Study On Population Genetic Diversity Of Culter Alburnus And Phylogeny Of Cultrinae

Morphological variations, muscle nutritional quality and genetic divergence of different populations of the topmouth culter (Culter alburnus (Basilewsky)) and molecular phylogeny of Cultrinae were analyzed in the dissertation. There were four major parts, listed as follow:1 Analysis of morphological variations among seven populations of the topmouth culterThe morphological variations among seven populations of the topmouth culter were analyzed using three multivariation analysis methods based on 31 proportional parameters of morphometric characters, which were collected respectively from Nan Wan Reservoir (NW), Taihu Lake (TH), Xingkaihu Lake (XKH), Liangzihu Lake (LZH), Fuqiaohe Reservoir (FQH), Sanxikou Reservoir (SXK) and the artificial cultured population of Huzhou, Zhejiang province (CP). The results of cluster analysis revealed that the seven populations were clustered into three clades. The first group included populations of XKH, TH, NW and CP; LZH and SXK populations were clustered as the second group; the third group was the FQH population alone. Principal component analysis showed that the contribution of the length of head and tail to total variances were the most among the 31 proportional parameters metric characters and truss network. Discriminant analysis indicated that the identification accuracy of the discriminant functions of these populations were 73.333%-100%(P1) and 81.481%-100%(P2), and the total discriminant accuracy was 90%. All results showed that there were some differences to a certain extent among the seven populations of the topmouth culter and the seven populations could be identified using three multivariation analysis methods.2 Comparative study on muscle nutritional quality of six different geographical populations of the topmouth culterExperiments were conducted to compare the nutritional quality in the muscles ofthe topmouth culter among six populations, which were collected from Taihu Lake, Xingkaihu Lake, Liangzihu Lake, Nanwan reservoir, Fuqiaohe reservoir and pond in Taihu Lake region. The results showed that significant differences were not observed in moisture, ash and crude protein contents in muscles of the six experimental populations (P>0.05), while muscle lipid content of farmed population was significantly higher than those of other five wild populations (P<0.05). The level of polyunsaturated fatty acids and essential fatty acids contents of population of Nanwan reservoir were the highest. The order of the contents of essential was: population of Nanwan reservoir > Fuqiaohe reservoir > Xingkaihu Lake > Langzihu Lake > farmed population >Taihu Lake. The order of total amino acids contents of experimental populations was: Taihu Lake > Xingkaihu Lake > Nanwan reservoir > Langzihu Lake > Fuqiaohe reservoir > farmed population, and for contents of essential amino acids, it was Taihu Lake > Xingkaihu Lake > Langzihu Lake > Nanwan reservoir > Fuqiaohe reservoir > population farmed, while for Essential Amino Acid Index (EAAI), it was: population of Taihu Lake > Nanwan reservoir > Langzihu Lake > Xingkaihu Lake > Fuqiaohe reservoir > fanned population. The majority of Amino Acid Score (AAS) and Chemical Score (CS) of essential amino acids were higher than 1, except for lysine, phenylalanine and tyrosine for Xingkaihu Lake population. However, for the farmed population, many CS of amino acids were lower than 1. In conclusion, the flesh quality of the wild populations was prior to the fanned population, and the populations of Taihu Lake, Xingkaihu Lake and Nanwan reservoir were much better among the wild population.3 Assessing genetic diversity of populations of the topmouth culter in China using molecular markersThe genetic structure and diversity of populations of topmouth culter in China were assessed by using AFLP, ISSR, COII and D-LOOP sequences and the validity of the molecular markers were compared in this part. The study indicated that the genetic diversity of the topmouth culter was high and had a complex genetic structure. The genetic diversities of XKH, NW and TH populations were higher than the other populations. The distribution of the topmouth culter in China could be divided into two major parts, the northern and southern region between which it took on great differentiation of the genetic variation. The XKH, NW and TH populations belonged to the northern region, and SXK and LZH populations were included in the southernregion. In addition, our results showed that the AFLP was superior to ISSR because it can provide enough polymorphic loci to analyze the population genetics of the topmouth culter. Both COII and D-LOOP sequences could provide some information of genetics, however, the D-LOOP was better than COII, because the speed of evolution of D-LOOP was quicker than COII and it contained much more variable sites. Therefore, AFLP and D-LOOP sequences were used to analyze the genetic differentiation between the wild and cultured populations of the topmouth culter. A total of 373 reproducible bands amplified with seven AFLP primer combinations were obtained from 50 fish. The average percentage of polymorphic loci was 44.12%. The cultured population appeared to have a lower level of polymorphism (37%) than the wild population (51.21%). Analysis of molecular variance (AMOVA) inferred from D-LOOP revealed that degree of genetic divergence was not large (Fs7=0.08, P< 0.01). Our data argued that genetic drift, gene flow, and stochastic introduction events were the possible factors influencing the population structure and genetic variation.4 Molecular phylogeny of the Cultrinae inferred from mitochondrial DNA control region sequencesThe molecular phylogeny of Cultrinae was analyzed using D-LOOP sequences, using Cyprinus carpio and Ctenopharyngodon idella as outgroup. In the MP and NJ tree, the samples of Culter blended with that of Cultrichthys, Culter alburnus, Culter recurviceps and Culte dabryi were clustered first, and then, Culter mongolicus, Culter oxycephaloides and Cultrichthys erythropterus were clustered, and these two major clades composed one group. Then, Megalobrama, Sinibrama, Parabramis and Hemiculter clustered in order. Cultrinae was divided into three major clades in BI tree. Culter and Cultrichthys were the first clade, Megalobrama, Sinibrama and Parabramis clustered as the second one, Hemiculter was the third clade. The above results indicated that there was closer relative relationship between Culter and Cultrichthys, and between Sinibrama and Parabramis had much closer relative relationship, too. The results agreed that Cultrinae was monophyletic group and did not agree with Culter was monophyletic group. And the same results were obtained by using Cyt b gene sequences. Our results indicated that the name of Erythroculter ilishaeformis should be Culter alburnus. In addition, ISSR and COII as the molecular identification markers were used to identify the Culter alburnus, Culter recurviceps, Culte dabryi and Cultrichthys erythropterus, the outcomes were beneficial to identifythese four culters.In this dissertation, it provided much basic data for future broodstock selection, constituting relevant management policy, protection the germplasm for the different populations of the topmouth culter, and increases the information of the phylogeny of Cultrinae, it also should be beneficial to further study on the phylogeny, origin and evolution of Cultrinae.