Predicted genetic gain and inbreeding depression with general inbreeding levels in selection candidates and offspring
Methods for predicting response to selection in noninbred populations for individuals and family-based selection methods have been very well developed. However, theory to predict improvement of inbred lines derived from a recombined population, as well the predicted change in inbreeding depression rate, has not been developed. Prediction equations for general levels of inbreeding in both selection candidates and recombined offspring of selected parents for intrapopulation selection methods were developed. All common methods of individual, half-sib, and self-progeny selection were predicted to change inbreeding depression rates in a population if the covariance parameters D1 and D2* were nonzero. However, the change in inbreeding depression rate was unaffected by additive genetic variance. It was further established that outbred selection in some maize (Zea mays L.) populations may be expected to increase inbreeding depression based on published estimates of the covariance parameter D1.