Efficient integration of molecular and conventional breeding methodologies

Abstract

Molecular markers make it possible for breeders to combine desirable alleles at a greater number of loci and at earlier generations than is possible with conventional breeding methodologies. With an increasing number of markers for important traits, marker assisted selection (MAS) strategies that minimize population sizes and assay numbers while ensuring important alleles are not lost become increasingly important. In practical breeding, strategies will often have to balance MAS with the need to retain variability for important traits that are selected partly or wholly by conventional means This paper will discuss strategies to maximize the number of traits that can be combined in a single breeding cycle taking account of practical limits such as reasonable population sizes that can be managed in a breeding program. Examples from our breeding program and mapping populations will be used to illustrate the effects of different MAS strategies on population size and levels of residual genetic variation at unselected loci. It is these unselected loci that become important where conventional selection follows MAS