Banking on seeds

Some of our most valuable treasures are frozen in vaults around the world, waiting for a time when they may be needed.

 
  Four bean varieties in storage at the CIAT gene bank in Colombia.   Neil Palmer/Flickr  (CC BY-SA 2.0)

Four bean varieties in storage at the CIAT gene bank in Colombia. Neil Palmer/Flickr (CC BY-SA 2.0)

 

The richest banks in the world don’t contain money, gold or jewels. Instead, they hold millions of years of information, and some of mankind’s greatest engineering achievements, all in the form of tiny seeds. Without a doubt, seeds are one of the most important resources on earth — they provide food, shelter, medicine, clean air and so much more.

The primary function of a seed bank is to provide ‘back up’ material should the source material become lost due to disease, natural disasters, formation of genetic hybrids, invasive species, climate change or human interaction. By preserving as many seeds as possible, we can remember the past, preserve the present and save the future.

Only last year, we saw why long term storage of seeds is absolutely crucial. Due to the ongoing Syrian Civil War, seeds at the International Center for Agricultural Research in the Dry Areas — based in Aleppo, Syria — became inaccessible to researchers. A new seed bank was established in Lebanon by extracting seeds from long-term storage in the Svalbard Global Seed Vault, located on the remote Norwegian island of Spitsbergen.

Seed banks can be found all over the world; the most notable examples include Kew’s Millennium Seed Bank (England), the Center for Agricultural Resources Research (United States), the Vavilov Research Institute (Russia), Navdanya (India) and the Australian PlantBank.

 
  The entrance (left) and interior of the Svalbard Global Seed Vault on the island of Spitsbergen, Norway.   Bjoertvedt/Wikimedia Commons  (CC BY-SA 3.0);  NordGen, Dag Terje Filip Endresen/Wikimedia Commons  (public domain)

The entrance (left) and interior of the Svalbard Global Seed Vault on the island of Spitsbergen, Norway. Bjoertvedt/Wikimedia Commons (CC BY-SA 3.0); NordGen, Dag Terje Filip Endresen/Wikimedia Commons (public domain)

 

The protocols for maintaining seed banks are carefully outlined by the Food and Agriculture Organization of the United Nations. Seeds are first dried in a controlled environment of 5-20ºC and 10-25% relative humidity, then sealed in an airtight container to maintain moisture content. The dried seeds are then maintained at low temperatures. Just as keeping food in a fridge or freezer extends its life, the seeds are preserved because their metabolic functions and biochemical processes are slowed down.

The majority of seed collections are kept in cold rooms at around -18ºC and 15% relative humidity. Because it’s best to avoid disrupting the seeds once they’re in long-term storage, some are set aside during the preservation process for medium-term storage. Seeds in medium-term storage (kept at 5-10ºC) are used for viability testing, regeneration (should viability drop), and characterisation (to identify morphological, physiological or agronomical features).

The viability of seeds varies from species to species, and is greatly affected by drying methods and storage conditions. Seeds kept in short-term storage (below 25ºC) should last for at least eight years. For orthodox seeds in medium-term storage, viability is expected to last 30 years. Long-term storage can provide high quality seeds for even longer periods of time, perhaps centuries, but exactly how long is hard to predict in the absence of long-term experiments. The oldest seed successfully regenerated was reportedly 32,000 years old, frozen in Siberian permafrost — a natural seed bank.

Each seed bank sets its priorities for conservation based on several criteria. Native seeds often rank very highly, especially if they are economically or culturally important to their country of origin. Many seed banks also collect and conserve wild crops with important traits for breeding, as well as those with medicinal, recreational and agricultural uses.

 
  Different varieties of economically important crops, such as wheat, are given high priority in seed banks.   Dave Gunn/Flickr  (CC BY-NC 2.0)

Different varieties of economically important crops, such as wheat, are given high priority in seed banks. Dave Gunn/Flickr (CC BY-NC 2.0)

 

It is also important to preserve endangered species, since we often know very little about them — with further research, what is currently an endangered species could become an economically important plant. Preserving the genetic diversity of these species also gives them a better chance at surviving changing environments as a result of human interaction, invasive species and climate change. One example is the American elm, which has suffered great losses due to Dutch elm disease. By preserving seeds and screening individuals, those that are resistant or tolerant to the disease can be identified and used for breeding or cloning.

Although there are multiple seed banks scattered across the globe, and thousands of species preserved, there is still much work to do. Kew’s Millennium Seed Bank and their global partners hope to save 25% of the world’s species (75,000 species) by 2020. That still leaves over 225,000 species to preserve, and that number continues to grow as new and hybrid species are discovered. Fortunately, the importance of seed banks is increasingly being recognised, and, at the national level, more and more governments are putting funding into such projects. In addition, the Consultative Group for International Agricultural Research (CGIAR) recently presented the new Genebanks Platform proposal for 2017-2022, ensuring that strong financial, technical and advisory support will be provided to 11 research centres in the CGIAR network.

From a research perspective, there’s still a lot we don’t know about seed conservation. One difficulty is the issue of unorthodox or recalcitrant seeds. These seeds — which include avocado, mango, coconut and cocoa — cannot be dried and frozen using standard methods, due to physiological and chemical differences, such as large size or high water content. More research into molecular characterisation of seeds for breeding purposes is also needed. This would help determine genetic markers associated with specific traits of interest, allowing for more targeted use of seed bank collections for breeding programs.

Seed banks are currently the safest and most efficient way to preserve genetic diversity in plants. For those invested in the field of science, the value of that is immeasurable. People will continue to value money, gold and jewels, but there is also incredible value in a tiny seed. And you can take that to the bank!

Edited by Andrew Katsis and Ellie Michaelides