Prinnciples of Pure Line Selection

 

Pure Line Selection

 

Pure line selection is one of the oldest and most important methods of plant breeding. It is mainly used for the improvement of self-pollinated crops. In agriculture, many crop plants show natural variation in characters such as plant height, maturity, grain size, seed colour, disease resistance, and yield. A plant breeder studies this variation and selects the best plant from the available population. When the selected superior plant is self-pollinated generation after generation, its progeny becomes highly uniform and stable. This uniform and genetically similar group of plants is called a pure line.

 

The concept of pure line selection has played a major role in the development of improved crop varieties. It helped breeders convert variable local populations into uniform and high-performing varieties. The method is simple, scientific, and economical, so it has remained a fundamental topic in plant breeding courses. For undergraduate students, it is essential to understand not only the definition of pure line selection but also its principles, procedure, advantages, limitations, and practical importance in crop improvement.

Principle of Pure Line Selection

Pure line selection is based on the following principles:

a. Presence of genetic variation in the original population

The original mixed population or landrace must contain genetic variability. Without variability, there is no scope for selection.

 

b. Self-pollinated crops are highly homozygous

In self-pollinated crops, repeated selfing leads to homozygosity. Therefore, the progeny of a selected plant becomes uniform and stable.

 

c. A pure line is genetically uniform

Once a pure line is isolated, all plants within it have the same genetic makeup. They differ only because of environmental influences.

 

d. Selection is effective between pure lines, not within a pure line

Improvement is possible by selecting the best pure line from among many lines in the original population. However, further selection within one pure line is not very useful because no new heritable variation exists within it.

 

These principles show that pure line selection does not create new variation. It only isolates and uses the best genotype already present in a variable population.