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
Dominance hypothesis
The dominance hypothesis was proposed by Charles Davenport (1908). Most widely accepted hypothesis among the other explanations for heterosis.
As per this hypothesis, heterosis results due to superiority of dominant alleles over the deleterious recessive alleles by masking their effect and heterosis is in direct proportion with number of dominant genes contributed by each the parent.
Overdominance hypothesis
The overdominance hypothesis was independently developed by Edward M. East (1908) and George Shull (1908).
As per this hypothesis, heterosis results due to superiority of heterozygote over its both homozygous parents, due to complementation between divergent alleles. Here, heterosis is in proportion with heterozygosis.