Genetic Identification And Analysis For Gynogenetic Diploids In Japanese Flounder Based On M-C Mapping

The Japanese flounder is marine precious economical fishes.Nowadays the Japanese flounder has been the the most importantbreeding species in Chinese coastal areas. Therefore the development ofgenetic improvement study and the cultivation of excellent family ofJapanese flounder of good economic traits have very important meaningto meet the needs of aquaculture industry accompanying with theinbreeding problemThe mature spawners selected from Japanese flounder selection andbreeding founder were used to produce the normal diploids (ND), meioticgynogenetic diploids (MGD-1), successive two generation meioticgynogenetic diploids (MGD-2) and inbred diploid (MGD-3) by crossingmature female from MGD-1with induced sex reversed male. A set of72microsatellite markers distributed evenly on24linkage groups wereselected from the published genetic linkage maps of Japanese flounder.To estimate microsatellite-centromere map distances, four MGD-1lineswere produced. Under the assumption of complete interference,17markers were located in the centromeric region,39in the telomericregion and19in the intermediate region of linkage groups. The geneticcharacteristics of four types of diploid in Japanese flounder wereidentified by these markers. Analysis showed that the number of allele (A)and polymorphism information content (PIC) have limited variation range, in which, the A and PIC of ND were the highest while those ofMGD-3were the lowest. In four types of diploid, the observedheterozygosity decreased and homozygosity increased asmicrosatellite-centromere map distance increased. The highest and lowestpercentages of homozygous individuals were found in centromeric regionfrom8.8%to29.1%and in telomeric region from2.4%to23.2%,respectively. In which, the variation range of MGD-1and MGD-2weresignificant higher than that of the rest diploids. Thus, choice ofmicrosatellite markers located on different positions in linkage grouphave greatly impact on identifying genetic characteristic of differentdiploids in Japanese flounder.A set of72microsatellite markers distributed evenly on24linkagegroups were selected from the published genetic linkage maps ofJapanese flounder (Paralichthys olivaceus). In two normal diploid full-sibfamilies, the test for Mendelian inheritance shows that genotypicsegregation deviations were not significant at all analyzed loci. Toestimate microsatellite-centromere (M-C) map distances, four meioticgynogenetic diploid lines were produced by the activation of eggs usingUV irradiated sperm of red sea bream (Pagrus major) and cold shocktreatment to block the extrusion of the second polar body. Under theassumption of complete interference,21markers were located in thecentromeric region,39in the telomeric region and the rest in the intermediate region of linkage groups. A total of192mitotic gynogeneticdiploids from one spawn were identified by these markers. Genotypeanalysis showed that the number of homozygous individuals decreased asM-C map distance increased on eachlinkage group.