Genetic Linkage Map Construction And QTL Analysis For Growth-related Traits In The Pacific Abalone

Preliminary genetic linkage maps were constructed for the Pacific abalone (Haliotis discus hannai Ino) using AFLP, RAPD and microsatellite markers segregating in a F1 family. Eight microsatellite loci, 41 RAPD and 2688 AFLP markers were genotyped in the parents and 86 progeny of the mapping family. Among the 2737 markers, 383 (including 365 AFLP markers, 10 RAPD markers and 8 microsatellite loci) were polymorphic and segregated in one of the parents: 241 in the female and 146 in the male (including part of same micosatellite loci). With the sequential Bonferroni correction, the majority of these markers, 232 in the female and 134 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. The female framework map was composed of 119 markers in 22 linkage groups, covering 1773.6 cM with an average interval of 18.3 cM. The male framework map contained 94 markers in 19 linkage groups, spanning 1365.9 cM with an average marker density of 18.2 cM. The sex determination locus was mapped to the male map but not the female map, suggesting a XY-male determination mechanism. Distorted markers showing excess of homozygotes were mapped in clusters probably because some genes between two abalones were incompatible. The map locations and effects of quantitative trait loci (QTL) were estimated for nine growth-related characters in Pacific abalone based on the female and male genetic maps. Twenty-eight putatively significant QTL (LOD >2.4) were detected for nine characters. The percentage of phenotypic variation explained by a single QTL ranged from 8.0 to 35.91%. The significant correlations (p<0.001) were found among all the traits, Pearson correlation coefficients were more than 0.81. Four QTL were identified for shell length and shell width on the J3, J12, J19 and C9 linkage groups. Two QTL were identified for total weight on the J1 and C1 linkage maps. There only one QTL was detected for shell weight which existed on the J15 linkage group. For soft weight, there totally four QTL were detected and distributed on the J4, J5, C1 and C7 linkage group. Three QTL for muscle weight were identified on the J4 and C1 linkage map, on the J4 linkage which had two QTL. Four QTL were identified for gonad and digestive gland weight which distributed on the J1, J5, J10 and C9. For mantle weight, five QTL were detected on the J4, C1, C9 and C12 linkage maps. Two QTL were detected for gill weight on the J1 and C9. The QTL for growth-related characters clustered on the 11 linkage map, which means these growth-related characters shared the common genetic elements. Genetic linkage map construction and QTL analysis for growth-related traits which construction the base for the marker-assisted selection and will eventually improve genetic base of the Pacific abalone.