What is Heterosis? – Definition?
Heterosis is superiority of F1 (offspring from cross ) in one or more characters over its better parental or mid parental value.
Another term used for heterosis is hybrid vigour. Shull (1914) used this term for the first time.
Desirable heterosis can be
- Positive – like in case of yield, quality, disease resistance
- Negative – like in case of plant height, maturity duration
General Features of Heterosis
- Wide occurrence in both plants and animals
- In plants, more frequent in cross pollinated species as compared to self pollinated.
- Superiority over parents with respect to many traits like yield, disease resistance etc.
- Confined to F1 generation only, due to segregation and recombination declines and disappears in subsequent generations.
- Mostly governed by nuclear genes, in some case by interaction between nuclear genes and cytoplasm.
- Frequency of occurrence of desirable heterosis is very low.
- Easily reproducible once identified
- Positive association with specific combining ability.
- Magnitude of heterosis is directly proportional with heterozygosity.
- Can be exploited fully as in case of hybrids, or partially as in synthetic and composite varieties.
Types of heterosis
Types of heterosis based on origin and nature and type of estimation are given on the page. Visit to get details.
Causes or Basis of Heterosis
Various Causes or Basis for Heterosis like genetic, physiological are given, click to read these.
Factors affecting Heterosis
Some of the factors affecting heterosis are listed below
- Parent genotype
- Type of pollination followed
- Genetic diversity present among parents
- Parent’s adaptability
Achievements in India by Heterosis
Some of the crop varieties developed with the use of technique of heterosis are listed below.
|Cotton||Interspecific – Varlaxmi|
|Intraspecific – H-4, H-6, H-8, H-10, PKVHY-2, PKVHY-3, PKVHY-4|
|Sorghum||CSH-1, 5, 6, 9, 10, 11|
|Maize||Deccan 103, Makka1, Ganga-2, 5, 11|
|Brinjal||Pusa kranti, Vijay|