Method of Plant Breeding in Self Pollinated Plants – Selection
One of the oldest method of breeding and is the basis for all crop improvement, practised by farmer in ancient times. Selection is essentially based on the phenotype of plants. Consequently the effectiveness of selection primarily depends upon the degree to which the phenotypes of plants reflect their genotype.
Selection may be natural or artificial by which individual or group of plants are isolated from a mixed population. Before domestication, crop species were subjected for natural selection. Natural selection is the rule and has resulted in evolution of several local varieties of crop. After domestication man has knowingly or unknowingly practiced some selection known as the artificial selection. For a long period under domestication natural selection was perhaps the more selection is a little value and current breeding method entirely depends on artificial selection.
Selection has two basic characteristics or limitation
i) Selection is effective for heritable differences.
ii) Selection does not create variation, it only utilise the variation already present in the population. Thus the two basic requirement of selection are a) Variation must be present in the population and b) Variation must be heritable.
Two methods of selection are practised in breeding self pollinated crops
i) Pure Line Selection
ii) Mass Selection.