Explain how mass selection will be of help in a successful breeding program. Elaborate the answer with a suitable example.

Understanding Mass Selection

Mass selection is a method of crop improvement where superior plants are chosen from a mixed population based on their overall phenotype (observable characteristics). The seeds collected from these selected plants are then bulked together and used to grow the next generation. This process is repeated over several generations, gradually improving the desired traits in the population. It’s particularly effective when the desired trait is governed by polygenes – multiple genes with small, additive effects.

Steps Involved in Mass Selection

1. Population Establishment: Begin with a diverse population of the crop species.
2. Phenotypic Observation: Carefully observe and evaluate individual plants within the population for the desired traits (e.g., yield, disease resistance, grain quality).
3. Selection of Superior Plants: Identify and select plants exhibiting the most desirable combination of traits. The number of selected plants depends on the population size and the heritability of the traits.
4. Seed Collection and Bulking: Collect seeds from the selected plants and mix them together to create a composite seed sample.
5. Repetition: Repeat the process of observation, selection, and seed collection for multiple generations (typically 5-10) to achieve significant improvement.

Advantages of Mass Selection

• Simplicity: It is a relatively simple and inexpensive method, requiring minimal equipment and expertise.
• Effectiveness in Self-Pollinated Crops: Highly effective in self-pollinated crops where genetic recombination is limited, preserving the desirable traits.
• Broad Genetic Base: Maintains a broader genetic base compared to other methods like pedigree selection, reducing the risk of inbreeding depression.
• Adaptability: Can be easily adapted to local conditions and farmer preferences.

Limitations of Mass Selection

• Environmental Influence: Phenotypic expression can be influenced by environmental factors, leading to inaccurate selection.
• Lack of Controlled Crossing: Does not involve controlled crossing, so the genetic gains per generation are relatively slow.
• Difficulty in Selecting for Multiple Traits: Selecting for multiple traits simultaneously can be challenging, as some traits may be negatively correlated.
• Ineffective in Cross-Pollinated Crops: Less effective in cross-pollinated crops due to high levels of genetic recombination.

Example: Improving Wheat Yield in India

Historically, mass selection played a vital role in improving wheat varieties in India. In the early 20th century, Indian wheat yields were low due to the presence of numerous local landraces with varying characteristics. Researchers at the Indian Agricultural Research Institute (IARI) initiated mass selection programs using locally adapted wheat varieties. They selected plants with high grain yield, bold seeds, and resistance to common wheat diseases like rust. Over several generations of mass selection, they developed improved wheat varieties like ‘NP 204’ (released in 1963) which contributed significantly to the Green Revolution in India. NP 204, though later superseded by high-yielding semi-dwarf varieties, demonstrated the power of mass selection in enhancing yield potential. The process involved repeatedly selecting the best-performing plants from large populations and using their seeds for subsequent generations. This resulted in a gradual increase in average grain yield and improved adaptation to Indian growing conditions.

Mass Selection vs. Other Breeding Methods

Feature	Mass Selection	Pedigree Selection	Pure Line Selection
Crossing	No controlled crossing	Controlled crossing followed by selection	Selection from homozygous lines
Genetic Recombination	Limited	High	None
Effectiveness	Self-pollinated crops	Both self & cross-pollinated	Self-pollinated crops
Complexity	Simple	Complex	Moderate