Abstract
A within-family marker-assisted selection scheme was designed for typical aquaculture breeding schemes, where most traits are recorded on sibs of the candidates. Here, sibs of candidates were tested for the trait and genotyped to establish genetic marker effects on the trait. BLUP breeding values were calculated, including information of the markers (MAS) or not (NONMAS). These breeding values were identical for all family members in the NONMAS schemes, but differed between family members in the MAS schemes, making within-family selection possible. MAS had up to twice the total genetic gain of the corresponding NONMAS scheme. MAS was somewhat less effective when heritability increased from 0.06 to 0.12 or when the frequency of the positive allele was < 0.5. The relative efficiency of MAS was higher for schemes with more candidates, because of larger fullsib family sizes. MAS was also more efficient when male:female mating ratio changed from 1:1 to 1:5 or when the QTL explained more of the total genetic variation. Four instead of two markers linked to the QTL increased genetic gain somewhat. There was no significant difference in polygenic genetic gain between MAS and NONMAS for most schemes. The rates of inbreeding were lower for MAS than NON-MAS schemes, because fewer full-sibs were selected by MAS.
Highlights
IntroductionMost traits are recorded on sibs of the candidates, because the timing of recording (fillet quality traits are measured after slaughter) or kind of recording (disease risk in case of a challenge test) make it impossible to measure these traits on the selection candidates
For aquaculture species, most traits are recorded on sibs of the candidates, because the timing of recording or kind of recording make it impossible to measure these traits on the selection candidates
The total genetic gain (∆Gtot) was 0.203 for marker-assisted selection (MAS) and 0.176 for NONMAS in generation two, i.e. the increase in total genetic gain (∆Gtot) was 15% higher for the MAS schemes compared with the NONMAS schemes in the first generation of selection with marker information
Summary
Most traits are recorded on sibs of the candidates, because the timing of recording (fillet quality traits are measured after slaughter) or kind of recording (disease risk in case of a challenge test) make it impossible to measure these traits on the selection candidates. The heritability of these traits is often low to medium (see [9] for a review). Kashi et al [11] presented a grand-daughter design for MAS schemes, in which a sire and his progeny-tested sons are genotyped and phenotypic information is collected on the grand-progeny as daughter group means. A two-generational design for a typical aquaculture breeding scheme will be presented
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