This week we dig into into the science of farming and food production. We find out how transgenic plants can help us dispense with the need for chemical pesticides and how giant greenhouses at the shoreline can be home to super-efficient farms of their own. We explore the problems faced by our sweet honey bee and in Kitchen Science we do some plant modification of our own no transgenics knowledge needed, just food colouring...
In this episode
30:19 - Transgenic Plants
with Professor Jonathan Jones, The Sainsbury Laboratory, Norwich
Chris - Now, one of the things that farmers have to do is to combat the problem of plant pests. And at the moment, they tend to do that in one way which is by using chemicals to treat the problem. But one alternative could be the use of genetic techniques. In other words, we could take genes from one plant or perhaps even a totally different species that knows how to destroy a pathogen, give it to a plant and that plant then has the ability to ward off that pathogen chemically, but without farm having to add additional chemicals. How do we do this and why is it any better than existing techniques? To tell us, here's Professor Jonathan Jones, he's based at the Sainsbury Laboratory in Norwich. Hi, Jonathan.
Jonathan - Hello there.
Chris - And welcome to the Naked Scientists. First of all, if you would, just tell us, how do you actually make a genetically modified plant?
Jonathan - Well, a plant carries 50,000 genes or so, and the idea was to put in a gene or two that confers a useful new trait. And to do that, you take advantage of a bacterium called agri-bacterium which naturally causes galls on a number of crops, particularly grapevine but a number of others too. And it does this by introducing DNA into the cells of that plant, that make the plant more conducive to the growth of bacterium. And what scientists have done over the last 30 years actually, is to understand this process, break it down into components, and then use their knowledge of the DNA that transfers the DNA into the plant cell and get rid of the genes that make the plant cell do a number of growth characteristics that are not good for the plant. And then you can put in genes that confer properties that would be advantageous for the crop and then what you do, is you incubate the plant cells with the bacteria and then you select for those plant cells that receive the genes that you're interested in and then at the end, you get a plant back from that, that has 50,000 genes it started with and has a couple of new genes as well.
Chris - What sorts of things have scientists done, in terms of actually making functional crops that will be useful? What sorts of genes have they inserted to enable crops to do novel things?
Jonathan - The first thing that was done was to help farmers control weeds. And so, in the absence of weed control, you can lose 30% or 40% of your yield. I can go into my back garden and do some hoeing to control weeds, but they're constant problem, as anyone who has ever grown any crops or allotment will know. And if you go out in a 50 hectare field or whatever to control weeds, then there's no alternative really to herbicides. And the problem is that many herbicides are damaging to water courses, they're quite persistent. And so, the herbicides that were being used a lot in the '70s. there's a strong incentive to replace them with something that was less persistent. And the main one that was adopted worldwide was the glyphosate resistance trait. So, glyphosate is a very good herbicide but it kills all known plants including the crop. And so, what was done was to engineer in a gene that meant that the crop survived the glyphosate and so, the weeds were better controlled. And glyphosate is inactivated quickly in the soil so, it's less damaging way to control weeds than methods that it replaced. Subsequent to that, then there was an insect control. So there were proteins that are toxic to larvae of moths and butterflies such as the boll weevil, such as the corn rootworm, such as corn stem and cob worm. And so, you can engineer the plant to make a protein that kills the insect and that's better than the technology it replaced which was applying insecticides.
Chris - Can I ask just you something about the practice of making a genetically modified plant because...
Jonathan - Yes.
Chris - ...when you actually put the foreign gene from one organism or one plant species into another to give it that resistance, do you know where into the plant's genetic material that had integration, that insertion has occurred or is it to all intents and purposes random?
onathan - Where it goes in any particular transformation event is currently unpredictable but you can then find out were it went. Because what's actually done to bring some of the commercial variety is to make hundreds of transformation events or even thousands and select one that has no, shall we say, collateral damage in terms of the performance of the plant and then characterize where it went in very thoroughly. So, anything that's on the market is very well defined, where the gene went in. There are new technologies becoming available to put DNA in at a defined position and currently, that's experimental but it looks promising. But no crops resulting from that technology are yet anywhere near commercialization.
Chris - Because if I might ask you very briefly, just to give us the answer to this, which is that, if you got to say, a gene in a plant which is not essential for that plant to grow, but it does for instance remove a toxin that might be bad for us if we ate the plant, but it doesn't really harm the plant, if you put your new gene into the plant and it deactivated that gene that gets rid of that toxin or it makes the plant, so it's more vulnerable to something else, it might grow a mold which is bad for us if we eat it. How do we know that hasn't happen and that therefore, we haven't had some kind of knock-on effect to the safety of the crop?
Jonathan - Well, when I said that there's a lot of transformants was made in any such experiment which then screened for their properties or whether there's any collateral damage, that's the kind of collateral damage that people look for. There'll be experimental acres, you know, large area devoted to this trialed crop before it hits the public and if anything like that would happen, it would become clear at an early stage before it reached the market.
Chris - And we will be talking about organic farming in just a second. Why is this better than organic techniques?
Jonathan - I mean, the problem with organic farming is that yields are low. Lower than conventional agriculture. It is true that they cause less collateral damage, there's less risk of nitrogen run off into water courses, there is certainly no insecticides applied, although that you use copper sulfate to control late blight in potatoes. But the main problem is yield. By 2030, we're going to need to double yield because of the growing population and because of increasing demand throughout the world for more meat in the diet. And to double yield it is going to be tough ask and I don't think it is going to happen with organic agriculture.
Chris - So basically, we need the technology that you're coming out with.
38:16 - Biodynamic pest control on organic farms
Biodynamic pest control on organic farms
with Professor Jane Memmott, University of Bristol
Helen - Organic farming may not necessarily produce the yield we need to feed the world in future years, but it is booming business, it's increasingly popular and they go about - organic farms go about dealing with the same pest that conventional farmers face but in a different way. We sent Ben Valsler let meet Professor Jane Memmott at Bristol University to find out more.
Ben - How do organic farms deal with pests? Conventional farmers use pesticides to kill them off, but organic farming relies on the natural predators present acting as bio-control agents to kill off the pests. This is known as Biodynamic pest control, and it's a major part of organic farming, which limits or excludes both pesticides and synthetic fertilizers, with the grand aim of improve the health of soils and ecosystems. Biodynamic pest control relies on having high biodiversity - a wide variety of plants, insects and animals in the ecosystem.
To see if biodynamic pest control really works, Professor Jane Memmot at the University of Bristol, found 40 farms to compare - 20 organic and 20 conventional. To get a real understanding of what's going on, Professor Memmott's team were looking at the useful roles that organisms play, such as pollination or pest control, also known as 'Ecosystem services'...
Jane - We wanted to look at the scale of the whole farm, and we also wanted to look at interactions between species, because ecosystem services, all of them, are about interaction between species. Whether it's a caterpillar pest and its bio-control agent, whether it's between a flower and a bee that leads to an apple or a tomato or whatever, they all involve interactions. So rather than just counting species, which is what previous studies have done; they count how many birds or how many beetles or how many spiders are on organic and conventional farms and compare the two, we wanted to put together food webs.
Ben - In an ambitious project, Jane and Bristol University undergraduates set about mapping and sampling all 40 farms -observing all of the plants, predators, prey and pest species present. They payed particular attention to parasitoids - organisms which spend a portion of their life parasitizing another. As gruesome as this sounds, parasitoids that target caterpillars are essential to pest control...
Jane - So every month a team of people would go through the farm and sample transects in each of the different habitats. To do that you walk through or go through on your hands and knees, through the habitat, and you're collecting all the caterpillars and all the leaf miners in that habitat, and you're counting all the plants that are in that habitat. You then take your caterpillars back to the lab and you either get a moth or you get a parasitoid out of them. So that information can then be used to join up all of the species into food webs; who eats who, which caterpillars eat which plants and which parasitoids eat which caterpillars. And we've got one of those for each farm.
Ben - The food webs predictably showed that there was slightly more biodiversity on the organic farms than on conventional farms, but food webs alone cannot tell you how effective an ecosystem is at tackling pests...
Jane - So what our prediction was next was that the organic farms would provide better biological pest control. You've got more species of parasitoid on there, more semi-natural habitat, so they should give you better pest control. Indeed, the whole ethos of organic farming is that one of the reasons they don't get as many pests is because they've got all these beneficial insects that eat all the pests.
So what we did next - it's actually my favourite bit, it's the clever bit - was that having got the networks we then decided to manipulate them in some way. Now what we wanted to do, the ideal experiment, is to find a pest, a new pest, and put it on all farms and see if they're better controlled on the organic farms. But you can straight away see that that's not going to work. It's ethically, morally suspect, you just can't do it - the farmers would never let you back again! So you can't do that so what we did instead was we found a surrogate pest, we found something that was pest like but would not appear on the farms naturally, and we could use as a kind of surrogate pest to ask what would happen if a new species of insect came in. And the particular insect we used was a thing called the Pyracantha leaf miner.
Ben - As its name suggests, the pyracantha leaf miner is a pest that lives inside the leaves of the pyracantha plant - a hardy, prickly plant that wouldn't normally be found on a farm. By planting 40 pyracantha bushed on each farm and introducing the leaf miners, they can act as a surrogate pest to show the level of natural pest control.
Jane - And what we found really surprised us, because we found that for this particular species, the pest control was no better on the organic farms than on the conventional farms. So there was no difference whatsoever in the number of them killed. So this kind of made us scratch our heads a bit. And what we did then was, because we have these networks for each farm, we went back to our networks and asked, well, how many parasitoids are there that would probably attack this species? And actually it turns out that when you retrospectively predict what could attack it, there really aren't more species of parasitoid on organic farms than conventional farms.
Ben - Using the same data, they were able to predict that just three of more than thirty families of insects would be better controlled on the organic farms - Professor Memmott now plans to introduce surrogate pests from each of these families, and see if biodynamic pest control really does work.
So what does this mean for organic farming?
Jane - The conventional farms all have lots of semi-natural habitat on them, so they are kind of getting this pest control for free and they don't necessarily realise that it's there. So it's not just having more biodiversity, it's actually having the right sort of biodiversity that's really important. Conventional farms can actually get an awful lot of the biodiversity gains of organic farms without going wholesale organic. We're never going to have more than about 5-10% or farms organic in the UK, I don't think, ever, so that 90% of other farms, if they can make small changes in what they do that could actually have a really big effect on biodiversity nationwide. And if they can take some of the things that really work from the organic farms which don't involve wholesale conversion to organic-ness, then that could reap huge biodiversity gains across the country.
Ben - So adopting certain aspects of organic farms - for example growing healthy hedgerows and areas of semi-natural habitat, or reducing reliance on pesticides - could see conventional farms bursting with biodiversity, and naturally protected from pests.
Jane - But little changes from the great majority of conventional farmers, rather than having another 2% of organic farms say, could make the most enormous difference.
Chris - So you don't need to be totally organic. Just a bit organic would do. That was Professor Jane Memmott, she's at the University of Bristol and she was talking to our own Ben Valsler.
44:26 - Seawater Greenhouses
with Charlie Paton, Seawater Greenhouse Ltd
Helen - It doesn't matter how you grow your crops, whether they're organic and it doesn't matter on how you're going about, trying to deal with pests. There's one thing that crops will always need and that is water. Well we're now joined by Charlie Paton and he's the Managing Director of a company called Seawater Greenhouse and the name might be a bit of a give away but we're going to find out from him, all about what he's been up to.Hi, Charlie! Thanks for joining us.
Charlie - Yes, hello.
Helen - First of all, could you describe what this Seawater Greenhouses are and what's the problem you're hoping to solve with and why do we need them?
Charlie - Okay. The greenhouse is - most people think of greenhouses as hot houses. Well these are cool houses because we cool them with sea water. So they're designed for hot Arab climates like North Africa and the Middle East and Australia, and we cool them by using sea water which we pour over a kind of construction which is a honeycomb cardboard material which is a cross between a honeycomb and if you like, a sponge. So we have a very large surface area of wall that is wetted with sea water. Now, when the air comes through that, it's cooled and the humidity goes up. So, by cooling the air and raising the humidity, we create conditions that plants will grow in, when they wouldn't have otherwise.
Helen - So, you want to grow plants in the middle of the desert where really, they just wouldn't grow normally because it's hot, too dry, there's not enough water.
Charlie - Exactly.
Helen - So you're cooling things down and you're creating water as well.
Charlie - And we're creating water as well because at the back end of the greenhouse, we have another arrangement with a similar evaporator but this time, we put hot water, hot sea water over the back evaporator before the air goes out of the greenhouse. And then it passes through a small heat exchanger which is cooled by the water that we cooled on the front wall. So, it's rather like having a hot shower and seeing water condense on bathroom mirror.
Helen - Right. Now, do these things have to be built near the sea? And then also, what do you do with the salt once you get rid of it, when you've produced this fresh water? Presumably, you have a very strong brine left over at the end. What do you do with that?
Charlie - At the moment, we put the salt back into the sea water, but our intention is, in the future to separate out the various minerals and indeed, use it a lot of them for the plants themselves.
Helen - So, you can use that as well to help grow the plants but the plants do need those salts but in different quantities and different amounts?
Charlie - Well, exactly. If you can, in simple terms, if you can take the salt that is a sodium chloride out of sea water, you've got a very good, babybio type mixture which has got all the trace elements and a lot of the nutrients that the plants need. And in fact, seaweeds and fish meal are perhaps the best fertilizers you can get.
Helen - Now, does this need any electricity because I believe, one of the big problems with using desalination plants, is they're really energy hungry. You have to use a lot of energy to create that fresh water. Are you using any electricity at all in you're greenhouses?
Charlie - Yes, we are. It's a very small amount of electricity and it's extremely efficient. We use, typically, if I can put this in perspective, we need power for the pumps and the fans which regulate the airflow and typically, we use around two kilowatts of electricity to remove about a megawatt of heat.
Helen - So that's good, is it?
Charlie - It's very efficient.
Helen - Excellent. And in terms of the efficiency of what you're growing and say, how big a greenhouse would you need to feed a family or maybe a village, if you like?
Charlie - Oh, there is no limit. I mean, greenhouses are made in a modular sort of way and there's no limit to the scale. I mean, at the moment in Europe, we get a lot fresh of our fresh produce from greenhouses and those in the South of Spain for example, there was 40,000 hectares of greenhouses, primarily producing out-of-season crops for us in Europe in the winter months.
Helen - So, would this work in countries like Britain or are you really aiming at those very dry, arid countries?
Charlie - No. It's aimed at places like North Africa, the Middle East, Australia, India, and those sort of places.
Helen - I believe you've got a project, is that right? Called the Sahara Forest project. What's that about?
Charlie - That's right. We've sort of taken it one step further and I'm not sure if you're familiar with concentrated solar power. But it's a process that's getting more and more interesting and people getting more excited about. Where you very simply have an array of mirrors in a hot sunny place and the mirrors are focused onto something that heats up water and you turn that water to steam and you use that steam to drive a steam turbine. And there are various different versions of them, but several have been built and there were quite a lot being planned. And there's some fairly grand schemes for Europe to actually source its electricity from the Sahara through these systems. Now, our thinking is that as with any thermal process that makes electricity, there's a lot of heat to be got rid of. And that if we have that sea water greenhouses in the vicinity of these power plants, we can take that waste low grade heat and use it to evaporate and condense a lot more water.
Helen - Thanks Charlie, that was Charlie Paton, he's the Managing Director of Seawater Greenhouse - they're developing an elegant system to both grow crops and supply freshwater to arid areas!
Why is the demand for meat increasing?
We put this question to Professor Jonathan Jones:Well, many would say, quite reasonably, that we shouldn't increase the meat demand, but the fact is that we will. It's clear that China's appetite for meat in their diet in particular is going up and up. These are people who, from having rice seven days a week, now want have rice plus meat in one day out of seven and maybe even two days out of seven. And so, as affluence goes up, demand for meat will go up, and I think it's unfortunate because we could reduce our impact on the environment if we ate less meat, especially in the West. But anyway, I think that's what's going to happen and a major trade pipeline is soy beans from Brazil to China to grow pigs.And to Charlie Paton:It must be in everybody's interest to eat less meat and therefore, it must be in everybody's interest to have greater biodiversity of fresh produce and that is one of the things we're very interested in, in encouraging.
Could we collect steam from power plants as fresh water?
We put this question to Charlie Paton:Well that's essentially what we're talking about [with Sea Water Greenhouse]. Yes. Exactly, that's the same thing.
Are fast-growing GM plants weaker?
We put this question to Professor Jonathan Jones:Well usually, they don't grow a lot faster. They're just more disease resistant. So you'll have less losses. So if your roots aren't eaten by corn rootworm for example, they're actually stronger because they can take in more water. The roots are not removed from the equation, so the water harvesting from the soil. Both for the plant, is more efficient.
52:15 - Could I inject DNA from one plant into another to make a new fruit?
Could I inject DNA from one plant into another to make a new fruit?
We put this question to Professor Jonathan Jones:What distinguishes one fruit from another, involves more than one gene. It's pretty complicated. If you want to convert white grapes to red grapes, then the gene that distinguishes them is defined. You could put that gene and get a red grape back, but you couldn't change species with one gene.
When will seawater greenhouses be available?
We put this question to Charlie Paton:Well, we've built three and we've got three demonstrators working in different parts of the world and we are planning a fairly large scale commercial operation in Australia which will happen some time, I hope, later next year and we're working quite intensively on the Sahara forest idea. We don't know where we're going to start but we're putting the numbers together.
Will seawater greenhouses be affordable?
We put this question to Charlie Paton:Well, it's a method of creating wealth in a sense because if you have no water, you can't do anything. If you have water, you can create jobs, you can create food, and you can create energy.
Why does it smell so nice after it rains?
The answer to this was quite slow coming and no one really knew for sure, perhaps we still don't know for certain, but there was certainly some work done on this in the 1960s and the paper got published in 1966 where scientists actually, they think got the answer. The theories where that this could either be something coming out of the soil, something reacting with water in the soil to produce the smell, or perhaps something organic, something living and it turns out, it's probably the latter. A group of scientists analyzed the air and they found that when you took soil, you find a very common soil bacterium called actinomycetes. This is a filamentous bacteria and it grows lots of little filaments that ramify through the soil, picking up nutrients. But it also has another form which it uses to protect itself when the soil is very, very dry. So, when there's severe arid, dry conditions, it recedes into a spore and this is a dormant form of the bacterium from which it can reactivate when water comes back and the soil is fresh and there's lots of good environment for it to exploit again. So what scientists think happens when you get a rain shower and it produces that beautiful earthly smell in the air, is that the rain comes down, it hits dry soil where all these bacteria have formed this little spores, the spores then get ejected up into the air, and they drift around in a cloud. Because they're so tiny, they stay drifting around in the cloud for quite sometime. You then breathe them in and they smell the way they smell. That's their smell. But it's also a form of, sort of, dispersal for the bacterium because it then descends on another patch of ground, out of the air and can germinate and grow. So, I suppose that's one point. Another thing to bare in mind is of course, there's the other possibility that was also raised by scientists historically and that is that there are various chemical reactions that can occur when water hits soil or dry soil or a rock. And so, it might be that some of these smells, because of particular rocks getting wetted, then chemical reactions are being elaborated and then they produce various chemicals that go up in to the air. But we think it's mainly the actinomycetes, that's the main cause.
56:06 - Why do washing powders remove stains but not dyes?
Why do washing powders remove stains but not dyes?
So an answer to the first part; one of the main and important ingredients used is surfactants and the surfactant molecule is clever in the way that on one side it has a hydrophobic component, that's a water-hating molecular chain. And on the other side, a hydrophilic water-loving component. The hydrophobic chain finds itself sticking to the stains on your clothes and the hydrophilic heads have a stronger attraction to water. They're able to surround the dirts and roll it up into a small globular-type ball and the end result is that they're able to lift the stain from your cloth, into the wash water. Some of our detergents contain enzymes which are naturally derived molecules. Generally, we use different enzymes such proteases which break down proteins and amylase which breaks down starch and then finally, another major ingredient that we use, like most other detergent manufacturers is bleach. The bleach turns the stain into more soluble colourless particles that can be easily removed and carried away into the wash water. So, in actual fact, it can remove bleachable dye stains. So, to kind of answer the other part of the question, laundry detergents can remove certain dyes, as well as stains.Most dyes are composed of molecules that these ingredients can't target. Surfactants can't globuralize the dyes, nor can enzymes gobble them up, unless they're vegetable-based. But bleach can effect dyes and this is why, washing powders designed for colored clothes don't contain any bleach.