Model Answer
0 min readIntroduction
Mass selection is a traditional and relatively simple plant breeding technique used to improve crop yields and quality. It involves selecting plants with desirable traits from a mixed population and using their seeds for the next generation. This method is particularly valuable in self-pollinated crops like rice, wheat, and groundnut, where genetic purity is maintained through self-pollination. Historically, it was a cornerstone of crop improvement programs before the advent of more sophisticated molecular techniques. The technique’s simplicity and low cost make it still relevant in resource-constrained environments, particularly for initial varietal improvement.
What is Mass Selection?
Mass selection is a phenotypic selection method where a large number of plants (typically 500-1000 or more) are visually inspected and the best individuals are chosen based on overall performance. Seeds from these selected plants are mixed and used as the parent population for the next generation. This process is repeated over several cycles (usually 6-8 generations) to gradually improve the desired traits.
Applications in Self-Pollinated Crops
Self-pollinated crops are ideal for mass selection because self-pollination ensures that the progeny largely inherit traits from the selected parent. This minimizes the influence of undesirable genes from other plants. Here's how it's applied:
- Initial Population: Start with a diverse population of the crop.
- Selection: Farmers or breeders visually assess plants based on traits like yield, disease resistance, grain quality, or plant height.
- Seed Collection: Seeds are collected only from the selected plants.
- Replication: The process is repeated over multiple generations, with each generation representing an improved population.
- Example: In India, mass selection has been used extensively to improve rice varieties, particularly in local farmers' fields to adapt to specific agro-climatic conditions.
Merits of Mass Selection
- Simplicity & Low Cost: Requires minimal infrastructure and expertise.
- Rapid Cycle Time: Relatively quick compared to pedigree or backcross methods.
- Adaptability: Allows for adaptation to local conditions by farmers themselves.
- Broad Genetic Base: Maintains a wider genetic base compared to pure line selection, potentially increasing resilience.
- Suitable for Farmers: Farmers can easily participate in the selection process, promoting ownership and adoption.
Demerits of Mass Selection
- Limited Genetic Gain: The rate of genetic improvement is slower compared to more sophisticated techniques.
- Selection of Unadapted Recombinants: Occasionally selects plants that are not true breeding due to rare outcrossing events.
- Dependence on Phenotype: Relies solely on observable traits, potentially missing beneficial genes not easily expressed.
- Risk of Regression: The selected plants might regress towards the mean in subsequent generations if selection pressure isn’t maintained.
- Requires Large Population Size: To minimize the risk of selecting undesirable recombinants, a large initial population is needed.
Comparison Table: Mass Selection vs. Pure Line Selection
| Feature | Mass Selection | Pure Line Selection |
|---|---|---|
| Genetic Purity | Less stringent initially; gradually improves with generations | High from the start; involves selecting individual plants with known genetic background |
| Genetic Gain | Slower | Faster |
| Cost & Complexity | Lower | Higher |
| Population Size | Larger | Smaller |
The National Seeds Corporation (NSC) in India utilizes mass selection techniques, along with other breeding methods, to develop and distribute improved varieties of various crops.
Conclusion
Mass selection remains a valuable tool for crop improvement, particularly in resource-limited settings and for involving farmers in the breeding process. While it offers simplicity and adaptability, its limitations in terms of genetic gain necessitate its integration with more advanced breeding techniques. Future research should focus on combining mass selection with marker-assisted selection to enhance its efficiency and precision, maximizing its potential for sustainable agriculture and food security.
Answer Length
This is a comprehensive model answer for learning purposes and may exceed the word limit. In the exam, always adhere to the prescribed word count.