Methods for Estimation of Heterosis
Heterosis is estimated in three different ways,
1) Mid parent heterosis
2) Better parent heterosis
3) Standard heterosis
1) Mid Parent Heterosis:
When the heterosis is estimated over the mid parent i.e. mean value or average of the two parents is known as mid parent heterosis. It is also known as average heterosis or relative heterosis and calculated by using formula.
Mid Parent Heterosis = F1- MP
———– X 100
Where F1 is mean of F1 and
MP is mean of two parent
2) Better Parent Heterosis:
When the heterosis is estimated over the better parent is known as better parent heterosis. It is also known as heterobeltiosis and calculated by using formula:
Heterobeltiosis = F1- BP
——— X 100
Where BP is mean of better parents.
The term heterobeltiosis was used by Bitzer et al (1968) to describe the improvement of heterozygote over the better parent of the cross.
3) Standard Heterosis:
It refers to the superiority of F1 over the standard commercial check variety. It is also called as economic heterosis or useful heterosis and calculated by using formula.
Standard Heterosis = F1 – Check
—————— X 100
Heterosis leads to increase in yield, reproductive ability, adaptability, disease and insect resistance, general vigour, quality etc. For most of the characters, the desirable heterosis is positive. But for some characters like earliness, height in cereals and toxic substances are negative heterosis.