Genetic Analysis On Selected Populations Of Shrimp Fenneropenaeus Chinensis Named "Huanghai No.1"

The paper presented the effects of morphometric on body weight and genetic diversity of selected populations of Fenneropenaeus chinensis. The results would provide theoretic basis for artificial selection, varieties resource conservation and genetic improvement for F. chinensis. The main results were shown as follows:1. 100 five-month-old F. chinensis and 50 six-month-old F. chinensis were random-sampled for measuring the morphometric attributes. 15 morphometric attributes included the body weight, total length, body length, carapace length, first-sixth abdominal segment length, tail length, carapace width, carapace height, first abdominal segment width and first abdominal segment height. By correlation and path analysis, the results showed that the correlation coefficients between each morphological trait and body weight were all in significant or very significant difference levels. The path coefficients of the body length, carapace length, carapace width and first abdominal segment length of five-month-old F. chinensis to the body weight had all reached a level of significance, and the determination coefficients of body weight, total length and carapace length were very big. The path coefficients of carapace length, carapace width, carapace height, sixth abdominal segment length and fourth abdominal segment length of six-month-old F. chinensis to the body weight had all reached a level of significance, but the direct effect of fourth abdominal segment length to the body weight was negative. The diversification of determination coefficients was consistent with that of path coefficients. The attributes reached a level of significance were used to established the multiple regression equations, which were Y=-37.429+0.326X2+0.306 X3+0.669 X10+0.275 X14 and Y=-38.556+0.668 X2-0.583 X6+0.605 X8+0.785 X10+0.931 X12, respectively.2. Five consecutive selected populations and wide population of F. chinensis were amplified by 8 microsatellites. A total of 69 alleles were generated at 8 assessed loci, and the number of alleles per locus ranged from 5 to 15. On the average, each locus had detected 8.625 alleles. Polymorphic information content (PIC) varied from 0.606757 to 0.882644, and the average observed heterozygosity (Ho) of six populations were 0.7660, 0.7530, 0.7375, 0.7578, 0.7583, 0.6717, respectively. Compared with wide population, the average observed heterozygosity of cultured populations were decreased, but the observed heterozygosity of all populations had a high level. Fis valus showed that 10 cases of severe observed heterozygosity deficiency and 5 cases of severe observed heterozygosity excess were observed in all populations. As far as the total populations were concerned, the observed heterozygosity deficiency occurred at all of the loci tested. Pair-wise Fst values (<0.05), similarity coefficients and genetic distances among six populations suggested low genetic differentiation between six populations. The genetic diversity among six populations was relatively abundance, and there is potentiality for further selecion.3. AFLP technique was used to analyze genetic diversity and genetic differentiation of wild population and 2 consecutive selected populations of shrimp F. Chinensis. The genetic polymorphism, genetic distances and differentiation index were calculated according to the AFLP results. The results showed that 137 bands were generated with 5 primer sets, and 63 bands were polymorphic bands. On the average, each primer set had detected 12.6 polymorphic bands. The proportions of polymorphic loci were 45.99%, 40.57% and 41.04%, and the genetic diversities of wild population and the selected populations quantified by Shannon index were 0.1818, 0.1807 and 0.1774, respectively. The genetic distances and differentiation index between wild population and selected populations were large but which were very small between the ninth generation and the tenth generation of selected populations, 0.0031 and 0.0206 respectively. According to the results, with the increasing of selected generation, the selected populations showed that genetic distances and genetic differentiation became smaller, and that there was a convergence phenomena .This new variety had genetic stability.