Marker Assisted Selection - Demerits of Morphological Markers

Demerits of Morphological Markers

Morphological markers are associated with several general deficits that reduce their usefulness including:

• the delay of marker expression until late into the development of the organism
• dominance
• deleterious effects
• pleiotropy
• confounding effects of genes unrelated to the gene or trait of interest but which also affect the morphological marker (epistasis)
• rare polymorphism
• frequent confounding effects of environmental factors which affect the morphological characteristics of the organism

To avoid problems specific to morphological markers, the DNA-based markers have been developed. They are highly polymorphic, simple inheritance (often codomimant), abundantly occur throughout the genome, easy and fast to detect, minimum pleiotropic effect and detection is not dependent on the developmental stage of the organism. Numerous markers have been mapped to different chromosomes in several crops including rice, wheat, maize, soybean and several others. Those markers have been used in diversity analysis, parentage detection, DNA fingerprinting, and prediction of hybrid performance. Molecular markers are useful in indirect selection processes, enabling manual selection of individuals for further propagation.