Principles of Plant Breeding (2+1)

Inbreeding

• It is mating between individuals related by descent or having common ancestry. The highest degree of inbreeding is obtained by selfing. Inbreeding depression refers to decrease in fitness and vigour due to inbreeding. The degree of inbreeding is measured by the inbreeding coefficient.

History of inbreeding:
In breeding depression has been recognised by man for a long time. Knowing the consequences of inbreeding many societies have prohibited marriages between closely related individuals. Darwin in 1876 published a book “cross and self fertilization in vegetable kingdom” in which he concluded that progenies obtained from self fertilization were weaker in maize. Detailed and precise information on inbreeding in maize was published by East in 1908 and Shull in 1909.

Effects of inbreeding
1. Appearance of lethal and sub lethal.
2. Reduction in vigour: Appearance of dwarf plants.
3. Reduction in reproductive ability - Less seed set, sterility.
4. Segregation of population in distinct lines.
5. Increase in homozygosity.
6. Reduction in yield.