Marker-Assisted Recurrent Backcrossing in Cultivar Development

Abstract

Marker-assisted recurrent backcrossing (MARS), the combined use of marker-assisted selection (MAS) and recurrent backcrossing, is a versatile method for plant breeding and genetic studies. The benefits of MARS are well demonstrated and documented in theoretical and simulation studies, and confirmed by empirical applications. In MARS, markers are used during recurrent backcrossing to select for the presence of the target gene (foreground selection), to select against the donor genome contribution (background selection) to reduce the introgressed segment's size and thus potential linkage drag. MARS reduces the number of backcrossing needed to recover most of the recurrent parent genome in 3-4 generations, while one or two target genes are introgressed from the donor. For foreground selection markers are most useful for traits that are expensive and/or difficult to measure. Linkage drag associated with the target genets), when present, is difficult if not impossible to remove by phenotypic selection. In this chapter, we summarised some of the theoretical and simulation results of MARS, and provided comprehensive summary of the use of MARS in practical crop breeding.