Читать книгу Principles of Plant Genetics and Breeding - George Acquaah - Страница 202

Genomic selection and its application in plant breeding is the subject of Chapter 25. Selection in conventional plant breeding generally relies on breeding values estimated from pedigree‐based mixed models that cannot account for Mendelian segregation, and in the absence of inbreeding, can only explain one half of the genetic variability (individual contributes only half of its alleles to the next generation as previously stated). Molecular markers have the capacity to track mendelian segregation as several positions of the genome of the organism, thereby increasing the accuracy of estimates of genetic values (and the genetic progress achievable when the predictions are used for selection in breeding). Even though marker‐assisted selection (MAS) (see Chapter 24) has achieved some success, its application to improving quantitative traits is hampered by various factors. The biparental mating designs used for detection of loci affecting quantitative traits and statistical methods used are not well‐suited to traits that are under polygenic control (MAS uses molecular markers in linkage disequilibrium with QTL).

Genomic selection (or genome‐wide selection) is proposed as a more effective approach to improving quantitative traits. It uses all the available molecular markers across the entire genome (there are thousands of genome‐wide molecular markers) to estimate genetic or breeding values. Using high‐density marker scores in the prediction model and high throughput genotyping, genomic selection avoids biased marker effect estimates and captures more of the variation due to the small‐effect QTL. Genomic selection has advantages. It can accelerate the selection cycles and increase the selection gains per unit time.