Growth Rate and Growth Model of the F5 Selected Lines for Four Shell Colors of Pinctada Martensii （Dunker） Cultured in Deepwater Area of Beibu Bay in Zhanjiang and Their Genetic Diversity Analysis Using SSR Molecular Markers
|School||Guangdong Ocean University|
|Keywords||Pinctada martensii (Dunker) the F5 shell color selected lines growth model microsatellite DNA genetic diversity|
In this research, we selected four shell colors, such as black, white, red and yellow of Pinctada martensii as study objects, which were the fifth selected generation (F5) after color selection in deep waters of Beibu bay in Zhanjiang. Four groups of shell color line selected generation (F5) were compared with the common population on growth rate. The growth model of four shell color line was fitted. This researche also used microsatellite (SSR) markers to analyze genetic diversity and genetic differentiation of four shell color line. The results can provide a scientific basis on germplasm conservation and aquaculture production of P.martensii, and further genetic background information for the breeding of P.martensii as well. The main results are listed as follows:1. After one and a half year’s cultivation, we assessed growth rate of the fifth selected generation (F5) for four shell color lines and ordinary populations, and measured four morphological indicators of shell length (SL), shell width (SB), shell height (SH), stranded wire length (HL) and three weight indicators including body weight (TW), soft body weight (IW), shell weight (SW). The results showed that the livability of black, white, red, yellow shell color selected lines separately were 47.68%, 45.63%, 46.82%, 46.93%, 39.47%. The average livability of the selected lines had increased by 18.48% than the common population. There were significant differences of the growth rate no matter among the selected lines or between the selected lines and ordinary population. The growth rate of the four shell color lines was significantly higher than ordinary population. In the four shell color lines, the white shell color line grew fastest, second the red shell color line, third the black shell color line, last the yellow shell color line. The indicators of shell height, shell weight in the white shell color line, respectively, increased 15.79%, 47.55% than the ordinary population. The indicators of shell height, shell weight in the red shell color line, respectively, increased 12.29%, 37.97% than the ordinary population. The indicators of shell height, shell weight in the black shell color line, respectively, increased 7.47%, 31.18% than the ordinary population. The indicators of shell height, shell weight in the yellow shell color line, respectively, increased 8.55%, 23.75% than the ordinary population.Through the compared study of parameter of the economic traits between the F5 generation of shell color lines, we found out that the selected lines and ordinary population have no significant differences in shell length/shell height, shell width/ shell height, soft body weight/body weight, but significant differences in body weight/shell height and shell weight/shell height. The shell length/shell height parameters in order are white≥black≥common≥yellow≥red (P>0.05), the shell width/shell height parameters in order are black≥white≥red≥yellow≥common (P>0.05), the body weight/shell height parameters in order are white≥red≥black≥yellow > common (P<0.05), the shell weight/shell height parameters in order are white≥black≥red≥yellow > common (P<0.05), the soft body weight/body weight parameters in order are red≥black≥yellow≥white≥common (P>0.05).2. We used 4 non-linear growth models: von Bertalanffy, Gompertz, Logistic and Brody to fit the morphological traits of four shell color lines (such as: shell length, shell width and shell height), growth and development traits of weight respectively. According to Levenberg-Marquardt iteration method we got growth parameters of each model, and with the optimal value of each parameter we may get the best fitting growth model. The results showed that: in the first half growing year of the selected lines of four shell color lines for P.martensii Dunker, Brody model is the optimal growth model of the shell length (SL), shell width (SB), shell height (SH) and stranded wire length (HL) while von Bertalanffy model is the optimal growth model of body weight (TW). The comparison on growth curve and fitting curve showed that, in deepwater area of Beibu bay in Zhanjiang, P.martensii shell length (SL), shell width (SB), shell height (SH), stranded wire length (HL) grew fast in their early age but getting slow in their late age; however, body weight (TW) grew slow in their early age but getting fast in their late age.3. By using SSR markers, we used eight pairs of microsatellite primers to analyze their genetic diversity of black, white, red, yellow four shell color lines for P.martensii Dunker. The results showed that 42 alleles are detected among eight micro-satellite loci, each loci is 4-7 alleles, and the average is 5.25 locis; the average number of alleles in four selected lines are 4.7500, 4.8750, 4.6250, 4.5000; the average on expected heterozygosity are 0.6850, 0.6831, 0.6730, 0.6622; Shannon diversity index are 1.2750, 1.2743, 1.2565, 1.2338; the average on polymorphism information content PIC are 0.6190, 0.6182, 0.6230, 0.6025. These indicated that four selected lines have higher genetic diversity and great potential for genetic selection; Hardy-Weinberg equilibrium genetic deviation index D in four shell color lines is negative, which indicated that four selected populations have different level of the heterozygote deficiency; by using 8 micro-satellite loci, we had analyzed respectively F-statistic of the four shell color lines, the inbreeding coefficient Fis of four selected lines valued between 0.0701 and 0.7952, on an average with 0.4608, a total population base Guinea Fit inbreeding coefficient has the values between 0.0927 and 0.8023, on an average with 0.4848, coefficient of genetic differentiation Fst valued between 0.0236 and 0.1057, on an average of Fst was 0.0445, indicating that in populations with mild side degree of differentiation levels, the value of gene flow (Nm) among four populations was from 2.1142 to 10.3254, on an average with 5.3618; by using Popgene 32 we can calculate Nei’s standard genetic distance DS of the four selected populations, and then use the MEGA 4 to get cluster analysis of four selected lines. The results showed that Nei’s standard genetic distance in any two groups of the four shell color line is between 0.0629 and 0.1729. The genetic distance between the white shell color line and the red shell color line is the smallest (0.0629), the genetic distance between black shell color line and the white shell color line is the largest (0.1729). The cluster analysis showed that the black shell color line and yellow shell color line first get together as one, while the white shell color line and red shell color line get together as another.