Seedbank at the USDA Western Regional Plant Introduction Station
Seedbank at the USDA Western Regional Plant Introduction Station

A seed bank (also seed banks or seeds bank) stores seeds to preserve genetic diversity; hence it is a type of gene bank. There are many reasons to store seeds. One is to preserve the genes that plant breeders need to increase yield, disease resistance, drought tolerance, nutritional quality, taste, etc. of crops. Another is to forestall loss of genetic diversity in rare or imperiled plant species in an effort to conserve biodiversity ex situ. Many plants that were used centuries ago by humans are used less frequently now; seed banks offer a way to preserve that historical and cultural value. Collections of seeds stored at constant low temperature and low moisture are guarded against loss of genetic resources that are otherwise maintained in situ or in field collections. These alternative "living" collections can be damaged by natural disasters, outbreaks of disease, or war. Seed banks are considered seed libraries, containing valuable information about evolved strategies to combat plant stress, and can be used to create genetically modified versions of existing seeds. The work of seed banks often span decades and even centuries. Most seed banks are publicly funded and seeds are usually available for research that benefits the public.

Storage conditions and regeneration

Seeds are living plants and keeping them viable over the long term requires adjusting storage moisture and temperature appropriately. As they mature on the mother plant, many seeds attain an innate ability to survive drying. Survival of these so-called 'orthodox' seeds can be extended by dry, low temperature storage. The level of dryness and coldness depends mostly on the longevity that is required and the investment in infrastructure that is affordable. Practical guidelines from a US scientist in the 1950s and 1960s, James Harrington, are known as 'Thumb Rules'. The 'Hundreds Rule' guides that the sum of relative humidity and temperature (in Fahrenheit) should be less than 100 for the sample to survive five years. Another rule is that reduction of water content by 1% or temperature by 10 °F (5.6 °C) will double the seed life span. Research from the 1990s showed that there is a limit to the beneficial effect of drying or cooling, so it must not be overdone.

Understanding the effect of water content and temperature on seed longevity, the Food and Agriculture division of the United Nations and a consultancy group called Bioversity International developed a set of standards for international seed banks[1] to preserve seed longevity. The document advocates drying seeds to about 20% relative humidity, sealing seeds in high quality moisture-proof containers, and storing seeds at −20 °C (−4 °F). These conditions are frequently referred to as 'conventional' storage protocols. Seeds from our most important species – corn, wheat, rice, soybean, pea, tomato, broccoli, melon, sunflower, etc. – can be stored in this way. However, there are many species that produce seeds that do not survive the drying or low temperature of conventional storage protocols. These species must be stored cryogenically. Seeds of citrus fruits, coffee, avocado, cocoa, coconut, papaya, oak, walnut and willow are a few examples of species that should be preserved cryogenically.

Like everything, seeds eventually degrade with time. It is hard to predict when seeds lose viability and so most reputable seed banks monitor germination potential during storage. When seed germination percentage decreases below a prescribed amount, the seeds need to be replanted and fresh seeds collected for another round of long-term storage.[2]

Seeds banks may operate in much more primitive conditions if the aim is only to maintain year-by-year seed supplies and lower costs for farmers in a particular area.[3]

Challenges

One of the greatest challenges for seed banks is selection. Collections must be relevant and that means they must provide useful genetic diversity that is accessible to the public. Collections must also be efficient and that means they mustn't duplicate materials already in collections.

Keeping seeds alive for hundreds of years is the next biggest challenge. Orthodox seeds are amenable to 'conventional' storage protocols but there are many seed types that must be stored using nonconventional methods. Technology for these methods is rapidly advancing; local institutional infrastructure may be lacking.

Some seeds cannot be kept alive in storage and must be regenerated – planted to produce a new quantity of seeds to be stored for another length of time.[4][5] Parzies et al. 2000 found that this reduced the effective population size and alleles were lost.[4][5] Parzies' finding has since been taken seriously by banks around the world and has sparked further verification – regeneration is widely recognized to not preserve diversity perfectly.[4][5]

Alternatives

In-situ conservation of seed-producing plant species is another conservation strategy. In-situ conservation involves the creation of National Parks, National Forests, and National Wildlife Refuges as a way of preserving the natural habitat of the targeted seed-producing organisms. In-situ conservation of agricultural resources is performed on-farm. This also allows the plants to continue to evolve with their environment through natural selection.

An arboretum stores trees by planting them at a protected site.

A less expensive, community-supported seed library can save local genetic material.[6]

The phenomenon of seeds remaining dormant within the soil is well known and documented (Hills and Morris 1992).[7] Detailed information on the role of such "soil seed banks" in northern Ontario, however, is extremely limited, and research is required to determine the species and abundance of seeds in the soil across a range of forest types, as well as to determine the function of the seed bank in post-disturbance vegetation dynamics. Comparison tables of seed density and diversity are presented for the boreal and deciduous forest types and the research that has been conducted is discussed. This review includes detailed discussions of: (1) seed bank dynamics, (2) physiology of seeds in a seed bank, (3) boreal and deciduous forest seed banks, (4) seed bank dynamics and succession, and (5) recommendations for initiating a seed bank study in northern Ontario.

Longevity

Main article: Oldest viable seed

Seeds may be viable for hundreds and even thousands of years. The oldest carbon-14-dated seed that has grown into a viable plant was a Judean date palm seed about 2,000 years old, recovered from excavations at the palace of Herod the Great in Israel.[8]

In February 2012, Russian scientists announced they had regenerated a narrow leaf campion (Silene stenophylla) from a 32,000-year-old seed. The seed was found in a burrow 124 feet (38 m) under Siberian permafrost along with 800,000 other seeds. Seed tissue was grown in test tubes until it could be transplanted to soil. This exemplifies the long-term viability of DNA under proper conditions.[9]

Climate change

Conservation efforts such as seed banks are expected to play a greater role as climate change progresses.[10] Seed banks offer communities a source of climate-resilient seeds to withstand changing local climates.[11] As challenges arise from climate change, community based seed banks can improve access to a diverse selection of locally adapted crops while also enhancing indigenous understandings of plant management such as seed selection, treatment, storage, and distribution.[12]

Facilities

Plant tissue cultures being grown at a USDA seed bank, the National Center for Genetic Resources Preservation
Plant tissue cultures being grown at a USDA seed bank, the National Center for Genetic Resources Preservation

There are about 6 million accessions, or samples of a particular population, stored as seeds in about 1,300 genebanks throughout the world as of 2006.[13] This amount represents a small fraction of the world's biodiversity, and many regions of the world have not been fully explored.

Seed banks classification

Seed banks can be classified in three main profiles: assitentialist, productivist or preservationist. Many of them can belong to more than one category.[26]

Seed banks classification by profile
Profile Assitentialist Productivist Preservationist
Objective Conserve varieties of seeds in case they need to be used in coming harvests Conserve varieties of seeds to contribute to the improvement of current crops by crossing them with those seeds Preserve varieties of seeds in case they are destroyed by either man or natural events.
Functioning The bank provides seeds to farmers who lack them The bank makes its seeds available to produce new crops of agricultural interest from these seeds The bank does not offer its seeds but it safeguards them

Early concepts

In Zoroastrian mythology, Ahura Mazda instructed Yima, a legendary king of ancient Persia, to build an underground structure called a Vara to store two seeds from every kind of plant in the known world. The seeds had to come from plant specimens that were free of defects, and the structure itself had to withstand a 300-year apocalyptic winter.[27] Some scholars have suggested that the Norse equivalent of this myth is the underground garden Odainsaker, which was intended to withstand the three-year fimbul winter preceding Ragnarok, to protect the people (and seemingly the plants) that would repopulate the world after this event.[28]

See also

References

  1. ^ http://www.fao.org/docrep/019/i3704e/i3704e.pdf[bare URL PDF]
  2. ^ Hong, T.D. and R.H. Ellis. 1996. A protocol to determine seed storage behaviour. IPGRI Technical Bulletin No. 1. (J.M.M. Engels and J. Toll, vol. eds.) International Plant Genetic Resources Institute, Rome, Italy. ISBN 92-9043-279-9 [1]
  3. ^ "The gatekeepers of Mozambique's community seed banks". UN FAO (Food and Agriculture Organization of the United Nations). Retrieved 2021-09-14.
  4. ^ a b c van de Wouw, Mark; Kik, Chris; van Hintum, Theo; van Treuren, Rob; Visser, Bert (2009-10-19). "Genetic erosion in crops: concept, research results and challenges". Plant Genetic Resources. NIAB (National Institute of Agricultural Botany) (CUP). 8 (1): 1–15. doi:10.1017/s1479262109990062. ISSN 1479-2621. S2CID 54496219.
  5. ^ a b c Spooner, David; Treuren, Rob van; Vicente, M. C. de (2005). Molecular markers for genebank management. Rome, Italy: International Plant Genetic Resources Institute (IPGRI). pp. viii+126. hdl:10113/11672. ISBN 978-92-9043-684-3. OCLC 136956590. S2CID 83426985. NADLC# 11672. AGRIS id QJ2007000031. Bioversity PDF. CGIAR hdl:10568/104976.
  6. ^ "Nurturing plant legacies: Two groups lend seeds and plants to gardeners".
  7. ^ Hills, S.C.; Morris, D.M. 1992. The function of seed banks in northern forest ecosystems: a literature review. Ont. Min. Nat. Resour., Ont. For. Res. Instit., Sault Ste. Marie ON, For. Res. Inf. Pap., No. 107. 25 p.
  8. ^ National Geographic
  9. ^ Frier, Sarah (2012-02-20). "32,000-Year-Old Plant Reborn From Ancient Fruit Found in Siberian Ice". Bloomberg.
  10. ^ Griffiths, Kate (April 2015). "Maximizing the phylogenetic diversity of seed banks". Conservation Biology. 29 (2): 370–81. doi:10.1111/cobi.12390. PMID 25196170.
  11. ^ Maharjan, Shree (February 2018). "Roles and contributions of community seed banks in climate adaptation in Nepa". Development in Practice. 28 (2): 292–302. doi:10.1080/09614524.2018.1418838. S2CID 158910274.
  12. ^ Vernooy, Ronnie (April 2017). "The roles of community seed banks in climate change adaption" (PDF). Development in Practice. 27 (3): 316–327. doi:10.1080/09614524.2017.1294653. S2CID 157455756.
  13. ^ Rajasekharan, P. E. (2015-01-01). "Gene Banking for Ex Situ Conservation of Plant Genetic Resources". In Bahadur, Bir; Rajam, Manchikatla Venkat; Sahijram, Leela; Krishnamurthy, K. V. (eds.). Plant Biology and Biotechnology. Springer India. pp. 445–459. doi:10.1007/978-81-322-2283-5_23. ISBN 9788132222828.
  14. ^ "Archived copy". www.cnn.com. Archived from the original on 11 February 2007. Retrieved 12 January 2022.((cite web)): CS1 maint: archived copy as title (link)
  15. ^ a b c d Drori, Jonathan (May 2009). "Why we're storing billions of seeds". TED2009. TED (conference). Archived from the original on 2011-12-08. Retrieved 2011-12-11.
  16. ^ UK Millennium Seed Bank Project Archived 2008-07-06 at the Wayback Machine
  17. ^ "Archived copy". Archived from the original on 2013-06-01. Retrieved 2012-10-02.((cite web)): CS1 maint: archived copy as title (link)
  18. ^ David Ehrlich (July 27, 2022). "'One Man Dies a Million Times' Review: A Haunting Portrait of Preservation at the End of the World". Indiewire. Retrieved August 2, 2022.
  19. ^ Save the Seeds Movement of the Uttarakhand Himalayas, India Archived June 30, 2015, at the Wayback Machine
  20. ^ National Center for Genetic Resources Preservatio Archived November 12, 2011, at the Wayback Machine
  21. ^ "Desert Legume Program (DELEP) | Home".
  22. ^ "National Center for Plant Genetic Resources of Ukraine - Інститут рослинництва ім. В. Я. Юр'єва НААН". yuriev.com.ua. Retrieved 2022-05-18.
  23. ^ "Військові рф повністю знищили єдиний в Україні генетичний банк рослин". www.ukrinform.ua (in Ukrainian). Retrieved 2022-05-18.
  24. ^ "Ukraine's agricultural research is threatened by the war". economist.com. Retrieved 2022-05-18.
  25. ^ Salinier, Jérémy; Lefebvre, Véronique; Besombes, Didier; Burck, Hélène; Causse, Mathilde; Daunay, Marie-Christine; Dogimont, Catherine; Goussopoulos, Juliette; Gros, Christophe; Maisonneuve, Brigitte; McLeod, Louis (2022-01-27). "The INRAE Centre for Vegetable Germplasm: Geographically and Phenotypically Diverse Collections and Their Use in Genetics and Plant Breeding". Plants. 11 (3): 347. doi:10.3390/plants11030347. ISSN 2223-7747. PMC 8838894. PMID 35161327.
  26. ^ Pellegrini, Pablo A.; Balatti, Galo E. (2016-12-01). "Noah's arks in the XXI century. A typology of seed banks". Biodiversity and Conservation. 25 (13): 2753–2769. doi:10.1007/s10531-016-1201-z. ISSN 1572-9710. S2CID 2545366.
  27. ^ Avesta, Vendidad, Fargard 2:24-28
  28. ^ Teutonic Mythology by Viktor Rydberg (1906), v. 1, p. 307-43; v. 2, p. 380-89

Further reading