Marker-Assisted Breeding in Higher Plants

Abstract

The deployment of DNA-based marker systems promises to accelerate the improvement of crop productivity worldwide. Numerous DNA fingerprinting assays, and more recently whole genome sequence information, have been utilized extensively for employing intrinsic genetic polymorphisms in the genomes of higher plants in phylogenetic studies, genetic mapping, and comparative genomic analysis. DNA markers set the stage for initiating genomic-based breeding strategies with several advantages over the phenotypic based selection procedures used in conventional breeding programs. In maize, successful applications have been exemplified by marker assisted introgression of novel genomic regions associated with anthesis-silking interval, marker-based diagnosis of plants containing the opaque2 gene associated with quality, and marker-based prediction of hybrid vigor. New rice varieties are developed using DNA markers associated with genes and quantitative trait loci (QTLs) to provide resistance to both biotic stress, e.g. bacterial blight and blast, and abiotic stresses, and to improve yield and quality. A wheat variety `Patwin' was developed through marker assisted selection for stripe and leaf rust resistance genes Yr17 and Lr37, respectively. The stay-green trait conferring resistance to drought in sorghum has been explored at length. In tomato, cotton, potato, soybean and other crops, many genes conferring resistance against various biotic stresses have been incorporated from wild relatives using DNA markers. Wider adaptation of marker assisted breeding is limited by the narrow genetic base of elite gene pools for many plants. Multiple investigations reveal conservation of QTLs among some crop species, offering opportunities to gain information from one crop to improve others.