Applications of Quantitative Genetic Theory in Plant Breeding Selection Methods in Plant Breeding

In the preceding chapters dealing with traits with quantitative variation, a number of important concepts were introduced, such as phenotypic value and genotypic value (Chapter 8), expected genotypic value (Chapter 9) and genotypic variance (Chapter 10). The present chapter focusses on applications of these concepts that are important in the context of this book. Thus the response to selection, both its predicted and its actual value, is considered. The prediction of the response is based on estimates of the heritability. Procedures for the estimation of this quantity are elaborated for plant material that can identically be reproduced (clones of crops with vegetative reproduction, pure lines of self-fertilizing crops and single-cross hybrids). It is shown how the heritability value depends on the number of replications. In addition to the partitioning of the genotypic value in terms of parameters defined in the framework of the F∞-metric (Section 8.3.2), or in terms of additive genotypic value and dominance deviation (Section 8.3.3), here the rather straightforward partitioning in terms of general combining ability and specific combining ability is elaborated.