The Mighty Spud - Sandy Knapp, Glenn Bryan and Susan Calman

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1:04BBC Sounds. Music, radio, podcasts. Hello, I'm Brian Cox. And I'm Robin Ince, and this is the Infinite Monkey Cage. Now, Douglas Adams has been a great influence on many of us, and, in fact, for instance, you'll rarely find Brian without a towel. He always has a towel, sometimes little more, as subscribers of his OnlyFans site will know. quantum's quarks, quips and sometimes nips. You didn't go for the obvious pun then. No, originally I was going to say OnlyFans site where he answers the most difficult questions about physics and it's known as hard... But anyway, so the art of flying is one of my favourite Douglas Adams philosophy.

1:47The art of flying is throwing yourself to the ground and missing. The ships hung in the sky in much the same way as bricks don't. and most importantly, it is a mistake to believe you can solve any problem just with potatoes. But tonight we're asking, is that really a mistake? Finally, at episode 204, we deal with the potato. I mean, more specific, the science of the potato. Well, they'll know it's going to be there, we don't know. They know it's going to be the science, we've been doing that for ages, haven't we? But it might get philosophical as well. You burnt yourself on a chip once, do you remember?

2:24We could talk about that. That's not philosophical. Why is that philosophical? Your ability to understand the heat death of the universe, but not the speed of the cooling of a chip. It's actually related. Because we have to ask yourself the question, what is temperature? It's a thing you can measure on a thermometer, but that doesn't tell you at a deep level what it is. You have to know that everything's made of atoms to really know what temperature is. It's a measure of the speed that things are jiggling around. The usefulness of... I'll stop... Yeah. When did we start eating potatoes? How and where did they evolve?

2:55Is it possible, and of course the answer will be yes, to fill an entire episode of the BBC's flagship radio science programme and podcast with a discussion of the science of the potato? So to help us find out, we are joined by a Bannock russet botanist, a Marist Piper molecular geneticist and a Jersey royal jester. And they are... I'm Sandy Knapp. I'm a botanist from the Natural History Museum. And my favourite vegetable, besides a potato, of course, could be a tomato, but that's a fruit. It's the Jerusalem artichoke. That is the greatest artichoke response that has ever occurred. I'm Glenn Bryan and I'm a molecular geneticist and for 30 years I studied potato genetics at the James Hutton Institute in Scotland.

3:41A root vegetable that I'm very fond of is almost as good as the potato is the parsnip because I'm really fond of the roast parsnip. I also love my wife's delicious curried parsnip soup. Not quite up there with artichokes, let's see what happens next. I'm Susan Kalman and I have absolutely no scientific qualifications to be here at all, but I do love the potato in all of its glorious forms. My other favourite root vegetable is not as classy as the artichoke, it is the humble carrot, which I believe is versatile and beautiful, but I will never accept it in a cake. And this is our panel.

4:30I'd like to ask for a definition, actually, just because you mentioned you can't use tomato because it's a fruit. So what's the definition of a vegetable? A vegetable is something that's not a fruit. That doesn't... Not allowed. Fruits have seeds and vegetables don't. So an aubergine has seeds, or it used to before we did things to them to make them not have seeds. And tomatoes have seeds, but potatoes don't. So the aubergine is also a fruit? Yes. As is a cucumber and courgettes, but not carrots or parsnips or Jerusalem artichokes. But real artichokes are a flower bud. I don't even know what she's seeing anymore.

5:13So what's the definition of a potato then? A potato is, Glenn's probably better at this than I am, well a potato is a growth from an underground root of a plant that's used to store starch. So potato plants use potatoes to store starch so that they can last through the long cold winters in the Andes. So they're really, potatoes are definitely not there for us, but we've really done quite a lot with them. And technically the tuber forms on an underground stem. the main stem of the potato plant grows up and the stolons come off of the stem below the ground and the tubers form at the end of those stolons.

5:49So the stolon is really an underground stem, not strictly a root, and there are roots as well. So that's why when you plant potatoes in plastic bags, which is actually the tried and true way to plant potatoes in a small London garden, is you put potatoes in the bottom and you put a bit of soil on and you wait till they come up and then you put more soil on because that makes them make all those things, the underground stems to the side. I take my chitting very seriously and I'm saying the word chit, by the way, before anyone writes in. Very, very good, Susan. I chit my potatoes in old egg boxes until they're ready to put in.

6:21Ready to go. And chitting is... Well, chitting is the process, but listen to me. So you chit them so they're ready to plant because when you buy the potatoes, if you're going to grow your own potatoes, you don't just put the potatoes on the ground, you have to let them, you know, chit. And so if you put them in egg cups, it's perfect and then all the things. I mean, I'm surmising what he's about to say more. The bits come out. And then when the bits come out, they're ready to go in and you put the earth on it. Yeah, that's good. And then eventually when you take it all out, there's more potatoes.

6:55One more clarification, because Glenn, you said something, that you said it's not technically a root. So the question is, what is the difference between a stem and a root? How is the potato not technically... Because it looks like it's on a root, doesn't it? But you're saying it's not a root? It's different from, say, a sweet potato. A sweet potato is also a tuber, but it forms on a root. It's part of the root. You know, the root swells and forms a sweet potato. But with a potato, they have roots, which are like normal roots, and they have these underground stolons, which come off of the main stem, and they're like a rhizome.

7:28And then at the end of those stolons, the tubers, you know, they swell and then the tubers form. So they're separate from the roots. So a stolon is an underground stem? It's an underground stem, and it usually runs kind of parallel to the substrate, so it grows kind of outwards, just under the ground. And they will come out of the ground sometimes. If you put them in pots, for example, the stolons will wander, so they'll come out of the pot, and then they will start to grow a new plant. So instead of growing a tuber, they'll grow a new plant once they get into the light, and they will wander into the next pot.

8:00So you have to be very careful when you're growing potatoes for research that you don't get these wandering stolons, because you might end up with tubers in the next pot that come from the pot next door. But what's great is you can have wandering stolons in the garden. Susan, do you have wandering stolons? But you can also cut through. Yes, I think I probably do. You can cut through the stems and the roots, and they look different, so it's pretty easy. What I love is I thought, I wonder if we'll be able to fill 43 minutes with this. I'm wondering if we'll even get the potato out of the ground.

8:27I mean, did you... Well, out of the egg box. Also, the roots have very specific functions. You know, they absorb all the nutrients and the water. out of the soil, whereas the Stolons don't really do that, although they do have small roots of their own, so the Stolons will form little small roots. This is complicated. It is quite complicated. You thought physics was hard. Well, no, you didn't, but I did. The first question we had written down here, we should get to the first question. No, let's not worry about things like that. I want to know from you, because you said 30 years, you know, you've been studying genetics and potato, and when you first started that, did you think you would be doing it for three decades?

9:04I mean, what was your, when you first approached the subject? Well, I'd worked on wheat for a while, a place called the John Innes Centre in Norwich, and I'd heard that there was going to be a permanent position coming up in Scotland to do genetics on crops. And then when I saw that it was a potato job, I was kind of crestfallen. A potato job? Potato genetics is notoriously complicated because cultivated potato, the potatoes we buy are tetraploids, so they have four sets of chromosomes. instead of two like we do. Now we have two of each chromosome and potatoes have four. And that makes doing genetics very complicated.

9:42Breeding is much more complicated for potatoes. So it takes longer to breed a new potato variety than it does to breed, say, a variety of wheat or rice. Is that uncommon to have the four sets of chromosomes? It's not that uncommon, no. I mean, you tend to get bigger, more vigorous plants when they're polyploid, but it does make the genetics much more complicated. So, no, I didn't think I'd be doing it for 30 years because I thought, you know, I'm going to do this for a few years and see how it goes. But then it just got... It's kind of a vocation working on potatoes. Well, they draw you in, the potatoes.

10:13It draws you in, yeah, and it's very interesting and the history of potatoes is very interesting and it's a real challenge to do potato genetics. And also the advances in the last sort of 15 years in genomics, you know, sequencing and all that sort of thing, has actually made the genetics much easier than it used to be. so it's possible to do things now that you could not think about doing 20 years ago. Before I ask what those things are, Sandy, you wanted to come in on that? I think we think of potatoes as being quite variable, right? There's red ones and white ones and little pink fir apples and stuff.

10:47But those are all the same species. Those are all the species that's called Selenum tuberosum. They're the common cultivated potato. But there are 104 wild species of potatoes which grow in the Andes. so the diversity of potatoes is is enormous and it's it's exciting and that and that's the kind of potato work that i do is collecting things in the field and looking at at wild species and they do their tubers in lots of different ways they have some of them are like little pearls on a string there are all kinds of variations so when we think of the potatoes that most of us would be eating you know what percentage of that you know if we go to the supermarket and there's normally what i I don't know, six, seven, eight different kind of forms of potato to buy sometimes.

11:28How much of that is a percentage in terms of representative of? It's one species. Just one species? One of 104. In the Andes, there's three other potatoes which are cultivated. They're cultivated way high up in very high elevations, and they're used to make freeze-dried potatoes, which are called chunyo. What you do to make chunyo is you put straw on the ground. You can do this at home. You put straw on the ground. You leave the potatoes out overnight. They freeze. And then the next morning, you tread on them and make all the water come out. And you do that several nights in a row. And you end up with chunho, which looks like this.

12:05And is it right you said they're disgusting? They're not. Well, they're not. They're an acquired taste, Robin. Right. It looks like a pebble to me. The chunho looks like little brown pebbles. And that you use in stews and stuff. And then this white one. This is a white one, which looks like a bit of chalk. It's called Tunta, and it's made in Bolivia, and they basically just wipe the skin off. But it's very light. It's like a piece of styrofoam. Do you want to try one? Yeah. OK, here, you can have this one, Robin. Here we go. I'd love to try some. What's going to happen when... Well, we'll find out.

12:38You're going to get polyploidal before you know it. I mean, there's been a lot of discussion about chromosomes and genetic stuff, so I'm just slightly concerned as to... It's very, very difficult and incredibly hard, Susan. It's very hard. Yeah, it's very hard. It's potato. It's not that dissimilar to Edinburgh Rock, if Edinburgh Rock wasn't made of anything. Don't you start rubbing it. So the thing is that you're supposed to cook it. Oh, right. Well, we look like a couple of fools now. It's fascinating. Yeah, you're right. As you said, the kind of polystarring quality, the kind of, you know, again, literally everything that we think of in terms of the moisture of, you know, when you have a lovely baked potato or mashed potato, this is like removing everything.

13:22Because that's the other thing. Now that we've got this weird thing, can you explain something to me, which is why, when we used to have mashed potato at school, was it hairy? That's about the cooking of the potato, because I want... Because there's the starchiness of the potato, which is part of the joy, yet part of the danger. My wife is very much into the soup in the house. I don't know if you've got a similar thing. She does the soup. I don't do the soup, because I can't do the soup. Soup, whilst a simple thing, can be easily ruined. but for some reason, I don't know what had happened to me I thought, I'll do the soup you know, when you get to a certain age, you just lose your mind a bit so I thought, I'll make potato and leek soup which I don't know where that came from because I don't like it but you like potatoes you like potatoes I like potatoes, that's the thing, because I love potatoes I thought, well I'll make potato and leek soup because the point of potatoes, the reason I love potatoes is they're omnipresent and they fill you up and they're cheap and they're affordable and they're brilliant and as far back as I can remember potatoes were with every single meal and when I was at university I lived on an entirely potato based diet so I made this potato and leek soup I mean you could have papered the house with it it was the most disgusting and I remember my better half sitting there you know that way you have to go mmm this is lovely you've got to make it with the right kind of potatoes so they kind of come in two sorts I thought you said they were all the same potatoes they are all the same they are all the same They're all the same species.

14:51But what people do to their crops is we modify them. This was the kind of whole point of Charles Darwin's Origin of Species. He started out with how people modify domesticated animals. And what we do is we change them to suit our purposes. And so in the Andes, I mean, we have maybe six or eight. Well, actually, my supermarket only has four kinds of potatoes. but in the Andes I once met a man who had a rug about the size that this is in front of us, so maybe kind of three meters by three meters, and he and his wife had more than a thousand different kinds of potatoes on this rug, and I asked him what they were called, and he started reeling off names, you know, this one and this one and this one, and they all had a different name, and they all have different uses, so there's potatoes to make soup with, there's potatoes to make chunho and tunta out of there's potatoes to roast there's potatoes and it kind of depends on whether they're starchy you know like it was a very starchy potato sort of the ones that kind of explode when you roast them and you put a knife in them and they go or there's the waxy ones which turn into kind of wallpaper paste if you try to make soup that might have been what happened you get very high dry matter potatoes which are you know have a lot of starch and they're used for more for like baking and roasting and then you get your salad potatoes and they tend to have a particular type of starch called amylopectin.

16:13So the salad potatoes have more water in them and less starch overall, but the starch tends to be a starch called amylopectin, whereas the other ones have amylopectin and amylose. So what is the history? So you mentioned the Andes. So these are native to South America. They're native to South America, and there's the great myth that Walter Raleigh brought the potato to England, which is, of course, totally false. It was the Spanish. But what was amazing is potatoes, when they first came to Europe, didn't tuberise properly. Because in the Andes, where it's near the equator, the days and the nights are the same length all year long.

16:48Whereas here in the Northern Hemisphere, we have very long days in the summer and very short days in the winter. And potatoes don't tuberise well in long days. So the very first drawings of potatoes from Europe had these little teeny-weeny tubers. They looked pathetic. little pea-shaped things. And very soon after coming to Europe, a mutation occurred that allowed them to tuberise in our long-day growing environment. As you described it, so you said that there were hundreds of different potatoes in this village that you found and this couple selling them. So does that imply that there's quite a sophisticated cuisine around them?

17:27Very sophisticated. An incredibly sophisticated knowledge of the different varieties of potatoes and what you use them for and how to propagate them and what climates to grow them in. Potato agriculture is very, very sophisticated in the Andes. And one of the sad things is that a lot of times, which is true with indigenous crops, is that as mechanized agriculture comes and improved crop varieties come, the indigenous varieties, which are perhaps not as disease-resistant or don't have as high a yield, they disappear. And it's like a species disappearing. It's like a language disappearing. It's part of the culture disappearing.

18:04And they're incredible names as well, very descriptive names of potatoes in the Andes. My favorite one is called Kakchun Wataki, and it means potato that makes the young bride weep. And basically, this potato looks like a grenade, you know a grenade, but with really big bubbles on it. And so your test before you got married was you were supposed to peel the potato without wasting anything. so I would have never ended up married in the Andes because I would have just cut all those bottles off this is genuinely mind-blowing because potatoes have been such a part of my life for such a long period of time and I had no idea any of the things that you were saying to me either of you regarding the species how many of them there were it's in a way I take them for I think we take them for granted because they are so important and they're always there.

19:03I actually become quite upset if there aren't potatoes in the house because, you know, when you've got a potato in the house, you know you can always have something to eat. If there's a potato in the house, you can always eat something with it because they're just so important to us. But when you talk about it, it's really quite poignant talking about losing a species of the potato is like losing a language. But sitting and going to a supermarket in Glasgow, I don't even know anything about this. It's been, this is, when you said come and talk about potatoes, I thought, well, all right then. But this is completely unexpected.

19:38They are wonderful. They are wonderful. People in the supermarket in Glasgow who go, I can't get the potatoes. There's some bloody woman who won't get out of the way. And she's just talking and talking about them. Sorry, before you buy those potatoes, yes. And it's wonderful. And you do see variety. So next time you go to the supermarket, have a look at all those different ones. Sorry, I don't mean to, pardon me. So when I go to the supermarket and I'm in front of the potato section... Speak to them.

20:07Tell me what I should be... Because I want to appreciate the potatoes now. This is changing me as a person. And I want to go to my local supermarket and I want to appreciate them. How do I appreciate a potato more than I'm currently appreciating potatoes? Well, think about the difference in the colour of the skin and the colour of the flesh and the deepness of the eyes. and there's a wonderful thing in London. Sounds quite romantic. It is romantic. But there's a wonderful thing. On the third Sunday in January, there's a South London potato fair and potato fanciers from all over the south of England come and exchange potato varieties and you can get some really interesting potatoes.

20:47Ones that cook blue or purple, ones that cook bright red. They're fantastic. I'm just wondering about becoming a potato fancier at my time of life. I think it's probably right. Many of those interesting coloured ones come from Scotland. You know, there's things like Shetland Blue and Congo. I've used a blue potato before. There were quite a few varieties that were bred in Scotland that had these nice colours. So can we, as you can with an animal, for example, can we trace the genetics back? Can we see from what the species, the initial species was from which all this diversity emerged? We published some work some years ago using molecular data showing that the main domestication event happened about 8 ,000 to 10 ,000 years ago somewhere near Lake Titicaca, southern Peru, northern Bolivia.

21:32But that's been challenged quite a few times by other people. And there was originally a group of species, about 30 species, the Brevicali group, which I think has been collapsed down now to just a couple. So the idea was it was domesticated from that group of wild species. They're related to the nightshade. So the indigenous species here related to them? They are related. They're like distant cousins. So we don't have any native potatoes, although there are lots of kinds of potatoes in Scotland. But we have no native potatoes in Europe. The only native potatoes are found from the southern United States down through Mexico into the Andes, into Brazil.

22:12So they're only in the Americas. So what is this relationship to things like the nightshade family, which you find here? When did that split away? Are we talking about hundreds of thousands of years ago? Millions of years. So 20 million, maybe. But now we're revising all those dates because we've just submitted. So everybody cross your fingers that this paper will get accepted. We're just describing a whole bunch of new seed fossils of Solanum, of Solanaceae, of nightshades, which are from various parts of Europe and also from the United States. Seed fossils. I've never thought of seed fossils really before.

22:45Well, you get... I mean, they're quite hard seeds, really, and they fossilise quite well. So we're revising the dates of when all of this happened. Watch that space. So we could have a kind of Jurassic Park that's more potato-based eventually, kind of... We could. We could, but the interesting thing is that the nightshades, the genus to which the potato belongs, the plants don't all look like potatoes. They're extraordinarily different. There are huge spiny trees and tiny plants about this big that grow way high up in the Andes. So they're hugely diverse. Potatoes are just one part of the family tree.

23:22I always get the terminology wrong. Is it the genus? What is the... Solanum. Or solanum. It comes from, well, nobody knows where it comes from. But we can make it up. I've made it up many times. That's fantastic. The way that you very confidently went, it comes from... No, no one knows. That's... Solanum. But then why do we end up, though, as you keep saying, about the fact that we've only got one species? Because it's the cultivated one. I mean, at one point there were more cultivated species, but they've been reduced in number to four now. So would we have seen, if we went back even a few hundred years, would we have seen that some of the potatoes that were coming over here, some of the potatoes that were being eaten, some of the potatoes that were...

24:02Or we basically were still talking about that one species? No, that one species is the one that was brought to Europe. Can I just ask a question? Again, I'm in the supermarket. You're saying that there is one species of potato. Yep. But they're all called different things because you've got your Marist Pipers and you've got all the other ones. They're different varieties. Right. Or cultivars. So they've been bred by breeders and then they get a name. People made them. They become a variety. But they're the same species? Yeah. So genetically, they're all the same. Kind of. I mean, we're genetically not all the same, right?

24:43And we're all the same species. So it's like dogs, really. Yeah. I think potatoes and humans in some ways are quite similar because... This is when there's going to be a twist now. Twisting the show. No, because most crops, like seed crops, are inbreeders. Like wheat, rice, barley, these crops, they're what we call homozygous genetically. So if you grow a wheat plant and click the Cs and grow them up, they'll all be the same as the plant that you got them from. If you take a potato plant, in fact, that's how early potato breeding worked because they didn't have the ability to cross one variety with another the way that normal breeding works.

25:19They just collected seeds from a potato plant and because it's highly heterozygous and tetraploid, all the seeds are completely different from the original plant that you got them from. And then what they would do is they'd grow them up and see what the tubers look like and said, oh, this one looks nice, we'll call this Victoria. There was one called Patterson's Victoria in Scotland, and we liked the look of this particular tuber, and then that became a variety. But then from that point on, if you want to keep that variety, you have to grow it as tubers. You can't propagate it via seed. You have to propagate it vegetatively, which makes what Sandy said about all these hundreds of varieties in South America so amazing, because they have been propagated as tubers for hundreds or even thousands of years.

26:05And as soon as you lose one, it's gone, you know, because it's genetically unique. So genetically, there's so much diversity there. It's definitely didn't help. If you grow them by pollination, then what you get is not predictable, right? You're shuffling the deck every time. And it's a big deck in this case. It's a big deck, yeah, a very big deck. So potatoes are like humans. No, no, I didn't really mean that. No, I'm still trying to... I'm not being facetious at all. I'm still trying to understand this. I'm so sorry. You asked me to come on. No, I love this. I thought... My whole life's been a lie.