Marker-aided selection in a backcross breeding program for resistance to chestnut blight in the American chestnut

Abstract

Marker-assisted selection in backcross breeding is discussed in general and with specific reference to obtaining resistance to chestnut blight in American chestnut (Castaneadentata (Marsh.) Borkh.). Resistance from Chinese chestnut (Castaneamollissima Blume) is thought to be controlled by two unlinked codominant genes. Hybrids and backcross generations are available that would allow (i) the identification of DNA markers that linked to the resistance and (ii) the development of a genetic linkage map for the genome. These markers are codominant. Markers that are linked to the resistance genes would permit detection of the different genetic classes of resistance that may have similar phenotypes. Linked markers also provide the ability to identify individuals with a maximum amount of recombination surrounding the resistance loci thereby eliminating unwanted linked donor genetic material. Having molecular markers scattered throughout the genome would allow general selection against the background donor genome. This can reduce the number of backcross generations required to obtain individuals with the phenotype of C. dentata but with the blight resistance of C. mollissima. Methods are presented for the development of a set of random genomic markers.