Marker-assisted selection (MAS) is a plant breeding technique that uses DNA markers linked to traits of interest to guide the selection of desirable plants, rather than selecting based solely on visual phenotypes. MAS allows breeders to introgress traits from donor plants more efficiently by selecting plants with DNA markers correlated with the traits. The method has been used successfully in crops like rice and maize to develop varieties with improved disease resistance and grain quality. While MAS can speed breeding, it also has limitations like high costs and the need for well-trained personnel. Ongoing research continues to overcome challenges and make MAS technology more accessible to plant breeders around the world.

1. Marker-assisted selection (MAS)
Purti Soni
221/PBT/027
PLANT BIOTECHNOLOGY

2. AGENDA
I N T R O D U C T I O N
S T E P S
E X AM P L E S
AP P L I C AT I O N
AD VA N TA G E S
L I M I TAT I O N
F U T U R E P R O S P E C T

3. KARL SAX
In 1923, the first reported
association of a simply inherited
genetic marker with a
quantitative trait in plants
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4. introduction
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• Marker-assisted selection (MAS) uses morphological, biochemical, or DNA
markers as indirect selection criteria for selecting agriculturally important traits
in crop breeding.
• This process is used to improve the effectiveness or efficiency of selection for the
traits of interest in breeding programs.
• Instead of select for a trait, the breeder can select for a marker that can be detected
very easily in the selection scheme.
• The essential requirements for marker-assisted selection in a plant breeding program
are:
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5. • An efficient means of screening large populations for the molecular marker(s)
should be available. At present this means relatively easy analysis based on PCR
technology.
• The screening technique should have high reproducibility across laboratories.
• It should be economical to use and user-friendly.
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Steps in Marker Assisted Selection (MAS):
• Selection of parents
• Development of breeding population
• Isolation of DNA from each plant
• Scoring RFLPs
• Correlation with morphological traits
• Selection of parents- For the selection of parents, we have to screen germplasm and select
parents with distinct DNA. The parents that are used for MAS should be pure (homozygous). In
self-pollinated species, plants are usually homozygous. In cross-pollinated species, inbred lines are
used as parents.
• Development of breeding population- The selected parents are crossed to obtain
F1 plants. F1 plants between two pure lines or inbred lines are homogeneous (alike phenotypically)
but are heterozygous for all the RFLPs of two parents involved in the F1.

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• Isolation of DNA from each plant- The isolated DNA is digested with a specific
restriction enzyme to obtain fragments of DNA. The DNA fragments of different sizes
are separated by subjecting the digested DNA to agarose gel electrophoresis. The gel is
stained with ethidium bromide and the variation in DNA fragments can be viewed in
the ultraviolet light.
• Scoring RFLPs- The polymorphism in RFLPs between the parents and their
involvement in the recombinants in the F2 population is determined by using DNA
probes. The labeled probes are used to find out if the fragments have similarities.
• Correlation with Morphological Traits- The DNA marker (say RFLPs) are
correlated with morphological markers and the indirect selection through molecular
markers is confirmed. Once the correlation of molecular markers is established with
morphological markers, MAS can be effectively used for the genetic improvement of
various economic traits.

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Examples-
• Rice: In rice MAS has been successfully used for developing cultivars resistant to
bacterial blight and blast. For bacterial blight resistance, four genes (Xa4, Xa5,
Xa13, and Xa21) have been pyramided using STS (sequence-tagged site) markers.
• Maize: In maize, normal lines have been converted into quality protein maize
(QPM) lines through MAS using opaque 2 recessive alleles. This work has been
done at CIMMYT (international center for wheat and maize improvement,
Mexico).

11. Applications
• MAS is a very effective, efficient, and rapid method of transferring resistance to biotic and
abiotic stresses in crop plants.
• It is useful in gene pyramiding for disease and insect resistance.
• It is being used for the transfer of male sterility and photoperiod insensitivity into cultivated
genotypes from different sources.
• MAS is being used for the improvement of quality characteristics in different crops such as for
protein quality in maize, fatty acid (linolenic acid) content in soybean, and storage quality in
vegetables and fruit crops.
• MAS can be successfully used for transferring desirable transgene (such as the Bt gene) from
one cultivar to another.

12. Advantages
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• Accuracy: The accuracy of MAS, is very high because molecular markers are not
affected by environmental conditions. It is very effective even with the characters
having low heritability.
• Rapid Method: MAS is a rapid method of crop improvement. It takes 3-5 years for
developing a new cultivar against 10-15 years taken by the conventional method of
breeding.
• Non-transgenic Product: MAS leads to the development of non-transgenic cultivars
which are acceptable to everybody. In other words, it does not involve transgene.
Hence there is no question of gene silencing.
• Permits QTL Mapping: MAS permits mapping or tagging of quantitative trait loci
(QTL) which is not possible by conventional methods.
• Highly Reproducible: The MAS is based on a DNA fingerprinting technique and the
results of the DNA fingerprinting pattern are highly reliable and reproducible.

13. LIMITATIONS
• MAS is a costly method. It requires a well-equipped laboratory viz. expensive
equipment, glassware, and chemicals.
• MAS requires well-trained manpower for the handling of sophisticated equipment,
isolation of DNA molecules, and study of DNA markers.
• The detection of various linked DNA markers (AFLP, RFLP, RAPD, SSR, SNP, etc.) is
a difficult, laborious, and time-consuming task.
• MAS sometimes involves the use of radioactive isotopes in the labeling of DNA,
which may lead to serious health hazards. This is a major disadvantage of RFLP-based
markers. The PCR, markers are safe in this regard.
• It has been reported that MAS may become less efficient than phenotypic selection in
the long term.
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14. 2023
Marker-assisted selection (MAS)
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Future outlook
• The costly technology like MAS should be supported by the Consultative Group on International
Agricultural Research (CGIAR) which promotes collaborative research and training on global
bases. It will help in the rapid spread of technology (MAS) in developing countries.
• The FAO and Rockefeller Foundation may play a key role in making MAS technology available to
resource-poor countries.
• Private Industries should support MAS technology for the benefit of the common man and in the
global interest.
• To take advantage of such technology, there is a need for International collaboration among
research Institutes engaged in MAS programs.
• There is a need for a collaborative approach between public and private organizations to provide
access to MAS technology in developing countries.

15. summary
Marker-assisted selection (MAS) is a
method of selecting desirable individuals
in a breeding scheme based on
DNA molecular marker patterns instead of,
or in addition to, their trait values. When
used in appropriate situations, it is a tool
that can help plant breeders select more
efficiently for desirable crop traits.
However, MAS is not always
advantageous, so careful analysis of the
costs and benefits relative to conventional
breeding methods is necessary.
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16. References
• Introduction to plant biotechnology H.S. CHAWLA.
• https://doi.org/10.1098/rstb.2007.2170
• Ribaut & Hoisington 1998; Morris et al. 2003)

17. Thank
you