Marker-assisted selection is the general direction of future breeding

Conventional breeding methods have limitations such as genetic variation and genomic hybridization. In principle, these limitations can be overcome by genetic engineering methods such as recombinant DNA. Using these methods, genes with definite function can be cloned and introduced into different species in a rapid and highly specialized way. As a result, a variety of organisms have become useful sources of alleles, avoiding the mixing of the entire genome. At present, the basic limitation of the application of genetic engineering seems to be the public acceptance of genetically modified organisms obtained by gene cloning and transformation.

Conventional breeding methods have limitations such as genetic variation and genomic hybridization.

In marker-assisted selection (MAS) breeding, plant breeders take advantage of the association between agronomic traits and allelic variations in genetic markers (mainly molecular markers). The general idea of marker-assisted breeding is that before breeders can make use of the linkage-based association between traits and markers, the association must be evaluated with a certain degree of accuracy. thus marker genotypes can be used as indicators or predictors of genotypes and phenotypes of traits. Once the marker trait association has been reliably evaluated, breeders can monitor the transmission of trait genes through closely linked markers, so they can carry out "genotype construction", that is, through carefully planned hybridization and selection, marker genotypes are used as selection criteria to construct the desired genotypes.

The potential value of genetic markers, linkage maps and indirect selection in plant breeding has been recognized for more than 80 years. Since the emergence of DNA marker technology in the 1980s it has significantly improved the efficiency of plant breeding. In the past 20 years, many breeding companies have used markers to improve the efficiency of breeding to varying degrees. Now, advances in automation technology have launched a new method in marker-assisted breeding, called "design breeding". Advances in applied genomics and the possibility of generating large-scale marker data sets provide us with tools to determine the genetic basis of all important agronomic traits. Now there are methods to evaluate the allele variation of important agronomic trait loci, and this comprehensive knowledge will eventually allow breeders to combine all the favorable alleles at these loci in a controllable way to get good varieties.

Changing concepts and molecular methods provide an opportunity to improve breeding strategies. The map location and allele variation of important agronomic trait loci are only combined with available and easy-to-determine molecular markers, which makes the design of excellent varieties possible. DNA markers have the advantages of increasing reliability, improving efficiency and reducing cost, and can greatly accelerate the time of variety breeding.

The use of DNA markers in indirect selection provides great benefits for quantitative traits with low heritability because these traits are the most difficult to evaluate in field trials. Obviously, because this trait requires extensive phenotypic determination, the development of marker-assisted analysis of this trait is difficult and expensive. However, once the knowledge of parameter estimation is available, the well-designed experimental device will make it possible to use the marker-assisted selection tool, which can be reduced to a major range. Molecular marker technology will help to identify favorable alleles of agronomic traits, associate these alleles with specific molecular markers, and introduce them from one genetic background to another by MAS.