Inbreeding – Inbreeding Depression

What is Inbreeding and Inbred? – Definition

Inbreeding is mating or crossing between two closely related i.e. genetically similar individuals.

Inbred line or Inbred – is the almost homozygous line obtained by continuous inbreeding.

What is Inbreeding Depression? – Definition

Reduction in vigour or fertility because of inbreeding is called as inbreeding depression.

It was first noted by Darwin (1876). The main reason behind inbreeding depression is segregation. In F2 segregation occurs and results in the break down of heterotic gene combinations formed in F1.

Consequences / effects of Inbreeding

  • Yield reduction
  • Vigour reduction
  • Sub-lethal, lethal alleles may appear
  • Fertility reduction
  • Homozygosity increases, heterozygosity decreases because of gene fixation.
  • Fitness reduction
  • Continuous inbreeding leads to increase of total genotypic variance between the families and decrease of it within the families. It breaks the entire population into small, phenotypically distinct, non-interbreeding groups. This produces inbreds.