Explain the following methods of plant breeding for crop improvement.

Explanation

(a) Introduction of new varieties in plants:
The process of introducing high yielding varieties of plants from one place to another is called exotic species. These imported plants may carry pathogens and pests. It should be thoroughly checked before introducing to the fields, eg. Phaseolus mungo was introduced from China.
(b) Selection: Selection is a type of plant breeding, in which individual plants or group of plants are sorted out from a mixed population based on the morphological characters.
Methods of selection:
(1) Mass selection: Seeds of plants with desired characters are collected from a mixed population. The collected seeds are allowed to raise the second generation. This process is carried out for seven or eight generations. At the end, they are distributed to the farmers for cultivation, eg. TMV-2 and AK10 (ground nut varieties)
(ii) Pure line selection:
Pureline is the progeny of a single individual obtained by self breeding". This is also called as individual plant selection. In pure line selection large numbers of plants are selected from a self-pollinated crop and harvested individually. Progeny is similar, both genotypically and phenotypically.
(iii) Clonal selection:
A group of plants produced from a single plant through vegetative or asexual reproduction are called clones. All the plants of a clone are similar both in genotype and phenotype. Selection of desirable clois from the mixed population of vegetatively propagated crop is called clonal selection