Induced mutations are artificially created changes in the DNA of an organism, caused by exposing it to physical or chemical agents called mutagens. In plants, induced mutations are used to create genetic variation and develop new, improved varieties for agriculture and horticulture.
Definition
An induced mutation is a mutation that does not occur naturally but is deliberately produced by scientists using external agents to change the genetic material of an organism.
How induced mutations are created
Induced mutations are produced using mutagenic agents, which can be of two main types:
1. Physical mutagens
These are different types of radiation that damage or alter DNA.
- X-rays and gamma rays: cause breaks in DNA strands, rearrangements, or deletions.
- Fast neutrons: lead to large-scale DNA changes, such as loss or duplication of genes.
- Ultraviolet (UV) radiation: causes the formation of thymine dimers, which distort DNA and lead to base-pairing errors during replication.
2. Chemical mutagens
These are chemicals that react with DNA molecules, changing their base sequences.
- Ethyl Methane Sulfonate (EMS): causes point mutations by changing single DNA bases.
- Methyl Methane Sulfonate (MMS): similar to EMS; modifies DNA bases.
- Sodium Azide (NaN₃): induces gene mutations, commonly used in cereals.
- Nitrous Acid (HNO₂): converts cytosine to uracil, leading to incorrect base pairing.
Process of creating induced mutations
- Selection of plant material: Seeds, pollen, or plant tissues are chosen for treatment.
- Exposure to mutagen: The material is treated with a physical or chemical mutagen for a controlled time and dose.
- Growth and recovery: Treated materials are grown into plants (the M₁ generation).
- Screening for mutations: The next generation (M₂ and later generations) is examined for desirable traits like disease resistance or improved yield.
Applications in plant breeding
- Development of high-yielding and stress-tolerant crops.
- Production of disease-resistant and early-maturing varieties.
- Creation of new flower colors and shapes in ornamentals.
- Introduction of genetic variability for breeding programs.
Examples
- ‘Sharbati Sonora’ wheat – a high-protein variety developed using gamma rays.
- ‘Pusa Ruby’ tomato – a mutant variety with improved fruit quality.
- ‘Prabhat’ mung bean – early-maturing and disease-resistant, created through induced mutation.
Summary
Induced mutations are deliberately created genetic changes caused by exposure to radiation or chemicals.
They are a powerful tool in plant breeding, helping scientists develop new varieties with desirable traits such as better yield, resistance, and adaptability.