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- In case of self-pollinated crops, mass selection has two major applications:
- Improvement of desi or local varieties, and
- Purification of the existing pureline varieties
- Mass selection is useful for the improvement of land, desi or local varieties of self-pollinated crops.
- The local varieties are mixtures of several genotypes, which may differ in flowering or maturity time, disease resistance, plant height, etc.
- Many of these plant types would be inferior and low yielding.
- As a result, they would lower the performance of the local variety.
- Hence the elimination of poor plant types through mass selection would improve the performance and uniformity of the variety.
- The local varieties have been under cultivation for a long time.
- Therefore, they would generally be well adapted to the local environment and would be relatively stable in their performance.
- Mass selection would improve the local variety without adversely affecting its adaptability and stability because the new variety would be made up of most of the superior plant types present in the original local variety.
- Purelines tend to become variable with time due to mechanical mixtures, natural hybridization and mutation.
- It is, therefore, necessary that the purity of pureline varieties be maintained through regular mass selection.
- At present, mass selection is used precisely for this purpose, and the nucleus seed of pureline varieties is produced through mass selection.
- Thus as a breeding method, mass selection has only a limited application for the improvement of self-pollinated crops.
- It is generally not used for the handling of segregating populations derived from hybridization.
- But it has been used for the selection of desirable traits in segregating populations, e.g., for seed size in oats.
- But this application is of limited scope where mass selection for the concerned character is rather easy and avoids extensive data collection necessary for single plant selection, e.g., for days to maturity, seed size, etc.
- However, in breeding of cross-pollinated species, mass selection has been very important.
- In such crops, inbreeding must be avoided since it leads to a loss in vigour and yield.
- In case of mass selection, several plants are selected and their seeds are bulked together to raise the next generation; therefore, inbreeding is avoided or kept to a minimum.
- Further, because of the heterozygous nature of the population, several cycles of mass selection may effectively be practised
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