Principles of Plant Breeding (2+1)

Comparison of dominance and over dominance hypothesis

Feature	Hypothesis of heterosis
	Dominance	Over dominance
Similarities
Inbreeding leads to	Reduced vigour and fertility	Reduced vigour and fertility
Out crossing leads to	Heterosis	Heterosis
Degree of heterosis increases with	Genetic diversity in parents	Genetic diversity in parents
Differences
Inbreeding depression is the result of	Homozygosis for deleterious recessive alleles	Homozygosity itself
Heterosis is the result of	Masking of the harmful effects of recessive alleles by their dominant alleles	Heterozygosity itself
The phenotype of heterozygote is	Comparable to that of the dominant alleles	Superior to both the homozygotes
Inbreds as vigorous as the F1 hybrids	Can be isolated	Cannot be isolated