Marker-assisted selection will become the main direction of future breeding
Conventional breeding methods have limitations such as genetic variation and genome hybridization; in principle, these limitations can be overcome through genetic engineering methods (such as recombinant DNA). Using these methods, genes with defined functions can be cloned and introduced into different species in a rapid and highly specialized manner. Therefore, a wide variety of organisms have become sources of useful alleles, avoiding the mixing of entire genomes. At present, the basic limitation on the application of genetic engineering appears to be public acceptance of genetically modified organisms, which are obtained through gene cloning and transformation methods.
Conventional breeding methods have limitations such as genetic variation and genome hybridization,
In marker-assisted selection (MAS) breeding, plant breeders make use of the association between allelic variation in agronomic traits and genetic markers (mainly molecular markers). The general idea of marker-assisted breeding is that before breeders can use a linkage-based association between a trait and a marker, that association must be evaluated with some degree of accuracy, so that the marker genotype can be used as an indicator or predictor of the trait genotype and phenotype. Once the marker-trait association has been reliably evaluated, breeders can monitor the transmission of trait genes through closely linked markers, and therefore can carry out “genotype construction”, that is, through carefully planned crosses and selection, using marker genotypes as selection criteria, to construct the desired genotype.
More than 80 years ago, people had already recognized the potential value of genetic markers, linkage maps and indirect selection in plant breeding. Since the emergence of DNA marker technology in the 1980s, the efficiency of plant breeding has been significantly improved. Over the past 20 years or more, many breeding companies have used markers to improve breeding efficiency to varying degrees. Now, advances in automation technology have launched a new method in marker-assisted breeding, called “designer breeding”. Advances in applied genomics and the possibility of generating large-scale marker datasets have provided us with tools to determine the genetic basis of all important agronomic traits. Methods for evaluating allelic variation at loci of important agronomic traits are now also available, and this comprehensive knowledge will ultimately allow breeders to combine favorable alleles at all these loci in a controllable way to obtain excellent varieties.
Changing concepts and molecular methods provide opportunities for improving breeding strategies. Knowledge about the map positions and allelic variation of important agronomic trait loci, combined with available, easily assayed molecular markers, makes the design of excellent varieties possible. DNA markers have advantages such as increased reliability, improved efficiency and reduced cost, and can greatly accelerate the time required for variety development.
The use of DNA markers for indirect selection provides huge benefits for quantitative traits with low heritability, because these traits are the most difficult to evaluate in field trials. Obviously, because such traits require extensive phenotypic measurement, the development of marker-assisted analysis for such traits is difficult and expensive. However, once knowledge of the estimated parameters is available, a carefully designed experimental setup will make it possible to use marker-assisted selection tools, which can be reduced to one major scope. Molecular marker technology will help identify favorable alleles for agronomic traits, associate these alleles with specific molecular markers, and introduce them from one genetic background into another through MAS.