Genetic Diversity Analysis And Genetic Linkage Map Construction In The Pacific Abalone (Haliotis Discus Hannai)

In this study, the genetic structure and genetic diversity of cultured and wild Pacific abalone Haliotis discus hannai were analyzed using AFLP technique on the basis of investigation of the inheritance mode of AFLP markers, and genetic linkage maps of female and male H. discus hannai were constructed with AFLP and microsatellite markers, using their full-sib family with F1 progeny.A total of 115 individuals from three families (♀467×♂447,♀467×♂431,♀570×♂431) of H. discus hannai were employed in the inheritance study. For the 119 cases at 45 marker-loci generated by one AFLP primer pair, observed segregation ratios were estimated with 95% C.I., and compared with expected Mendelian segregation ratios. In each case, only one of the two possible expected ratios was accepted in all markers, furthermore, no significant deviation from Mendelian inheritance (two-tailed binomial test, P≥0.053).To investigate the polymorphism of AFLP markers, and the genetic diversity in populations of H. discus hannai, eight abalone populations were analyzed by using a total of six AFLP primer combinations. The mean percentages of polymorphic loci of the eight populations were 48.65% (DLC), 50.50% (YTC), 51.17% (JNC), 50.51% (LSC), 58.90% (CDW), 60.07% (LDW), 68.92% (JPW) and 54.05% (DLW), respectively. The expected heterozygosities (He) of them were 0.2291, 0.2438, 0.2442, 0.2374, 0.2626, 0.2723, 0.3137 and 0.2802, respectively. The cultured abalone populations exhibited lower levels of polymorphisms and heterozygosities than the wild ones. Fst values were obtained in pairwise comparison of populations, with an average of 0.036. Genetic identities among the eight populations ranged from 0.9623 to 0.9886, and genetic distances were between 0.0115 and 0.0385. The UPGMA dendrogram constructed on the basis of the distances showed that the eight populations were allocated into two major groups, that is, one group including the four cultured populations, and the other group consisting of the four wild populations.Fifty-five microsatellite loci and 484 AFLP markers which were genotyped in the parents and 88 progeny of the mapping family were polymorphic and segregated in one of the parents: 267 in the female and 275 in the male (including part of same microsatellite loci). With the sequential Bonferroni correction, the majority of these markers, 260 in the female and 265 in the male, segregated according to the expected 1:1 Mendelian ratio (P≥0.05). Two genetic linkage maps were constructed using markers segregating in the female or the male parent, excluding the distorted segregating ones. The female framework map was composed of 220 markers in 20 linkage groups, covering 2733.8 cM with an average interval of 13.7 cM. The male framework map contained 248 markers in 19 linkage groups, spanning 2860.2 cM with an average marker density of 12.5 cM. The observed coverage was 83.4% for the female map and 85.8% for the male map. The comparison between female and male map of H. discus hannai with microsatellite markers showed 10 pairs of homologous linkage groups.