Comparative Research Of Genetic Characterization In Acanthopagrus Schlegelii,Pagrus Major And Their Hybrid Offsprings

The morphological variations between Pagrus major,Acanthopagrus schlegelii and the reciprocal F1 hybrids(Pagrus major?×Acanthopagrus schlegelii?,and Acanthopagrus schlegelii?×Pagrus major?)were studied by four methods of multivariate analysis(variance analysis,cluster analysis,discriminant analysis and principal component analysis),based on their morphological characterizations including countable morphological parameters,meristic parameters and truss framework parameters.The result showed significant differences between Acanthopagrus schlegelii and Pagrus major in the number of scales above the lateral line,scales beneath the lateral line,spines of the dorsal fin,soft rays of the dorsal fin and the anal fin;Pagrus major?×Acanthopagrus schlegelii?and Pagrus major showed significant differences in the number of scales above the lateral line,scales beneath the lateral line,spines of the dorsal fin,soft rays of the dorsal fin and pectoral fins;Pagrus major?×Acanthopagrus schlegelii?and Acanthopagrus schlegelii showed significant differences in the number of scales above the lateral line,scales beneath the lateral line,anal fin and pectoral fins;Acanthopagrus schlegelii?×Pagrus major?and Pagrus major showed significant differences in the number of scales above the lateral line,scales beneath the lateral line,spines of the dorsal fin,soft rays of the dorsal fin and pectoral fins;Acanthopagrus schlegelii?×Pagrus major?and Acanthopagrus schlegelii showed significant differences in anal fin and pectoral fins.The discriminant functions of the four stocks were established,and the discriminatory accuracies were 100%(Pagrus major),83.3%(Acanthopagrus schlegelii),96.7%(Pagrus major?× Acanthopagrus schlegelii?)and 90.0%(Acanthopagrus schlegelii?× Pagrus major?),respectively.The total discriminatory accuracy was 92.5%.In the principal component analysis,eight principal components were constructed,and the cumulative contributory ratio was 72.72%,they are overlapped in scatter diagram.Morphological characteristics of Acanthopagrus schlegelii?×Pagrus major?were most similar with Acanthopagrus schlegelii on the basis of cluster analysis.The above results showed that the reciprocal hybrids resembled their parents in the morphological traits.The microsatellite sequences(simple sequence repeats,SSR)and codon bias in the coding regions(CDS)of Acanthopagrus schlegelii,Pagrus major,and their offsprings(orthogonal and reciprocal ones)were analyzed and compared using the method of bio-informatics.The results were as follows.The microsatellite sequences were mainly composed of the three-base repeat type,followed by the two-base repeat,and the most fragment length of repeat sequences were ranging from 12 bp to 20 bp.The black porgy and the reciprocal cross(Acanthopagrus schlegelii?×Pagrus major?)have the same dominant primitive type in the three and five bases,and the red porgy and the orthogonal(Pagrus major?×Acanthopagrus schlegelii ?)dominant base types in the three bases as well,while the black porgy and the orthogonal were the same in the four bases.Twenty-eight pieces of genetic codons such as UUC and UAC were the preferred codons in gene coding regions of the four sea bream species,preferring to use the codons ended in C or G,and the GC content of the third codon base(GC3s).Both were higher than the average GC content of the coding region of the gene.Eleven microsatellite loci and COI sequence were used to investigate genetic divergence and structure in Acanthopagrus schlegelii,Pagrus major and the reciprocal F1 hybrids(Pagrus major?× Acanthopagrus schlegelii?,and Acanthopagrus schlegelii?×Pagrus major?)populations.The number of alleles ranged from 3 to 15 at each locus of all samples.The observed heterozygosity(Ho =0.658)and Polymorphism Information Content(PIC=0.578)of Pagrus major?×Acanthopagrus schlegelii?were higher than their parents(Acanthopagrus schlegelii Ho = 0.642,PIC=0.575 and Pagrus major Ho = 0.610,PIC=0.507),the number of effective alleles(Ne: 3.172)ranged from Acanthopagrus schlegelii(3.383)to Pagrus major(2.970).The effective number alleles(3.192),observed heterozygosity(0.657)and polymorphism information content(0.573)of Acanthopagrus schlegelii?×Pagrus major?were all similar to Acanthopagrus schlegelii.The highest genetic similarity(0.9297)and the lowest genetic distance(0.0729)were found between Acanthopagrus schlegelii?×Pagrus major?and Acanthopagrus schlegelii.The genetic distances between Pagrus major?× Acanthopagrus schlegelii? and Acanthopagrus schlegelii similar to that between Pagrus major?×Acanthopagrus schlegelii? and Pagrus major were 0.4386 and 0.4459,respectively.Pagrus major?×Acanthopagrus schlegelii? inherited genetic material from both parents,whereas Acanthopagrus schlegelii?× Pagrus major? only inherited maternal genetic material,indicating gynogenetic progeny.In addition,37 haplotypes(Hap 1-Hap 37)were defined in all samples by COI sequences,in which 2 haplotypes(Hap 11 and Hap 13)were shared among Pagrus major?×Acanthopagrus schlegelii ? and Acanthopagrus schlegelii,1 haplotypes(Hap 2)were shared among Pagrus major?×Acanthopagrus schlegelii ? and Pagrus major,and 5 haplotypes(Hap 10,Hap 11,Hap 12,Hap 14 and Hap 15)were shared among Acanthopagrus schlegelii?×Pagrus major? and Acanthopagrus schlegelii.The most haplotype diversity(0.997),most nucleotide diversity(0.016)and most average number of nucleotide differences(10.878)were detected in Acanthopagrus schlegelii,lowest of Pagrus major?×Acanthopagrus schlegelii?(0.924,0.005,3.262),Acanthopagrus schlegelii?×Pagrus major?(0.996,0.007,4.853)were between Acanthopagrus schlegelii and Pagrus major(0.995,0.006,4.244).It could be concluded that the genetic diversity of Acanthopagrus schlegelii?×Pagrus major? resembled Acanthopagrus schlegelii.