SelfCompatibility

Self-compatibility is the ability of an organism to fertilize itself or to be fertilized by its own pollen or gametes. In plants, it refers to the capacity of pollen to germinate on the stigma and effect fertilization without requiring pollen from a different individual. It is the opposite of self-incompatibility, which prevents self-fertilization.

In many flowering plants, self-incompatibility is controlled by a genetic recognition system at the S-locus. Self-compatibility arises when these recognition pathways are broken by mutations in SI genes (for example SRK and SCR/SP11 in Brassicaceae) or by other modifiers, or through polyploidization or reduced expression, allowing self-pollen to germinate and fertilize ovules. Some species are self-compatible by default or have been bred to be so for agricultural purposes.

Evolutionarily, self-compatibility enables autonomous reproduction and can facilitate colonization and seed set when pollinators are scarce, but it often reduces genetic diversity and can lead to inbreeding depression. Many crop species are self-compatible, which aids unified offspring and reliable seed production, whereas wild relatives may rely on outcrossing to maintain variation. Selfing rates can vary across populations and environments.

Examples include Arabidopsis thaliana, a model plant that is self-compatible due to nonfunctional SI genes; and several cultivated crops such as wheat, rice, and tomato, which commonly exhibit self-compatibility. See also self-incompatibility and outcrossing.