When a cyclone hit the island of Fiji in 2016, a high priority was the food security of the population. The local government requested urgent help from a center thousands of kilometers away, in Lima.
The International Potato Center (CIP), based in the Peruvian capital, responded by sending Fiji a message of hope in the form of tiny seedlings in test tubes, allowing the Pacific archipelago to restart production of an essential crop.
This story clearly shows why it is crucial that copies of the planet’s biodiversity are safely stored.
Conventional seed banks serve that purpose. The 2 largest, the London Botanic Garden Millennium Seed Bank, Kew Gardens, and the underground chamber in the Norwegian Arctic, in Svalbard, have been working for years precisely to safeguard key species in the event of a local or global catastrophe.
But there is a big problem. Many plants essential for the sustenance of humanity and the survival of ecosystems not can be conserved in these traditional seed banks.
Crops as important as potatoes, sweet potatoes, bananas, cocoa, coffee, citrus fruits, and also about half of the trees in the Amazon, among other species, require another very long-term security route: the so-called “cryobanks”.
These centers use extreme cold preservation techniques or “cryopreservation” to keep safe copies of biodiversity treasures. And doing so is more necessary than ever due to species extinction, habitat loss and climate change.
At BBC Mundo we talk to experts in cryopreservation who explain what the technique consists of, how advanced it is in Latin America and why it is crucial to invest in it for the future.
Buds and seeds: what plants are stored in cryobanks
“Cryobanks are, as the word indicates, banks in which we store valuable resources at the temperature of liquid nitrogen, that is of 196° below zero. It is a temperature about 10 times lower than that of the freezer or freezer in a conventional refrigerator, ”conservation biologist Daniel Ballesteros, an expert in cryopreservation and professor at the University of Valencia, explained to BBC Mundo.
Until recently, Ballesteros worked in cryopreservation at Kew Gardens, which has a cryobank in the same building as the Millennium Seed Bank.
The scientist pointed out that there 3 cases of plants that require cryopreservation because they are not suitable for traditional seed banks.
one-The first case is that of crops that simply they are not propagated by seedssuch as potatoes and bananas.
In these cases the propagation is “clonal”, since identical copies are produced from a small part of the plant.
Engineer Rainer Vollmer, Cryopreservation officer at the International Potato Center in Lima, explained to BBC Mundo what clonal propagation consists of.
“The tuber of a potato has buds, which in the language of traditional farmers are known as eyes: it is where the plant begins to sprout.”
“If you cut a potato into several parts, and each part has an eye, those parts have the ability to generate other plants that are clones, identical in their DNA,” Vollmer said.
two-The second case of plants that require cryobanks is that of plants that do produce seeds, but these are “recalcitrant”, as those that they do not tolerate being dried with usual methods.
In conventional seed banks, so that the seeds last as long as possible, they are dried “until their internal water content is around 3 to 7%,” explained Ballesteros. And then they are preserved at about 20 degrees below zero.
“But in the case of recalcitrant seeds, what happens is that when they are dried below 20% water content they die.” Storing them without drying is also not an option as they die quickly.
3-The third case of plants that require cryopreservation is that of crops such as coffee, citrus or papaya, as well as many orchids, whose seeds are not recalcitrant and can dry out below 20% water content. But when stored at 20 degrees below zero have longevity issues And they deteriorate very quickly.
“50% of the trees in the Amazon”
Daniel Ballesteros is mainly concerned with the case of recalcitrant seeds.
“In the field of agriculture there is a certain development of cryopreservation,” he said.
“But in the case of wild species there are very few initiatives, there is practically nothing and that is where we should put more focus.”
“Consider that about half of the trees in tropical rain forests, such as the Amazon, produce recalcitrant seeds“.
Other cases of recalcitrant seeds, the scientist pointed out, are cocoa and trees such as oaks, which are of great economic importance in Spain for producing not only cork but also the acorns that feed pigs for Iberian ham.
Hugh Pritchard, an expert in cryopreservation at the London Botanic Garden, told BBC Mundo that “it is estimated that about a third of tree species globally produce recalcitrant seeds (of about 60,000 known tree species)”.
And in general, “perhaps 10% of all plant species in the world produce such seeds. We would then be talking about 35,000 to 40,000 species”.
A safe for the planet in Lima
The International Potato Center in Lima is a worldwide reference. It has the most diverse bank of germplasm (material from which a plant can be produced) of potatoes, sweet potatoes and other Andean roots and tubers in the world.
“In the case of potatoes, we have more or less 4,500 native varieties that have evolved hundreds and even thousands of years in Peru. We also keep some 5,000 native varieties of sweet potato or sweet potato.”
CIP also preserves collections of what are known as wild potatoes, which represent some 145 species.
“They are wild relatives of cultivated potatoes that generally produce very small tubers or no tubers at all.”
They are generally not suitable for human consumption, Vollmer said, but they are very valuable because they have genes for resistance to cold, water stress, salinity and disease.
Most of the varieties at CIP are not kept in the cryobank but rather in the large “in vitro” germplasm bank, that is, in thousands of small test tubes that each contain a small plant or seedling.
“We could say that this in vitro conservation is medium-term conservation, but it has the disadvantage that this material must be continually renewed because it ages. Renewing means cutting the stem into segments, each segment containing 1-3 buds. When these segments are introduced into a new tube with sterile culture medium, another young plant grows from one of these buds”.
“And every time the material is renewed there are risks, because the human being makes a mistake and the plant becomes stressed over time and there may be mutations in this continuous renewal.”
It is because of that more than 4,000 varieties are also preserved in the CIP cryobankwhich according to Vollmer offers great advantages.
In addition to not requiring the renewal of potato seedlings every 2 or 3 years, or in the case of sweet potatoes, every six to twelve months, the cryobank offers “really long-term conservation, of hundreds of years or more. Theoretically there are no shelf life limitations“.
“And another great advantage is that it is a very space-efficient option. Imagine that in a cubic meter we could conserve up to 180,000 potential plants”.
Potential babies: how is cryopreservation done in practice?
Vollmer explained that in the case of the potato “what is used is a small part of the plant, the last bud on the tipwhich is called the apical bud.
“From each plant a single bud is cut, which measures about a millimeter, and then ten of these buds are placed on a piece of aluminum foil in a chemical solution called a cryoprotectant solution.”
“And that is abruptly introduced to liquid nitrogen.”
“When the material is wanted, it is thawed again and placed in a special recovery medium. Between 30 to 60 days after thawing, you already have a complete plant“.
In the case of recalcitrant seeds, “what we do is that we only extract from the seed the portion that generates the new plant, that is, the embryo or embryonic axis,” said Ballesteros.
“If you open an oak acorn you have two very large valves and in the middle a tiny point. All those little tips of the acorn, or of a pea or of an almond, are embryos”.
“In cryopreservation we work with those embryos.Seeds are potential little babies.”.
Ice is the great enemy
The great challenge in cryopreserving seeds is how to freeze the embryos without ice formation.
“As we cannot dry it out, the seed will contain water. And if we freeze it, that water forms ice and the ice breaks the tissues and kills the seed”, Ballesteros explained.
The goal is to make the embryos solid but without forming ice, transforming into a glass-like substance.
One way to accomplish that is to cool the cells very slowly.
“That way, ice forms in the middle, outside the cell. Then the cell that has a lot of water notices that ice formation as a sign that the environment outside is getting dehydrated and expels the water that it has inside. There is an internal dehydration process and then what is done is to freeze very quickly”.
“The other way to vitrify is that instead of freezing slowly at first, you freeze the whole tissue very, very quickly so that the water within that tissue doesn’t crystallize but instead solidifies into glass.”
Cryobanks in Latin America
Cryopreservation was first used for animal eggs or semen and moved to plants in the 1980s, but botanical cryobanks are not yet widespread.
In Belgium, for example, is the main banana cryobank.
Y in Latin America, the largest is the International Potato Center.
“Unfortunately, at this scale, we are the only ones in the region,” Vollmer noted.
“There are smaller initiatives from universities or centers such as INTA in Argentina, or EMBRAPA in Brazil, but all on a small scale.”
The International Potato Center is one of 15 institutions that make up the CGIAR, an international consortium of research centers for food security.
“In a new initiative, we have now been chosen for our experience to create a network of cryopreservation centers in Latin America. The idea is to promote the conservation of valuable biodiversity with this technique, but we are just getting started”.
“Everything also depends on the will of each country, whether they want to invest in it, whether they consider it a priority.”
Although cryopreservation requires a high initial investment in equipment and training, the subsequent operating cost is relatively low, according to experts consulted by BBC Mundo.
For Vollmer, “if you already have an in vitro laboratory, I would estimate that with $20,000 you can implement a cryopreservation program on a very small scale (including tanks, supplies, chemicals, etc.)”.
“After a conservation time of approximately 9 to 10 years, cryopreservation becomes cheaper than in vitro conservation. for not requiring such continuous renewal and for saving space”.
Ballesteros pointed out on the other hand that “in many tropical countries there are already laboratories that could simply be enriched, in addition to training people in cryopreservation.”
“A race against extinction”
“The cryopreservation is the conservation method of the future“, assured Rainer Vollmer.
“We are in a race against the extinction of many species. It is very sad that due to the intervention of the human being, the destruction of the environment and changes in climatic conditions, many plants can no longer exist in natural conditions”.
“Some samples that we have in the CIP bank, for example, no longer exist in nature.”
For Daniel Ballesteros, although plants must be preserved in their native environment protected, for example, in natural parks, seed banks and cryobanks are still essential.
“We can create natural parks in the Congo, in Colombia or in Brazil to conserve tropical forests, because we do have to conserve plants ‘in situ’, on the ground.”
“But we also want a backup, because all these species are threatened and the place where they live may disappearwe can see it in the Amazon”.
“If a species disappears, we will never have it again, unless we have these cryobanks to be able to reinstate them,” Ballesteros told BBC Mundo.
“When we talk about banks, in general, we talk about money. But we don’t have all the necessary backups for our most valuable resource, which is nature.”
It may interest you:
* Scientists will freeze koala sperm to save them from extinction
* 3 ethical issues surrounding pig heart transplants in humans
* The 200 frozen corpses in an Arizona laboratory waiting for science to resurrect them
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