HIGH FLYERS THINK TANK

Biotechnology and the future of Australian agriculture

The Shine Dome, Canberra, 26 July 2005

Biotechnology: Horticulture
by Dr Steve Swain, Senior Research Scientist, CSIRO Plant Industries, Victoria

I am going to talk about how biotechnology in terms of horticulture relates to Australian horticultural production, some reference to other things in the rest of the world.

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I can't really talk about horticultural biotechnology without mentioning the famous flavr-savr tomato, which was originally released in the US in 1994. It relates to what Craig Cormick was saying, in fact. This came out and was actually quite successful and well accepted, and there were no controversies at all, but it did precede some of those issues about the publicity and anti-GM type things that arose a bit later.

To turn more to what is in Australia: one example is disease resistance, in terms of papaya resistance to ringspot virus. (There is some other work being done in Australia on papaya, which is a tropical crop.) This is one of the major horticultural crops out there in the world and I think more than 50 per cent of the production in Hawaii, which is the major producing place in the US, now has GM papaya for disease resistance.

The other thing I want to point out here which has not been commercialised, as far as I know, is research into secondary metabolism. That is illustrated by vegetables with cancer-fighting compounds. The reason I want to point that out is that these allow me to illustrate some of the differences in the sorts of crops that can be produced, and also relate to some of those points Craig was making about the different sorts of crops and how that might relate to acceptance.

So, in terms of the disease-resistant type things, this is really one of those products which are of no real, direct benefit, obviously, to the consumer – or it is not obvious to the consumer what the benefit is. This is to benefit production of papaya, whereas the secondary metabolism is something I know some of the biotechnology companies in the United States are thinking about, and the real aim here – whether or not it will be successful, I don't know – is to use this as a way of selling GM products. The idea would be that they might advertise that these are in fact GM vegetables, but GM vegetables with compounds that will make you stay healthier or to fight off various diseases.

I think the biotech companies are seeing this as a major way to go for the future, but as to whether that becomes successful in places like Europe is not so clear.

One of the main points I want to make here, though, is that in terms of what is going on in Australia, in horticultural crops, most work aims to improve quality traits rather than production traits. I think that is important, for a couple of reasons. One is that it is quite often said that one of the problems with biotechnology introduction, or GM crop introduction, was that the initial traits that are out there now largely focused on input-type traits.

[inaudible] about product differentiation than it is about quality, there is less focus on input traits as compared to field crops. So, because the quality in appearance and taste, et cetera is so important, to some extent horticulture has tried to jump over that first wave of input traits and moved on to the quality traits. But because it is generally more difficult and slower than in field crops, it is still lagging behind.

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I am just going to go through a few examples of horticultural crops, particularly focusing on Australia, and biotechnology/GM crops. The most famous example is the GM carnations. If you read Ian Edwards' slide carefully, you might have seen that it was 'flour' colour that was the target – but in fact it is not flour that you make from carnations to eat; it is the colour of the actual flowers!

This is a more purply-mauve carnation, which is commercially available in Australia and has been for about a decade now. The reason these colours have been modified is a change in the compounds called flavonoids. These are compounds which give rise to many of the different colours, the reddy-blue colours, that you see in horticultural crops and other vegetables. These compounds control colour, which is important for appeal, and they also control health benefits. So I don't think anyone has actually advertised it, but I guess theoretically if you ate these carnations they might have some beneficial effects for you. But no-one is actually suggesting that.

That really makes a more serious point, however. I think a large part of the reason that you probably haven't heard about these GM carnations in the news, and they haven't been very controversial, is that they are not a food crop. Nobody does eat them, so it has not become such an issue and they seem to have largely gone under the radar.

Appearance is obviously a quality trait – it has got nothing to do with production but is all about getting consumers to buy the actual product. This second example of appearance is the blue rose. I thought I might mention this because I think it is close to commercialisation, at least in some parts of the world.

The carnation was developed by an Australian company called Florigene, which has now been merged. But now they have also, I think, achieved the famous blue rose, which people have been trying to achieve for decades. In fact, I mentioned this to my mother a few years ago and she said that 50 years ago she worked on the blue rose. I thought that was pretty advanced, but apparently what they used to do then was to take white roses and dip them in blue ink to make them blue. With several millions of dollars worth of research, we can now potentially do it without the blue ink.

In the first phase, the Florigene company took the gene which gives you the blue pigment and added it to roses. (The reason you can't breed blue roses through conventional means is that they don't have this blue gene.) But the roses were still making the red pigment, so you got a mixture of red and blue, and hence purple.

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But more recently, using some of CSIRO's technology, they have used a technique called RNAi – which many of you would be familiar with – to turn off the gene that makes the red pigment.

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And now they have managed, essentially, to push all those chemicals into the blue compound, so that now you get the blue rose. I think we should be able to look forward to buying a blue rose in the fairly near future. But again, obviously, it is not a food crop.

This is an example of metabolic engineering, where a metabolic pathway has now been changed from what it used to be. This relates back to the cancer-fighting compounds and is probably something that is going to happen more and more in the future, in food crops as well as in ornamentals.

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The other example I have of an appearance-type thing – and again this is technology from about 10 years ago, but it certainly has not been commercialised in Australia, because of all these issues of GM products – is a means of reducing browning in potatoes. There is a particular series of genes in potatoes, polyphenyl oxidase (PPO), which make fruit go black when you cut it. This slide shows that the GM tubers, where that gene has been turned off, do not go all black and horrible, whereas the normal ones do.

This PPO gene causes browning in lots of horticultural crops. For example, when you cut an apple and it goes brown in the air, that is because of the activity of this enzyme. So if you were to silence this enzyme, you could potentially have apples that don't go brown, for example. But again that has not been commercialised yet.

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I want to talk about fruit development. Although vegetables are obviously part of horticultural production, particularly in Australia, a lot of the important horticultural production is of fruit. And fruits, as you can see here, come in a wide variety of colours and shapes. In fact, there is an amazing variety of colours and shapes. There are fleshy fruits such as citrus and tomatoes, there are dry fruits such as macadamias, and there are more complex fruits such as strawberries and pineapples.

One of the issues that face horticultural biotechnology, and one of the really interesting things about horticulture is that you have got this wide variety of plant forms. But one of the issues is that, whereas some other crops such as wheat and so on are relatively dominated by a very limited number of crops, horticulture has many different kinds of crops. That causes particular problems in terms of biotechnology, just because the complexity that Ian Edwards mentioned is now attempting to be understood for a wide range of different sorts of plants.

What I want to point out here, however – to show that this is the way some of the future research in Australia is going – is that although there is this vast range of differently sized, shaped and coloured fruits, many of the genes involved in these processes are actually quite conserved. So although the appearance of the fruit is very different, a lot of the fundamental genes and a lot of the fundamental, underlying biology is actually quite conserved. I want to illustrate this in a couple of ways.

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One way of illustrating it is through colour. So really this is the same pathway again as we saw with the carnations. These are red-purply kind of colours which are called anthocyanins. For example, recent research shows that when you have white wine or red wine, there are a couple of genes which are responsible for that difference. Essentially, I think all white wine varieties that you might ever come across have the same two mutations as each other. So there's only really one white wine pair of genes out there.

CSIRO researchers in Adelaide have now identified that gene, and so now you can distinguish between red wine varieties and white wine varieties. And you could use that, obviously, for GM-type approaches. You could make a red chardonnay or you could make a white shiraz, for example, if you wanted to. Or you can follow it in breeding populations with these markers.

Of course, these colour things are also important in other crops; here I have shown apples. And so it appears that genes very similar genes to those that control colour in grapes are controlling colour in apples. And this is the same in corn and any other sort of plant you might see where you have different sorts of colours. It seems to be that this particular type of gene is very commonly involved in the red versus white varieties, and has arisen independently many different times in human endeavour over that 6000 years that Craig Cormick showed. And people have selected the white varieties.

I did notice, actually, that Craig mentioned beer at 6000 years ago. I don't know where wine comes in on that, but I think that is probably an important technological breakthrough that should be mentioned.

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The other thing that all these crops have in common is that naturally, at least, or as wild ones before being domesticated, they all produce seeds. For many horticultural crops you don't want to have seeds there. This is in crops like citrus or in table grapes, where you eat the seed but it is noticeably there and people don't like to eat it. They'd rather not have it there.

So other research has been aimed at citrus, in particular, but it also applies to table grapes and other crops. We are trying to find ways to reduce seed set. For example, you can use pollen sterility genes which stop the male part of the flower from producing pollen, and stop seed set that way. And you can produce genes which prevent seed development, so rather than having large woody seeds that you will notice when you are eating things like table grapes and citrus, you can get very small, soft seeds that aren't noticeable.

So those two things – the colour and the seed development – are under way in Australia.

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I want to mention where I think some of the future lies. The picture on this slide is of a generic fruit, not supposed to be anything in particular. I want to point out some of the areas that are in focus at the moment. (This is all about fruit quality and product differentiation.)

There is some interest in leaf and stem growth, mostly in relation to the leafy vegetables, for example. Some of the other key traits are things like health properties and flavour, which are obvious targets for biotechnology in horticultural crops. The aim is to produce things like cancer-fighting compounds and, essentially, to take advantage of the perceived quality benefit of some of these plants.

Obviously, you want to get rid of seeds in some crops. So there is change in the structure of the fruit, getting rid of seeds and getting the fruit to grow without seeds, and change in colour.

All of those – the content of the fruit, the appearance, its taste, all those sensory attributes – are the key targets for the future, I think, in horticultural biotechnology, particularly with regard to fruit development.

I just want to point out the little model plant on this slide, Arabidopsis, which again doesn't cause much controversy because it is completely a non-food crop. But a lot of the work involved in discovering the genes that control these sorts of processes is being done with model plants such as this plant here – which is partly a way of getting over the fact that there are so many different horticultural plants.

I would say that although Craig Cormick mentioned that there is some despondency about some of this biotechnology thing, from a scientific point of view we really are starting to understand now how this complicated structure, and seed set and seed development and fruit growth, are all occurring. It's really a fascinating time for understanding plant biology, and there are lots of exciting developments going on in terms of getting at some of the complexity of how these fruits work.

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Finally I want to say, in summary, where we are going from here. Obviously, GM crops are going to be a large part of the future, in terms of improved appearance, quality and health properties. These are all quality traits, not input traits.

But I just want to point out that although we do get hung up on GM crops, they are not the only way of delivering the advantages of biotechnology and they are not the only biotechnological things that we use in horticulture.

For example, there is faster breeding. One of the main problems with some of these horticultural crops is that some of them take so long to flower. There is a citrus breeder at our site who did a cross with two citrus trees. He did the cross 22 years ago, and the plant that he made from that cross still hasn't flowered. As you might imagine, that slows down breeding processes pretty badly. So faster-breeding things that might flower in only a few months, for example, would be a real benefit. And really that would apply to conventional non-GM breeding as well as GM.

As Ian Edwards and I have both mentioned, molecular markers are going to become more and more important, not only in terms of conventional breeding and marker-assisted selection – which is just really a way of improving your selection of progeny – but also in terms of some of these other ways of knocking out traits in a non-GM fashion.

And, finally, something that really distinguishes horticultural crops in some ways is that, because the plants seem to be much larger and certainly the perennial plants live for a long time, they tend to get a lot more individual management than your individual wheat plant would. So biotechnology can also be applied in that area, in terms of improving management of the plants from year to year.