Mutation Breeding
Definition
Mutation breeding is a plant breeding method in which heritable genetic changes (mutations) are artificially induced using physical or chemical mutagens to develop new and improved plant varieties with desirable traits such as higher yield, disease resistance, early maturity, or improved quality.
History
Mutations were first scientifically explained by Hugo de Vries (1901).
The practical use of mutations in plant breeding began after the discovery of X-rays by H.J. Muller (1927).
The first mutant variety developed was ‘Chlorina’ tobacco.
FAO and IAEA have promoted mutation breeding worldwide.
Principle of Mutation Breeding
Mutagens cause changes in DNA sequences.
These changes may alter gene function or expression.
Beneficial mutations are selected and stabilized through generations.
Mutation breeding does not involve hybridization.
Types of Mutations Used
Gene (Point) Mutations – Change in a single gene
Chromosomal Mutations – Structural changes (deletions, inversions)
Genome Mutations – Change in chromosome number (polyploidy)
Mutagens Used in Mutation Breeding
1. Physical Mutagens
X-rays
Gamma rays (most commonly used)
Alpha and beta particles
UV rays
Fast neutrons
2. Chemical Mutagens
Ethyl Methane Sulphonate (EMS)
Diethyl Sulphate (DES)
Nitrous acid
Sodium azide
Mustard gas
Materials Used for Treatment
Seeds
Pollen grains
Vegetative propagules (cuttings, tubers)
Tissue culture materials
Steps in Mutation Breeding
1. Selection of Plant Material
Well-adapted and popular varieties are chosen.
2. Mutagen Treatment
Seeds or plant parts treated with physical or chemical mutagens.
Proper dose is determined using LD₅₀ (lethal dose for 50%).
3. Raising M₁ Generation
Treated material grown.
Mutations generally not visible due to heterozygosity.
4. Raising M₂ Generation
Individual plant selection.
Mutations become visible and selectable.
5. Selection and Evaluation
Desirable mutants selected for traits like yield, disease resistance.
6. Stabilization and Testing
Mutants tested over generations and locations.
7. Release of Variety
After successful trials, variety is released.
Achievements / Examples of Mutant Varieties In India
Sharbati Sonora (Wheat) – early maturity
Pusa Lerma – rust resistance
Jagannath (Rice) – semi-dwarf
Trombay groundnut varieties
Globally
Over 3,400 mutant varieties released worldwide.
Major crops: rice, wheat, barley, cotton, groundnut.
Advantages of Mutation Breeding
Creates new genetic variation
Useful in self-pollinated crops
Improves one or two traits without altering rest
Saves time compared to conventional breeding
Useful where hybridization is difficult
Maintains original variety characteristics
Limitations of Mutation Breeding
Most mutations are deleterious
Requires screening of large populations
Mutations are random
Possibility of undesirable linked traits
Needs skilled handling and facilities
Low frequency of useful mutations
Applications of Mutation Breeding
Development of disease and pest resistance
Improved quality traits (protein, oil content)
Early maturity and dwarfism
Abiotic stress tolerance (drought, salinity)
Ornamentals (flower color, shape)
Conclusion
Mutation breeding is a powerful and efficient method for crop improvement. It has contributed significantly to agricultural productivity by generating valuable genetic variability. Though it has limitations, its integration with modern techniques like tissue culture and molecular breeding has enhanced its effectiveness.
Here are MCQs on Mutation Breeding, useful for competitive exams, university tests, ICAR, JRF, NET, and semester exams.
MCQs on Mutation Breeding
1. Mutation breeding is based on
A. Hybridization
B. Polyploidy
C. Induced mutations
D. Genetic engineering
✅ Answer: C. Induced mutations
2. Who first proposed the mutation theory?
A. Mendel
B. Hugo de Vries
C. Morgan
D. Muller
✅ Answer: B. Hugo de Vries
3. The most commonly used physical mutagen in mutation breeding is
A. UV rays
B. X-rays
C. Gamma rays
D. Beta particles
✅ Answer: C. Gamma rays
4. Which of the following is a chemical mutagen?
A. X-rays
B. Gamma rays
C. EMS
D. Fast neutrons
✅ Answer: C. EMS
5. LD₅₀ refers to
A. Lethal dose for 100% plants
B. Dose causing 50% mutation
C. Dose killing 50% of treated population
D. Dose giving maximum yield
✅ Answer: C. Dose killing 50% of treated population
6. Mutations are first effectively selected in
A. M₁ generation
B. M₂ generation
C. M₃ generation
D. M₀ generation
✅ Answer: B. M₂ generation
7. Mutation breeding is most suitable for
A. Cross-pollinated crops
B. Self-pollinated crops
C. Vegetatively propagated crops only
D. Forest trees
✅ Answer: B. Self-pollinated crops
8. Which mutagen causes point mutations most frequently?
A. Gamma rays
B. Fast neutrons
C. EMS
D. X-rays
✅ Answer: C. EMS
9. Which crop has the highest number of mutant varieties released worldwide?
A. Wheat
B. Rice
C. Maize
D. Barley
✅ Answer: B. Rice
10. The first mutant variety released in India was
A. Sharbati Sonora
B. Jagannath
C. Trombay Groundnut
D. Pusa Lerma
✅ Answer: A. Sharbati Sonora
11. Fast neutrons mainly induce
A. Point mutations
B. Chromosomal deletions
C. Polyploidy
D. Gene duplication
✅ Answer: B. Chromosomal deletions
12. Mutation breeding does NOT involve
A. Selection
B. Mutagens
C. Hybridization
D. Screening
✅ Answer: C. Hybridization
13. Which organization promotes mutation breeding globally?
A. CGIAR
B. FAO–IAEA
C. WHO
D. IRRI
✅ Answer: B. FAO–IAEA
14. Sodium azide is classified as
A. Physical mutagen
B. Biological mutagen
C. Chemical mutagen
D. Radiological agent
✅ Answer: C. Chemical mutagen
15. A major limitation of mutation breeding is
A. Lack of variation
B. High frequency of useful mutations
C. Random nature of mutations
D. Long breeding cycle
✅ Answer: C. Random nature of mutations
16. Mutation breeding is especially useful for improving
A. Complex quantitative traits
B. Single gene traits
C. Cytoplasmic traits
D. Polygenic traits only
✅ Answer: B. Single gene traits
17. Chlorophyll mutations are commonly observed in
A. M₁ generation
B. M₂ generation
C. M₃ generation
D. M₄ generation
✅ Answer: B. M₂ generation
18. Which generation is used for stability testing of mutants?
A. M₁
B. M₂
C. M₃ onwards
D. M₀
✅ Answer: C. M₃ onwards
19. Mutation breeding is widely used in ornamentals to improve
A. Yield
B. Root depth
C. Flower colour and shape
D. Nitrogen fixation
✅ Answer: C. Flower colour and shape
20. EMS primarily causes
A. Deletions
B. Insertions
C. Base substitutions
D. Chromosome doubling
✅ Answer: C. Base substitutions
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