Types of heterosis

Types of heterosis on the basis of two different criteria are given below

On the basis of origin and nature

  • Euheterosis or true heterosis
    • Mutational heterosis
    • Balanced heterosis
  • Pseudoheterosis or luxuriance

On the basis of types of estimation

  • Average or Relative heterosis
  • Heterobeltiosis
  • Useful or standard or Economic heterosis

Mutational Heterosis

It is simplest type of heterosis.

Lethal (mostly), recessive, adaptively unfavorable mutants are either eliminated or sheltered by their non-lethal, dominant and adaptively superior alleles in cross pollinated crops. This is termed as mutational heterosis.

Naturally occurring mutants are generally of recessive and less adaptive to environmental conditions, hence risk of their elimination by natural selection process is higher. Its mutational heterosis which gives them to chance to be in population by sheltering them.

Balanced Heterosis

Well balanced gene combinations which are more adaptive to environmental conditions and useful from the agriculture point of view result in balanced heterosis.

It has application in hybrid production.

Pseudoheterosis

Also termed as luxuriance. Progeny possess superiority over parents is in vegetative growth, but not in yield and adaptation, usually sterile or poorly fertile. This concept cannot be utilized in hybrid varieties production.

Average or Relative Heterosis

When heterosis is estimated over mid parental value i.e. average of two parents it is referred as average or relative heterosis.

Formula

Average heterosis = [(F1 – MP) / MP] x 100
Where, F1 = value of F1, MP = mean value of two parents

Heterobeltiosis

When heterosis is estimated over better parent it is called as heterobeltiosis.

Formula

Heterobeltiosis = [F1 – BP] / BP x 100
Where, F1 = value of F1, BP = value of better parent

Standard Heterosis

When heterosis is estimated over standard commercial hybrid it is called as standard heterosis. It has practical importance in plant breeding. It is also referred as useful or economic heterosis.

Formula

Standard Heterosis = [(F1 – SH) / SH] x 100.