It is the inability of a plant producing functional female and male gametes to self-seed when self-pollinated.
It is met with both in heteromorhphic species with differences in morphology of flowers of different plants and in homomorphic species with no differences in floral morphology.
The term “Self incompatibility” was originally coined by Stout in 1917
Incompatibility is due to some physiological hindrance to fertilization caused by the failure of pollen to germinate on the stigma or slow growth of the pollen tube along the style sometimes fertilization is effected, but the embryo degenerates at a very early stage.
The main features of self-incompatibility are;
- It is an important out breeding mechanism, which prevents autogamy and promotes allogamy.
- Self-incompatible species do not produce seed on self-pollination but lead to normal seed set on cross-pollination.
- It maintains high degree of heterozygosity in a species due to out breeding and reduces homozygosity due to elimination of in breeding of selfing.
- Self-incompatibility results due to morphological genetic, physiological and biochemical causes. It is not under single genetic control.
- Self-incompatibility reaction can operate at any stage between pollination and fertilization.
- Self-incompatibility has been reported in about 70 families of angiosperms including several crop species