Principles of Plant Breeding (2+1)

Marker aided selection

Marker aided selection:

1. Selection of a genotype carrying desirable gene or gene combination via linked marker is called MAS.
2. Breeders practice MAS when an important trait, that is difficult to assess, is tightly linked to another Mendelian trait which can easily scored.
3. MAS involve scoring for the presence or absence of a desired plant phenotype indirectly based on DNA banding pattern of linked markers on gel or on autoradiogram depending on the marker system.
4. The rationale is that the banding pattern revealing parental origin of the bands in segregants at a given marker locus indicates presence or absence of a specific chromosomal segment which carries the desired allele. This increases the screening efficiency in the breeding programmes in a number of ways such as.
5. Gene introgression and elimination of linkage drag
6. Molecular markers can aid introgression and impart greater precision. With the use of isozyme marker it has been possible to introgress nematode resistance in to the cultivated tomato from one of its wild relatives.
7. It is often observed that the desirable genes such as those for disease resistance remain linked with undesirable weedy characteristic of the alien species. During gene introgression by back crossing, the linked undesirable genes are also get transferred to the recipient parent. This has been referred as linkage.