Use of Random Amplified Polymorphic DNA Markers in Breeding for Major Gene Resistance to Plant Pathogens

Abstract

Markers are of interest to plant breeders as a source of genetic information on crops and for use in indirect selection of traits linked with the markers. Selection based on the marker would be more efficient provided there was tight linkage between the marker and the trait of interest [<5 centimorgans (cM)] and assuming selection for the marker was more convenient (faster, cheaper, reproducible, expressed earlier). Markers for disease resistance offer the additional advantage of permitting selection for resistance in the absence of the pathogen or a variant of the pathogen. This feature is of particular interest to a plant breeder who may be reluctant either to work directly with or to introduce a pathogen where quarantine restrictions prevent its introduction. Markers linked to various resistance genes would greatly facilitate breeding for multiple disease resistance, since selection based on markers could be readily incorporated into a breeding program. This approach would be of particular interest with pathogens that exhibit inconsistent expression due to environmental or other factors. A single technology that would indirectly permit selection for diverse disease resistance genes would be highly desirable and extremely useful in breeding for disease resistance. Indirect selection as an efficient and practical means of developing disease-resistant cultivars will depend on the identification of markers that are easy to score and tightly linked to different resistance genes.