Genetic determination of sex and shell color in the Pacific abalone Haliotis discus hannai revealed by an integrated linkage map.

Abstract

Integrated linkage maps for each sex have been constructed for the Pacific abalone Haliotis discus hannai using three F1 mapping families based on co-dominant markers. A total of 273 markers were placed on the female map, spanning 927.3cM with an average interval of 3.64cM, whereas 277 markers were mapped on the male map, covering 727.0cM with an average spacing of 2.80cM. Both female and male maps consisted of 18 linkage groups, corresponding well with the number of chromosomes. Furthermore, the sex-determining locus and the green/orange shell color controlling locus were mapped to the linkage group 3 (LG3) and LG9 respectively. A marker completely linked to phenotypic sex was identified, and the sex determination system was further concluded as paternal heterogametic (males XY and females XX). Based on the segregation ratio of the shell color in the progeny, a simple recessive model of epistasis was proposed to explain the distribution of different color morphs (green, orange and blue): the recessive allele determining orange type masks the effect of the locus controlling green and blue types, whereas the dominant allele at the green/orange locus permits the expression of green and blue types controlled by another locus. The current consensus map provides a useful framework for genetic studies in the Pacific abalone. Mapping of the sex-determining locus and the shell color-controlling locus leads to further understanding of the mechanisms underlying these important traits.