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Current Category » Principles of Plant Breeding

Effects of Inbreeding

Inbreeding is due to a reduction in vigour and reproductive capacity that is fertility. There is a general reduction in the size of various plant parts and in yield. The effects of inbreeding may be summarised as under.

a) Appearance of Lethal and Sublethal Alleles:

Inbreeding to the appearance of lethal, sublethal and subvital characteristics. Such characteristics include chlorophyll deficiencies E.g Albino, chlorine rootles seedlings , defects in flower structure etc. generally, plants carrying such characteristics cannot maintained and are lost from the population.

b) Reduction in Vigour:

There is a general reduction in the vigour of the population. Plants become shorter and weaker because of general reduction in the size of various plant parts.

c) Reduction in Reproductive Ability:

The reproductive ability of the population decreases rapidly. Many lines (plant progenies) reproduction poorly that they cannot be maintained.

d) Separation of the Population into Distinct Lines:

The population rapidly separates into phenotypically distinct lines. This is because of an increase in homozygosity due to which there is random fixation of various alleles of different lines. Therefore, the lines differ in their genotype and consequently in phenotype.

e) Increase in Homozygosity:

Each line becomes increasingly homozygous following inbreeding. Consequently, the variation within a line decreases rapidly. Ultimately, after 7 to 8 generations of selfing, the lines become almost uniform. Since they approach complete homozygosity (> 99 percent homozygosity). The lines, which are almost homozygous due to continued inbreeding and are maintained through close inbreeding, are known as inbred lines or inbreds.

i) Reduction in Yield:

Inbreeding generally leads to a loss in yield. The inbred lines that is able to survive and be maintained yield much less than the open pollinated varieties from which they were derived. In maize, the best – inbred lines yield about half as much as the open pollinated varieties from which they were produced. In alfalfa and carrot, the reduction in yields is much greater, while in onions and many cucurbits the reduction in yield is very small.

Current Category » Principles of Plant Breeding