Structure of the mitochondrial DNA control region of the sinipercine fishes and their phylogenetic relationship.

The mitochondrial DNA control region of Siniperca chuatsi, S. kneri, S. scherzeri, S. obscura, S. undulata, Coreosiniperca roulei and Coreoperca whiteheadi were amplified by PCR amplification and directly sequenced. The mtDNA control region of the sinipercine fishes could be separated into three domains, namely, the terminal associated sequence domain, the central conserved sequence domain and the conserved sequence block domain. The extended terminal associated sequence (ETAS), three conserved sequence blocks (CSB-F, CSB-E, CSB-D) in the central conserved sequence domain and three conserved sequence blocks (CSB1, CSB2, CSB3) in the conserved sequence block domain were also identified. The phylogenetic relationships among these sinipercine fishes were constructed through neighbor-joining and maximum parsimony methods using Percidae and Serranidae as outgroups. Results showed that sinipercine fishes were a monophyletic group, with Siniperca forming one group, and Coreoperca forming another group. Coreosiniperca roulei did not form an independent group but was merged into the genus Siniperca. Thus it should be renamed as Siniperca roulei.

Microsatellite analysis of variation among wild, domesticated, and genetically improved populations of blunt snout bream (Megalobrama amblycephala).

In the present study, the genetic diversity of one selected strain (Pujiang No. 1), two domesticated populations (GA and HX) and four wild populations (LZ, YN, SS and JL) of blunt snout bream (Megalobrama amblycephala) was analyzed using 17 microsatellite markers. The results showed that an average of 4.88-7.65 number of alleles (A); an average of 3.20-5.33 effective alleles (Ne); average observed heterozygosity (Ho) of 0.6985-0.9044; average expected heterozygosity (He) of 0.6501-0.7805; and the average polymorphism information content (PIC) at 0.5706-0.7226. Pairwise FST value between populations ranged from 0.0307-0.1451, and Nei's standard genetic distance between populations was 0.0938-0.4524. The expected heterozygosities in the domesticated populations (GA and HX) were significantly lower than those found in three wild populations (LZ, SS and JL), but no difference was detected when compared with the wild YN population. Likewise, no difference was found between the four wild populations or two domesticated populations. The expected heterozygosity in Pujiang No. 1 was higher than the two domesticated populations and lower than the four wild populations. Regarding pairwise FST value between populations, permutation test P-values were significant between the GA, HX and PJ populations, but not between the four wild populations. These results showed that the expected heterozygosity in the selected strain of blunt snout bream, after seven generations of selective breeding, was lower than that of wild populations, but this strain retains higher levels of genetic diversity than domesticated populations. The genetic differences and differentiation amongst wild populations, domesticated populations and the genetically improved strain of blunt snout bream will provide important conservation criteria and guide the utilization of germplasm resources.

Possible genetic reproductive isolation between two tilapiine genera and species: Oreochromis niloticus and Sarotherodon melanotheron.

Successful crossbreeding between Oreochromis niloticus and Sarotherodon melanotheron to produce a commercial hybrid has been difficult. The karyotypes and isoenzyme of these two species and their reciprocal hybrids (O. niloticus female × S. melanotheron male, S. melanotheron female × O. niloticus male, the last not included in the isoenzyme study) were investigated via metaphase chromosomes obtained from head kidney cells and electropherogram of lactate dehydrogenase (LDH) isoenzymes from the liver, kidney, white muscle, heart, and eye balls. The diploid chromosome number (2n=44) and the fundamental number (NF=50) of the four tilapia genotypes were the same. However, the karyotype of O. niloticus had three pairs of sub-metacentric (sm), twelve pairs of sub-telocentric (st), and seven pairs of telocentric (t) chromosomes, while S. melanotheron had one pair of metacentric (m), two pairs of sm, 12 pairs of st, and seven pairs of t chromosomes. The reciprocal hybrids both showed a mixed karyotype range between their parents: 0.5 pair of m, 2.5 pairs of sm, 12 pairs of st, and seven pairs of t chromosomes. In view of the electropherogram of isozymes, only the LDH of the kidney showed significant clear bands, with five bands in O. niloticus, three bands in S. melanotheron, and duplicated six bands in the hybrids. The bands varied depending on their activities and mobilities. We considered that the differences in karyotype and isoenzyme were related to the genetic mechanism for post-mating isolation, and provided some additional basic genetic background of their taxonomy.

RAPD-SCAR Markers for Genetically Improved NEW GIFT Nile Tilapia (Oreochromis niloticus niloticus L.) and Their Application in Strain Identification.

The NEW GIFT Nile tilapia (Oreochromis niloticus niloticus L.) is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety has been extended in most of areas of China. The management of genetically improved strains, including the genetic markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S(304 )(624 bp ) and S(36 )(568 bp ) were identified. The strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains worldwide. The frequency of SCAR marker I (553 bp) was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain. The frequency of SCAR marker II (558 bp) was 91.4% in NEW GIFT Nile tilapia, but 0% - 70% in the 7 other strains. In order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt, resulted the frequency of SCAR I and II was 10% and 70%, respectively, much lower than that of New GIFT strain. The increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the quantitative trait loci (QTL) underlining the performance traits by long term selection, and indicate the bright potential of SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically improved strain and other strains.

Development of microsatellite markers for blunt snout bream Megalobrama amblycephala using 5'-anchored PCR.

A rapid method for isolating microsatellite loci in blunt snout bream, based on the 5'-anchored polymerase chain reaction technique, revealed 522 microsatellite loci (consisting of 442 dinucleotide, 4 trinucleotide and 76 tetranucleotide repeats). Of the 25 loci characterized, 10 turned out to be highly polymorphic. The number of alleles per locus ranged from 3 to 17 while the expected heterozygosity ranged from 0.4899 to 0.9355 in population of selected strain F(7 ) and from 0.5786 to 0.9556 in wild population from Lake Liangzi. These markers are useful as tools for the detection of genetic variation levels in selected strains and wild populations of blunt snout bream for germplasm conservation.

Isolation and characterization of polymorphic microsatellite markers from Australia short-finned eel (Anguilla australis Richardson).

Seventeen microsatellite DNA loci from the Australian short-finned eel (Anguilla australis Richardson) were isolated and their amplification characteristics were described. The polymerase chain reaction primers were tested on 40 eel individuals. The primers amplified loci with relatively high numbers of alleles, ranging from five to 14 with an average of nine per locus. Mean observed heterozygosity (H(O) ) and expected heterozygosity (H(E) ) were 0.6779 and 0.7374, respectively, indicating that these markers would be useful for population studies. No loci deviated significantly from Hardy-Weinberg equilibrium (P = 0.05) and no evidence was found for genotypic disequilibrium among loci at a 5% significance level.