Advantages of Using Markers in Breeding

  • They can save a lot of time in the breeding process
  • They may aid in discovering more information about the function of the gene of interest
  • They have many uses, including genetic diversity assessment, quality control (e.g. in variety development), marker-assisted breeding (the focus of this module) and others

(Peleman and van der Voort 2003)

Let’s look at a few of the advantages in more detail, as well as some disadvantages

Advantages of MAB: Time

  • When a marker is genetically linked to a trait, its use can speed up the identification of genetically superior plants.
  • DNA can be extracted from very young plants and the marker assay carried out long before the  plant expresses the actual trait. 
person places some plant tissue in a centrifuge tube.
  • DNA can be extracted from plants at a very early stage, much sooner than most traits can be seen or measured.  This person is harvesting leaves for DNA extraction from tomato seedlings just a few days after germination. 
  • As most characteristics of a plant cannot be visually seen or measured until the plant is older (fruit size, height, grain yield, etc.) this can save months (or years). 
  • A typical breeding programme involves a number of consecutive generations, so time savings can add up to years, especially where a generation time is long - such as in tree crops!

Maritime Pine (free image from Wikipedia)

Depending on the trait, the use of MAB can also reduce costs. Maintaining  field plots and greenhouse space, and employing labour to measure traits can be expensive, and sometimes (for example certain diseases), impossible. The ability to test for the presence of a certain allele when the plant is still small rather than waiting until the associated trait can be seen can decrease the amount of phenotyping that is necessary.

Image: TM Fulton

Products such as the FTA cards (http://www.whatman.com) shown at left can make DNA extractions, and therefore marker work, easier. This person is extracting DNA using a very simple procedure and a very young plant.

Of course, some phenotyping will always be required to confirm results, but MAB can decrease the amount of phenotyping in many situations.  

Advantage of MAB: Not subject to environmental effects

  • Because they are not subject to environmental effects, markers ensure that a trait can be selected regardless of the conditions (location and climate) where the plants are grown. Furthermore, new varieties developed can be identified and tracked with their unique genetic fingerprint.

An example of a genetic fingerprint using AFLP markers. Image from Keygene

  • Using markers can also give us a deeper understanding of the traits we are selecting for and HOW they work. This could allow for more efficient selection in the future.
    • For example, once a marker – trait correlation is established, the marker can be used to clone the gene, and more thoroughly study its action. In tomato, a major QTL affecting fruit weight was cloned and found to control carpel cell number early in fruit development (Frary et al. 2000).
large tomato next to a small tomato