Self-Incompatibility – Definition & Detailed Explanation – Botanical Terms Glossary

What is Self-Incompatibility?

Self-incompatibility is a genetic mechanism found in certain plant species that prevents self-fertilization. In other words, plants with self-incompatibility are unable to produce viable seeds when pollen from the same plant is used for fertilization. This mechanism promotes outcrossing, which increases genetic diversity within a population.

How does Self-Incompatibility work in plants?

Self-incompatibility in plants is controlled by a genetic system known as the S-locus. The S-locus contains two types of genes, S-alleles and S-genes, that determine whether self-pollination will be successful. When pollen is transferred from the anther to the stigma of a plant, the S-genes on the pollen interact with the S-alleles on the stigma. If the S-alleles of the pollen and stigma are compatible, fertilization can occur. However, if they are incompatible, the pollen tube will be inhibited from reaching the ovule, preventing fertilization.

What are the different types of Self-Incompatibility mechanisms?

There are two main types of self-incompatibility mechanisms in plants: gametophytic self-incompatibility (GSI) and sporophytic self-incompatibility (SSI). In GSI, the compatibility of pollen and stigma is determined by the genotype of the pollen grain itself. In SSI, the compatibility is determined by the genotype of the parent plant that produced the pollen. Additionally, there are different genetic systems that control self-incompatibility, such as the S-RNase system in Rosaceae plants and the S-gene system in Solanaceae plants.

What are the advantages of Self-Incompatibility in plants?

Self-incompatibility provides several advantages to plants. By promoting outcrossing, self-incompatibility increases genetic diversity within a population, which can enhance the adaptability of a species to changing environmental conditions. It also reduces the likelihood of inbreeding depression, which can result in decreased fitness and reproductive success. Additionally, self-incompatibility can prevent the spread of deleterious mutations within a population.

How do plants overcome Self-Incompatibility barriers?

Plants have evolved various mechanisms to overcome self-incompatibility barriers. One common mechanism is the production of multiple S-alleles within a population. This ensures that there is a higher likelihood of compatibility between pollen and stigma. Some plants also have mechanisms to prevent self-pollen from reaching the stigma, such as physical barriers or temporal separation of male and female reproductive structures. Additionally, some plants can bypass self-incompatibility by producing apomictic seeds, which are produced without fertilization.

What are some examples of plants that exhibit Self-Incompatibility?

Many plant species exhibit self-incompatibility, including members of the Rosaceae, Solanaceae, and Brassicaceae families. Some well-known examples of plants with self-incompatibility include apple trees (Malus domestica), cherry trees (Prunus avium), tomato plants (Solanum lycopersicum), and cabbage plants (Brassica oleracea). These plants have evolved different self-incompatibility mechanisms to ensure successful outcrossing and maintain genetic diversity within their populations.