MARKER ASSISTED SELECTION IN DISEASE RESISTANCE BREEDING

Abstract

Feeding ever-increasing population is the main challenge faced by the agricultural scientists and to meet this plant breeders have to put continuous efforts to develop new crop varieties on fast track basis. DNA based polymorphism, commonly known as DNA markers can be used for genetic improvement through selection for favourable traits such as disease resistance. Molecular markers are becoming an essential component in backcross breeding programs for tracking the resistance genes in gene pyramiding. Marker assisted selection (MAS), is expected to increase genetic response by affecting efficiency and accuracy of selection. Even though marker-assisted selection now plays a prominent role in the field of plant breeding, examples of successful, practical outcomes are rare. MAS, with few exceptions, has not yet delivered its expected benefits in commercial breeding. It is clear that DNA markers hold great promise, but realizing that promise remains elusive. The economic and biological constraints such as a low return of investment in small-grain cereal breeding, lack of diagnostic markers, and the prevalence of QTL-background effects hinder the broad implementation of MAS. Until complex traits can be fully dissected, the application of MAS will be limited to genes of moderate-to-large effect and to applications that do not endanger the response to conventional selection. Till then, observable phenotype will remain an important component of genetic improvement programmes, because it takes in to account the collective effect of all genes. In future, chip-based, high-throughput genotyping platforms and the introduction of genomic selection will reduce the current problems of integrating MAS in practical breeding programs and open new avenues for a molecular-based resistance breeding.