selfcompatible

Self-compatible, or self-compatibility, is a trait in flowering plants that enables fertilization from the plant’s own pollen, allowing self-pollination and seed production without the need for cross-pollination from other individuals. It is commonly discussed in contrast to self-incompatibility, a genetic mechanism that prevents self-fertilization to encourage outcrossing and genetic diversity.

In many species, self-incompatibility is controlled by a genetic region known as the S-locus, which includes pistil and pollen proteins that recognize and reject self-pollen. In self-compatible species, this recognition system is effectively broken or bypassed. Mechanisms include loss-of-function mutations at S-alleles, changes in the expression or function of SI components, or alternative pathways that permit pollen tube growth and fertilization despite self-pollen. Some plants also employ structural traits that promote selfing, such as cleistogamy, where flowers mature and fertilize before opening.

Self-compatibility has important ecological and evolutionary consequences. It provides reproductive assurance in environments with few pollinators or in small, isolated populations, enabling seed production when cross-pollination is unlikely. However, increased selfing can raise the incidence of inbreeding and reduce genetic diversity, potentially affecting adaptation and long-term fitness. Many plant lineages balance selfing and outcrossing through mixed mating systems, with varying rates across individuals or populations.

In agriculture and horticulture, self-compatibility is often advantageous for seed production and breeding. It allows the rapid development of inbred lines and reliable seed sets, facilitating hybrid development and commercial propagation in crops such as tomato and several cereals and legumes. Model species like Arabidopsis thaliana have been instrumental in studying the genetics and evolution of self-compatibility.