Theories of heterosis

Theories of heterosis
  • The term heterosis was first used by Shull in 1914.
  • Heterosis is often called true heterosis or euheterosis.
  • Heterosis may be defined as the superiority of an F1 hybrid over either its parents in terms of yield or some other character.
  • Heterosis or euheterosis is classified as mutational and balanced heterosis.
  • Mutational heterosis results from dominance gene action, i.e., masking of the deleterious effects of recessive mutant alleles by their dominant counterparts.
  • Balanced heterosis, on the other hand, arises due to over-domianace gene action, i.e. superiority of the heterogygote over both the corresponding homozygotes.
Causes – Basis of Heterosis
  • Various basis or causes of heterosis can be listed as follows
  • Genetic basis
  • Dominance hypothesis
  • Overdominance hypothesis
  • Epistasis
  • Physiological basis
  • Cytoplasmic basis
  • Biochemical basis

Last modified: Monday, 2 April 2012, 4:37 PM