Progeny testing - Genetic selection and hybridization in Aquaculture

Progeny testing

Progeny testing enables the assessment of the breeding qualities of separate spawners or pairs of spawners and the selection of the best for further selection work. However, progeny testing will increase the generation interval very markedly. For example, in carp breeding it requires one or two years, which would mean a slowing down of selection work by 20 to 30 per cent.

Three methods of progeny testing are applicable in aquaculture. The first method is testing of pairs, without testing males and females separately (fig. 8.4a). The second is to test spawners belonging to one sex, as for example females only as shown in fig. 8.4b, and the third is the testing of both females and males (complete diallele crossing) (fig. 8.4c).

The equation to measure selection response is the same as in family selection. Intensity of selection is limited by the number of families. Variability of family means (s_f) is also the same in both cases. Heritability of family means (h²_f) in progeny testing is high, as in family testing. This may occur only if the breeding conditions of all progenies are practically identical or if breeding proceeds with a three- or four-fold reiteration.

By comparing the response values in the two equations (R = Sh² and R_f = S_fh²_f), it should be possible to determine which method is more efficient in a given programme. If Sh² is greater than S_fh², mass selection is more effective than selection for relatives. The selection for relatives is only advantageous when the increase in heritability is not accompanied by a proportionally greater drop in the selection differential.