| Pinctada fucata was selected for breeding in an unreasonable way lead toseriousinbreeding in commercialized producein the long-term time. With the addition of theeffect of inefficiency cultivation methods and environmental pollution in cultivation, thegrowth and themortality of P. fucata is decreasing and increasing, repectively, So that itis important to improve the growth and survival traits of P. fucata using method ofbreeding. Growth and survival traits were analyzed for selection in P. fucata familiesbreeding line in this study. Then heritabilities and genetic correlations, selectionreactions, realized heritabilities, genetic gains of four growth traits were analyzed.Results of analysis mentioned above are as following:1. Comparison of growth performances infamiliesofP. fucataTwenty five third generation families were constructed in2011for Pinctada fucata.All families were measured by shell length, shell height, shell width and body weightevery two months during4－month old to12－month old in P. fucata. Growth laws offour traits were analyzed and the grow performance were compared among families.The survival rates of twenty four families were record and compared with each other toidentified higher survival rate families. The result showed that shell traits grow faster instage of4~8month old than in8~12month old, body weight grow faster in stage of8~12month old than in4~8month old. Difference of growth low was found betweenfamilies in different initial mean of four traits, growth curves of shell traits and bodyweight of families those had bigger initial mean looked like parabola and linear,respectively. Growth curves of shell traits and body weight families those had smallerinitial mean looked like linear and index curve, respectively. The mean of four traits ofdifferent families was between36.92~51.53mm,36.92~50.56mm,13.91~20.19mmand8.99~24.72g, respectively. Total mean of four traits in all families was41.52mm、42.36mm、16.01mm and14.08g, respectively. Survival rate of different families and all families was between34%~73%and52%, respectively. Ten families of grow fastand twelve families of higher survival rate were selected, respectively. Consider of bothgrowth traits and survival rate, five families were selected for growth fast and highersurvival families. They were family no.5, no.23, no.26, no.27and no.29, respectively.2. Estimates of genetic parameters and breeding value for growth traits in juvenilepearl oyster P.fucataThe aim of this study is to estimate genetic parameters of growth straits in thejuvenile P. fucata. Thirty three full sib families were constructed by artificialfertilization. Fifty162day old individuals were randomly sampled from each family.Shell length(SL), shell height(SH), shell width (SW)and body weight(BW) weremeasured, and were used for genetic analysis using maximum likelihood algorithmbased on animal model. The results showed that the total phenotypic means of fourgrowth traitswere16.28±4.46mm,14.85±4.39mm,4.58±1.52mm,0.66±0.67g,respectively. The significant differences were found between different traits in differentfamilies, indicating that family factors have significant influences on growth traits in thejuvenile P. fucata (P<0.01). The heritability of these four traits were0.202±0.020,0.203±0.020,0.200±0.021and0.204±0.020, respectively, indicating that there wasstill to some extent selective potential with family selection. The pair wise phenotypicand genetic correlations between growth traits were0.667～0.698and0.685～0.959,respectively. It is predictable that when one trait is genetically improved, the others canbe improved as well since the phenotypic and genetic correlations between four traitsare positively high. The genetic correlation between shell width and body weight wasthe highest (0.959), so it is best to improve body weight through shell width.3. Estimation of selection response and genetic gain in three generations of P.fucatabreeding lineThe shell length, shell height, shell width and body weight of three generations of P.fucata breeding line were compared at7month old. Each latter generation grow fastsignificantly than the former generation (P<0.05). Response to the first (F1'F2) andsecond (F2'F3) selections of the four growth traits in P. fucata breeding line was0.34~0.76and0.22~0.38, respectively. Realized heritabilities of the first and secondselections for four growth traits was0.31~0.39and0.30~0.33, respectively. All realized heritabilities were high when ranked, indicating there was enough additivegenetic effect in four growth traits to be selected. Genetic gains of the four growth traitsof F3generation were lower than that of F2generation, being8.22%~12.99%and3.68%~7.18%, respectively. Cumulative genetic gains of the four growth traits were12.19%，13.42%，18.57%and21.11%, respectively. All results indicated there was high geneticselective efficiency in P. fucata breeding line. Results were different to select familiesaccording to breeding value and phenotypic value, respectively. Average breeding valueof first fifteen families of former method is4.36~6.54times than latter method,indicating that selection efficiency according to breeding value was higher than ofphenotypic value. |
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