Breeding and Seed Production of Ornamental Crops (2+1)

Introduction to Mass Selection

Mass Selection

Mass selection: In mass selection a large number of plants of different desirable phenotypes are selected and their seeds are mixed together to constitute a new variety. The plants are selected on the basis of their appearance or phenotype. The population obtained from the selected plants would be more uniform than the original population.
Applications of mass selection:

1. Improvement of local varieties.
2. Purification of existing pure line varieties.

• 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. Since in mass selection several plants are selected and their seeds are mixed together to raise the next generation, 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 practiced.
• In mass selection, the inferior plants are roughed out before beginning of flowering. Some marker genes are identified at juvenile stage. For example pigmentation in leaves and stem of Antirrhinum has been commercially used to select plants. Gene markers have also been identified in Coleus and Dahlia at seedling stage for selecting a particular variety.
Procedure:
• First year: A large number of phenotypically similar plants are selected for their vigrous plant type, resistance and other desirable characters. The seeds from the selected plants are composited to raise the next generation.
• 2nd year: The composite seed is planted in a preliminary yield trial along with standard variety as checks. The variety from which selection was made should also be included as a check to determine if there has been an improvement due to selection. Phenotypic characteristics of the variety are critically observed.
• 3rd to 6th year: The variety is evaluated in coordinated yield trials at several locations. This is done to test the performance of the new variety at different locations within an agro climatic zone. If promising, the variety will be identified for release.
• 7th year: The variety may be released for cultivar if found suitable and recommended by the central on state variety release committee.
Merits of Mass selection:-

1. Since a large number of plants are selected the adoption of the original variety is not changed. It is generally accepted that a mix of closely related pure lines is more stable in performance over different environment than a single pure line. Thus varieties developed through mass selection are more widely adapted than pure lines.
2. Often extensive and prolonged yield trials are not necessary. This reduces the time and cost needed for developing a new variety.
3. It is a less demanding method. The breeder can devote more time to other breeding programmes.

Demerits:

1. The varieties developed through mass selection show variation and are not as uniform as pure line varieties.
2. The improvement through mass selection is generally less than they through pure line selection.
3. In the absence of progeny test, it is not possible to determine if the selected plants are homozygous.
4. Due to popularity of pure line varieties, mass selection is not commonly used in improvement of self palliated crops. But it is quick and convenient method of improving old local variety in the areas or crop spp where crop improvement has just begun.
5. Varieties developed by mass selection are more difficult to identify than pure line in seed certification programme.