# Gene bank

A gene bank is a type of biorepository that serves to preserve the genetic information of organisms. Gene banks are often used for storing the genetic material of species that are endangered or close to extinction. They are also used for the preservation of major crop species and cultivars, in order to preserve crop diversity.
Preservation is done via the collection and storage of reproductive material from an organism. For example, seeds and cuttings may be collected from plants, spores may be collected from fungi and sperm and egg cells may be collected from animals. Aquatic organisms such as coral are preserved via the collection of fragments of coral, that are then sustained, live, in a carefully controlled aquatic environment.
The collected material is oftentimes stored at a temperature below 0 °C (32 °F). It may also be stored in cryogenic conditions using liquid nitrogen. Certain gene banks are based around the continuous cultivation of living organisms, such as certain species of plants being raised in a controlled nutrient medium, or artificially created habitats that then harbor certain species.
Gene banks are present all over the world, with differing objectives and resources. One of the largest is the Svalbard Global Seed Vault.
The database of the largest gene banks in the world can be queried via a common website, Genesys. A number of global gene banks are coordinated by the CGIAR Genebank Platform

## Types of gene bank
### Seed bank

Seed banks, also known as seed vaults. are large repositories where seeds of many different species are stored at freezing temperatures. They are used to preserve genetic diversity for the future. The storage temperature depends on how long the seeds are to be kept. Durations of 3–5 years (short term storage), 10-15 years (medium term storage) and 50+ years (long term storage) will typically have storage temperatures of 5 to 10 °C (41 to 50 °F), 0 °C (32 °F) and −18 to −20 °C (0 to −4 °F) respectively. Spores, such as those from pteridophytes can also be stored. However, storage organs, such as the tubers made by root vegetables, cannot be stored. It is also important that when seeds are stored, the moisture content of the seeds and the surrounding medium is kept low, otherwise the seeds will not be viable after long periods in freezing temperatures. The largest seed bank in the world is the Millennium Seed Bank housed at the Wellcome Trust Millennium Building (WTMB), located in the grounds of Wakehurst Place in West Sussex, near London.

### In vitro bank

In this technique, buds, protocorm and meristematic cells are preserved through particular light and temperature arrangements in a nutrient medium, which is either a gel or in liquid form. This technique is used to preserve seedless plants and plants that reproduce asexually or that require preservation as clones such as commercial cultivars.

### Cryobank

In this technique, a seed or embryo is preserved at very low temperatures. It is usually preserved in liquid nitrogen at −196 °C (−320.8 °F). By freezing the seeds or embryos at this temperature they can stay viable for at least a century. This is helpful for the conservation of species facing extinction. Cryobanks are utilized for the cryoconservation of animal genetic resources. An example of one of the world’s largest animal cryobanks is the frozen zoo made by the San Diego Zoo, in San Diego California. With animal cryobanks freezing embryos is preferred instead of the separate egg and sperm because the embryos are more resistant to the freezing process.

### Storage of pollen

Pollen is stored through a cryopreservation technique called vitrification. Vitrification in this context is based around the freezing of pollen grains without the formation of ice crystals, which would heavily damage the pollen. The pollen, which is stored in liquid nitrogen, is kept at temperatures of −180 to −196 °C (−292.0 to −320.8 °F). The National Seed Storage Lab in Fort Collins, Colorado currently uses this technique to store pollen. Pollen can also be freeze dried and stored at temperatures of 5 to −18 °C (41 to 0 °F). An important element that must be considered is the levels of moisture in the pollen. If the pollen grains have a low moisture content it helps increase the length of the pollen’s life. Low levels of moisture help the pollen freeze without creating ice or ice crystals, which helps preserve the life span of the pollen while it is being stored. Ideal levels of moisture content to be allowed in the pollen depends on the type of plant. The pollen from different plant species can be divided into two groups. One is binucleate pollen, which has a thicker exine and the second is trinucleate pollen, which has a thinner exine. Binucleate pollen has a higher lifespan when frozen at a low moisture level. Trinucleate pollen, however, has a higher lifespan when frozen at a high moisture level. Moisture level in the pollen can be decreased by exposing the pollen to diluted salt solutions, silica gel and dry air or by chemical treatment with vitrification solutions.

### Field gene banks

Field gene banks are gene banks based around the management of live specimens, in contrast to a seed bank which is focused on the facilitation of backups of germplasm, typically in the form of seeds. Field gene banks are vulnerable to natural disasters, pests and disease. As such, they are typically used as a method of last resort if a species cannot be preserved via normal means, such as if it didn't produce seeds. This method uses more land, energy and water than other methods.

## Facilities

* The Centre for Pacific Crops and Trees (CePaCT) plant gene bank in Suva, Fiji, focuses on propagating (and re-propagating) seedlings of plants (using clippings and tissue culture, rather than as seeds), to preserve the genetic diversity of the most important varieties of food crops of the Pacific region, such as banana, taro, breadfruit and yam.