regressionanalysis, because of its path coefficient is insignificant. Then regression equation ofbody-tissue weight in females and females was Yfemale=-8.0139+0.0828X₁+0.1139X₂+0.2554X₃and Ymale=-6.6635+0.1201X₂+0.2810X₃, respectively. Allregression coefficients of two equations were significant when tested. All resultsindicated that the best effect of indirect selection would be obtained when improve body–tissue weight via shell width. This study provided a theoretical basis and measureindicatrix for the breeding of P fucuta.3. Estimates of strain additive and non-additive genetic effects for growth traits in adiallel cross of three strains of pearl oyster （Pinctada fucata）Strain’s additive genetic effects, heterosis and reciprocal cross effects wereestimated upon complete diallel crosses from three base populations （Beihai, BH,Xuwen, XW and Sanya, SY） of pearl oysters Pinctada fucata. Nine populations of thefirst generation were obtained.. The results show that the highest strain’s additivegenetic effect was for the Beihai strain （+5.7%） and the lowest for the Sanya strain（4.3%） for body weight. Similar patterns of strain’s additive genetic effects wereobserved for shell length, shell height and shell width. Average heterotic outcomes forall growth traits were significant （P<0.01）, and ranged from+6.1%for shell length to +19.1%for body weight. The order of strain’s reciprocal cross effects among the fourgrowth traits was BH> XW> SY.4. growth traits comparison of complete diallel cross of three populations of pearl oyster（Pinctada fucata）Complete diallel crosses within and among geographically different populations,Sanya（SY） Shenzhen（SZ） and Vietnam （YN） of P. fucata were made in order to breednew strains for genetic improvement. Nine F1populations have been obtained, includingthree purebreds and six crossbreds. Subsequently, their growth performances at differentdays were studied. The results show that in the growth performances were highest forthe SZSY population, followed by YNSY and then SZYN. At the same days thevariation of shell width was not significant. With the growth of P. fucata, shell length,shell height and shell width for each population will gradually slow. The meanperformance of the crossbreds generally higher than that of purebreds. In the differentstages, the heterosis is different of crossbreds,-68.66%～23.98%,-27.69%～82.11%and2.80%～49.12%, respectively. Heteroses were different for different combinationsand different traits. Heterosis for shell length, shell height, shell width and body weightwere hightest for Sanya population were26.71%,22.87%,18.5.6%and49.12%respectively, followed by SZYN and then YNSY. Yet the shell height of the hybridsSY♀×SZ♂showed the lowest heterosis rate （6.60%）; The shell width and body weightof the hybrids YN♀×SZ♂showed the lowest heterosis rate （3.32%） and （2.80%）; Theshell length of the hybrids SY♀×YN♂showed the lowest heterosis rate （6.17%）.