Seed banks: storing seeds to preserve diversity
An extraordinary feature of seeds is that they can remain viable for long periods of time, which means they can wait until the time’s just right to emerge and grow. This also means that we can store them in facilities called “seed banks” to capture and preserve the genetic diversity that exists in nature. Noam Chayut manages just such a seed collection at the John Innes Centre in Norwich, and spoke with Chris Smith...
Noam - Our seed bank - or gene bank as we prefer to call it usually - is just a very big room, about 600 cubic metres of stable cold environment. It's only four degrees and very dry. So the main thing with preserving longevity of seeds is that dryness, we keep our seeds in envelopes made of paper so the air can flow through them and maintain the humidity very low, below 10% of relative humidity.
Chris - So a person walking through a seed bank would just see rows and rows basically of neat envelopes containing seeds of different species of plants?
Noam - Yes. So some gene banks would hold big freezers because you can also freeze seeds. Ours would just be a very big room of shelves with brown envelopes of seeds in fact, yes.
Chris - And how do you choose the seeds?
Noam - So we have in our custodianship over 45,000 different kinds of diversity of strategic UK crops, that's mainly wheat, barley, oats, peas, and some brassicas. And from each of them, we have many, many, many thousands of different kinds, different cultivars, different wild relatives of them that can be used in plant science and in breeding.
Chris - Have you got a sort of a database on each of the collections of seeds? So you can say, well, this one looks like this, and there's a photo of the plant and what its traits are, perhaps its DNA sequence to go with. Is that how you process them?
Noam - Yeah. So the other side of a gene bank is the databases. And it is just as important as the seeds, of course. Because we need to choose them for a project or for any purpose. So we have a database called Seed Store in our case that contains exactly that information, as you mentioned.
Chris - And the nuts and bolts of actually getting the seed samples into the seed bank in the first place? Is that as laborious as it sounds, someone goes out with that envelope and just shakes a flower head and gets some seeds! And then what do they do with them?
Noam - So, yes many of the seeds sourced in expeditions around the world to collect wild diversity or traditional cultivars, some of our collections are very important because they were collected about a hundred years ago just before the industrial agriculture kicked in to generate more uniformed varieties that are grown today. And the diversity that is kept in this collection enabled a lot of the work that we are doing in the study of plant science and improving crops.
Chris - And how do you know, if you take some of those seeds from a hundred years ago, that A) they're viable and B) that we're not ending up changing them by storing them?
Noam - It's a very good question because evolution never stops. And it continues when we grow them in agriculture. And also when we grow them for gene banking purposes. We do regenerate them or rejuvenate the collection every two or three decades, or when they are depleted in term of stocks. We have ways to prolong their longevity, but we can't stop the deterioration. So in the end, the only way to check if a seed is viable is to put it in soil, water it and get the plant. But we have measures to protect it from gene flow from others. So we try to protect it as unique as it was.
Chris - You mean, so that when it's growing in the greenhouse, for example, there isn't the accidental pollination by a more modern species or another species that could introduce foreign DNA in there.
Noam - Exactly that. So we separate the flowers in some crops. In others we separate the whole plant. Exactly.
Chris - Can you get all of them to grow? Are there any that you end up storing and then you discover they just don't store and they won't grow?
Noam - So the science of conservation is relatively new. It's only half a century and there is not a lot of empiric information. We have a lot of theory that helps us to predict how long a seed would preserve themselves in certain conditions from different species of different kinds of seeds. But in the end, it's our responsibility as custodians of the collection to quality check them every so often, to make sure that they are viable and if not to rejuvenate them and maintain them viable for usage.
Chris - And while it's wonderful to have this, what are you actually going to do with it? What's its broader function in the long term?
Noam - So there is kind of a notion in the public about seed banks that they are there for a kind of a doomsday scenario to restore lost things. And that's a minor part of it. But we are - our bread and butter work - we are part of the chain that brings bread to the supermarkets and other crops to our shelves. We produce diversity, the raw material for plant breeders to improve crops and diversity that underpins plant science. And we do it daily. We send hundreds of samples yearly to end users.
Chris - Later on in the program, we're going to talk to somebody who has actually grown a date from a 2000-year-old preserved date stone. I bet you haven't got a seed as old as that!
Noam - No, no, our seeds are much younger and they date some decades back, as crops can do. But this is a famous and very exciting story in the field, absolutely.