selfsterile

Selfsterile, or self-incompatibility, is a biological property of some organisms that prevents fertilization by self-pollen or selfing. In plants, self-sterility is a common mechanism that promotes outcrossing and genetic diversity by blocking pollen from a flower if the pollen’s genotype matches the pistil’s genotype at specific loci. In animals and fungi, analogous concepts exist where mating with genetically similar individuals is restricted, though the underlying systems differ.

In flowering plants, self-incompatibility is typically governed by a genetic locus known as the S-locus. Two main forms are recognized: sporophytic self-incompatibility (SSI), in which the parent plant’s genotype determines the pollen phenotype, and gametophytic self-incompatibility (GSI), in which the pollen’s own genotype determines compatibility. Pollen carrying an S-allele that matches any S-allele in the pistil is rejected, often by arresting pollen tube growth or degrading genetic material. The result is that self-pollination is prevented and cross-pollination with different individuals is favored. Many crops and fruit trees exhibit self-incompatibility, including apple (Malus domestica) and other members of Rosaceae and Brassicaceae families.

In fungi, self-sterility is often described in terms of heterothallism, where strains possess distinct mating types and can only mate with strains of a different type. This ensures genetic recombination through outcrossing rather than self-fertilization.

Biological and agricultural significance includes maintaining genetic diversity, influencing orchard and crop management, and guiding breeding strategies. Breeders may leverage or overcome self-sterility to achieve hybridization or stable self-compatibility, depending on the goals.