Occurrence of Heterosis in cross and self-pollinated crops:
Among the cultivated crop plants Heterosis has been frequently reported in maize, bajra, sorghum, brinjal, onion, tobacco, barley, wheat, castor, rice, cotton, sunflower, grasses, sugar beet, legumes etc.
This phenomenon is commercially utilized in crops like onion, bajra, sorghum, tomato, sugar beet etc.
Estimation of Heterosis: There are three different ways of estimating heterosis-
(1) Average or Relative heterosis
(2) Heterobeltiosis
(3) Useful or standard or Economic heterosis
Fixation of Heterosis:
It can be defined as the mechanism to ensure the heterotic gene combinations produced in heterotic hybrids remain intact in subsequent generation constitutes is called fixation of heterosis.
There are four principal ways of fixation of heterosis:
a. Vegetative propagation
b. Apomixis
c. Balanced lethal system
d. Polyploidy