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