Quantitative genetics in an apple breeding strategy

Open-pollinated seed of 500 genotypes of commercial cultivars, breeding selections and wild species of apples (Malus x domestica) was collected from overseas mixed-clone repositories. This is to generate the first generation of the new 'Apple Breeding Population'. Subsequent generations will be intercrossed in a pair-crossing design. Recurrent selection for general combining ability (GCA) is the breeding method used for genetic improvement of the Breeding Population. Every parent in the control-pollinated breeding population is tested for GCA using a polycross mating design. The best individuals of the Breeding Population, intensively selected between families using the polycross GCA estimates, and also within families are intermated to produce a 'Cultivar Production Population'. Trees selected from this have then to be evaluated in grafted clonal tests before commercial release. Each generation, a new Breeding Population of 500 genotypes is selected from the pair-cross families, based on parental GCA values (from polycross tests), full-sib family means and individual performance and then intercrossed. Greatest emphasis will be on within-family selection not between-family, so as to avoid reducing the effective population size.