What is Self-incompatibility – Definition?
Self-incompatibility is a general name for all those genetic mechanisms in flowering plants / angiosperms, which prevent selfing. It is phenomenon with which a plant with functional pollen fails to set seed when self pollinated. It is incompatibility between the pollen and the stigmas of the same plant.
General features of Self-incompatibility
- Prevents selfing and promotes outbreeding so increases the probability of new gene combinations
- Causes may be morphological, physiological, genetical or biochemical
- Normal seed set on cross pollination
- May operate at any stage between pollination and fertilization
- Reduces homozygosity
- In plants, self-incompatibility is often inherited by a single gene (S) with different alleles (e.g. S1, S2, S3 etc.) in the species population
Classification of Self-incompatibility
Self-incompatibility is classified on the basis of various criteria listed as follows
| Criteria | Types | |
|---|---|---|
| Flower morphology | Heteromorphic self incompatibility | Distyly |
| Tristyly | ||
| Homomorphic self incompatibility | Sporophytic self ncompatibility | |
| Gametophytic self incompatibility | ||
| Genes involved (number) | Monoallelic (governed by single gene) | |
| Diallelic (governed by two genes) | ||
| Polyallelic (governed by many genes) | ||
| Cytology of pollen | Binucleate (pollens with two nuclei) | |
| Trinucleate (pollens with three nuclei) | ||
| Expression site | Ovarian (expression site is ovary) | |
| Stylar (expression site is style) | ||
| Stigmatic (expression site is stigma) | ||