| In order to find out the main growth traits of portunus trituberculatus which have influence on body weight, and define degree of correlation among characters. Thirty eight full-sib groups and fifteen half-sib groups of portunus trituberculatus were obtained by directional mating techniques. Full carapace width(X1),carapace width(X2),carapace length(X3),body height(X4),and body weight(Y)of each family on 80d,100d and 120d were measured. The phenotype correlation coefficients and the genetic correlation coefficients were calculated by correlation analysis at the different ages. The first 4 morphometric attributes(X1-X4) were used as independent variables, and body weight(Y) was used as a dependent variable for path analysis. Path coefficients, determination coefficients were calculated in path analysis. The results showed that the phenotypic correlation of the five traits was between 0.759 and 0.972,and the genetic correlation was between 0.170 and 0.975. All five correlation coefficients achieved very significant difference (P<0.01) levels. The direct effects by the characters have an order at the three stages,80d:X1>X2>X3>X4,100d:X1> X3> X2> X4,120d:X3> X2> X1> X4, among them X1 weighted the most to the body weight on 80d and 100d, X1 and X3 weighted the most to the body weight on 120d. Full carapace width which have the largest direct impact on body weight (0.4719)is the most important indicators for indirect selection of body weight. Multiple regression equation of (X1,X2,X3,X4) to body weight at different developmental stages was obtained as:80d Y=-54.113+0.491X1+0.632X2+0.325X3+0.451X4; 100d Y=-123.484+0.627X1+0.928X2+1.433X3+0.152X4; 120d Y=-158.239+0.137X1+1.410X2+2.370 X3+0.800 X4.The high compound correlation index(R2=0.960,0.971,0.892) indicated that these growth traits had direct influence on body weight. Efficient scheme of multiple trait selection will be made if we obtain definite quantitative relationship between each two characters. This study provides theoretical evidence and perfect measure target for breeding of portunus trituberculatus.Six microsatellite markers were used to estimate the kinship and examine the genetic diversity of six Portunus trituberculatus families. All the microsatellite loci displayed high genetic difference among the six families. The polymorphic information content (PTC) of the six loci was 0.6045 at loci Pot09,0.6072 at loci Pot14,0.8130 at loci Pot17,0.6870 at loci Potl8,0.7839 at loci Pot25,0.6330 at loci Pot42. Thirty two alleles were detected in six families tested at six microsatellite loci. The number of the alleles at each locus was between four and eight. Seven family unique alleles were found out:two in 2# family, two in 3# family, one in 1#family, one in 5# family, one in 6# family. Family unique allele was not found in family 4#. Based on the unique alleles among the families, each family could be distinguished from the others.1# and 6#family were identified from the other families at locus Pot18.3#was identified from the other families at locus Pot14 and Potl7.5#family was identified from the other families at locus Pot42, and 2#family was identified from the other families. It was consider that unique alleles at loci Pot18, loci Pot114 and loci Pot17, loci Pot42, loci Pot17 and loci Pot25 could be used as family markers of 1# and 6# family,3# family,5# family,2#family, and they could be used to identify these families. Our results suggest that the six families could be distinguished by these six microsatellite markers, and the six families could be identified using at least two microsatellite markers:Pot17 and Pot18. Based on these results, it was concluded that that the use of a number of microsatellite markers represented a realistic and effective way in the selection program of Portunus trituberculatus.We detected the application of two pairs of microsatellite markers, Pot17 and Pot42, to Portunus trituberculatus parentage determination on the basis of four families obtained by directional mating techniques. Eleven alleles were acquired at two microsatellite DNA loci (six at locus Pot 17 and five at locus Pot42) by investigating 5 parents and 98 offsprings in the four families. As analyzed, the gene frequencies detected by locus Pot17 and Pot42 were between 0.0291 and 0.3592, expected heterozygosity was 0.7740 at locus Pot17 and 0.7577 at locus Pot42, observed heterozygosity was 0.6214 at locus Pot17 and 0.6796 at locus Pot42, and the polymorphism information content (PIC) was 0.7373 at locus Pot17 and 0.7129 at locus Pot42. The results showed that the cumulate power of discrimination(CDp) of Pot17 and Pot42 amounted to0.995, Pot17 and Pot42 had high discriminating and can be used to the Portunus trituberculatus parentage determination.
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