Line Breeding: Merits and Demerits | Plant Breeding | Botany

In this article we will discuss about the meaning, merits and demerits of line breeding.

Meaning of Line Breeding:

A system of breeding in which a number of genotypes with superior performance for several characters are composited to form a variety is known as line breeding. A breeding method of cross pollinated species in which many genotypes with superior performance for several characters are mixed together to form a variety is called line breeding.

Main points related to line breeding are given below:

1. Application:

Line breeding approach is commonly used in animal breeding and less frequently in plant breeding. In plant breeding it is used mostly in cross pollinated species.

2. Approach:

Line breeding can involve crossing between closely or distantly related lines, but it does not emphasize continuous inbreeding.

3. Purpose:

The main purpose of line breeding is to transmit a large proportion of desirable genes from generation to generation without causing an increase in the frequency of undesirable traits often associated with inbreeding.

4. Genetic Constitution:

In cross pollinated species, a variety developed by line breeding approach consists of several homo and heterozygotes and thus has genetic diversity.

5. Adaptation:

A variety developed by line breeding approach has wider adaptation due to presence of genetic diversity.

6. Reconstitution:

Reconstitution of a variety developed by line breeding approach is not possible due to change in the gene frequencies.

7. Maintenance:

A variety developed by line breeding approach is maintained by open pollination which permits pollination by both superior and inferior pollen plants.

Merits and Demerits of Line Breeding:

Intensive inbreeding (and resulting increased homozygosity) is often directly related to an increase in the expression of many undesirable traits. Line breeding is usually associated with little risk of producing undesirable individuals. Line breeding does not necessarily cause a rapid increase in homozygous gene pairs.

Consequently, it will not expose undesirable recessive genes as extensively as inbreeding. For this reason, line breeding is generally a safer program for improvement of cross pollinated species.

The main demerit of this approach is that there is no control over the pollination. The pollination is effected by both superior and inferior pollen producing plants.