Genetic gain with desired status number in breeding programs: a study on selection effects

Genetic gain and average coancestry or status number was investigated for f ive selection methods: penalty index selection (PIS), family index selectio n (FIS), combined between-family and within-family selection (CBW), restric ted individual selection (RIS), and combined index selection (RCS). PIS was a function of an individual's breeding value and family contributions, mod elled as a stepwise procedure to select superior individuals one by one. A penalty would indicate the need to have low average coancestry or large sta tus number. Breeding populations of unrelated families were investigated by Monte Carlo simulation to examine the genetic response of the five selecti on methods at a restricted selection intensity and average coancestry. PIS attained the greatest genetic gain, except at the selection limits of maxim um genetic gain and minimum average coancestry where PIS might be identical to the other selection methods. FIS and RCS well approximated PIS at high average coancestry. RIS was similar to RCS when the heritability was high, particularly at low average coancestry. CBW attained the least genetic gain among the selection methods. For all selections, high heritability would c ontribute to a greater genetic gain and status number or low average coance stry. PIS was applied to a practical breeding program in Alberta that inclu ded several subpopulations. The results suggested that the selection effici ency for balancing genetic gain and average coancestry would increase when deploying a subpopulation strategy for breeding population management.