Breeding Procedures of Clonal Selection
The procedure of selection used for asexually propagated crops is known as clonal selection, since the selected plants are used to produce new clones. Or
Improvement of asexually propagated crop y selecting superior clones is known as clonal selection. Superior clones can be isolated from three types of materials viz. 1) Local variety, 2) Introduced variety, and 3) Inter crossed populations.
The phenotypic value of a plant or clone is due to the effects of its genotype (G) , the environment (E) and the genotype X environment ( G X E) interaction of these only the genotypic ( G) effects are heritable and therefore stable. The environment and interaction effects are non- heritable and cannot be selected for. Therefore, selection for quantitative characters based on the observation on single plants is highly unreliable. In view of this consideration , in the earlier stage of clonal selection , when selection is based on single plant or single plots the emphasis is given on elimination of weak and undesirable plants or clones.
The Various Steps Involved in Clonal Selection:
1. First Year:
From a mixed variable population few hundred to few thousand desirable plants are selected. A rigid selection can be done for simply inherited characters with high heritability. Plants with obvious weaknesses are eliminated.
2. Second Year:
Clones from the selected plants are grown separately, without replication. This is done in view of the limited supply of propagating material for each clone and because of the large number of clones involved. The number of clones is crastically reduced, and inferior clones are eliminated. The selection is based on visual observation. Finally, fifty to one hundred clones may be selected on the basis of clonal characteristics.
3. Third Year:
A replicated preliminary yield trial is conducted by using suitable check for comparison. Few superior performing clones with desirable characteristics are selected for multi location trails.
4. Fourth to Sixth Years:
A replicated yield trail is conducted at several locations along with a suitable check. The best clone that is superior to the check in one or more characteristics is identified for release as a new variety.
5. Seventh Year:
The superior clone is multiplied and released as a new variety.