Breeding of Vegetable, Spice and Tuber crops (2+1)

Dominance hypothesis

• The dominance hypothesis was proposed by Charles Davenport (1908),which is the 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 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