| Extracts:
- United States farmers received government subsidies to grow Roundup Ready soybean instead of the varieties they were used to. So they were financially better off replacing their old varieties, even though they had to pay Monsanto for the seeds and the herbicide, and the yield from Roundup Ready soybean is less than that of other varieties by about 10%. One reason for the reduced yield is that Roundup Ready soybean does not cope with heat stress as well as other unmodified varieties.
- So far as human health is concerned, the base sequence of the DNA involved in these transfers needs to be adjusted so that Bt proteins expressed in plants are no longer allergenic to humans. There is no technological barrier to this being done. A decade ago it was assumed that these Bt proteins were toxic only to insects. Now we know that they also affect mammals, by affecting the lining of the intestine, and by causing allergenic responses as well. This was the basic problems with Starlink maize produced by Aventis, which as approved in the USA for animal food, but not for human consumption. A catastrophic mixup occurred, resulting in StarLink maize getting into a variety of human foods, including Kellogg’s Cornflakes. An expensive recall of maize products from countries as far away as Japan followed this incident.
Sunday at 8.45am, repeated Mondays at 2.15pm
Presented by Robyn Williams
 print
Seeds of Concern: The Genetic Manipulation of Plants - Part One
Sunday 11 April 2004
Summary
Dr David Murray is a scientist and conservationist with a lifelong interest in plants. He's also the author of a book called Seeds of Concern: The Genetic Manipulation of Plants. In part one of his two part talk he criticises both extreme positions of the genetically modified plant debate and sets the scene for the eventual acceptance of some genetically modified plants by organic growers and environmentalists.
Program Transcript
Robyn Williams: In the past few weeks doors have closed against GM crops in most Australian States. In New Zealand the door is partly open, as it is in Britain. A mixed report for a kind of agriculture that’s supposed to be the way forward, scientifically. But that’s a generalisation.
Today Dr David Murray wants to give us specifics. He’s written much on plants and how to grow them with least harm to the environment, and his latest book is on GM.
David Murray: Whenever I am asked whether I am opposed to genetically modified plants, or in favour of them, I have to answer, ‘Both, it depends on the plant, the purpose of the modification and the way the plant was modified.’ Some people have difficulty understanding my equivocation, because this has become a strongly polarised debate, with participants either firmly in favour of gene technology, or absolutely against it. Someone who reviewed several chapters of my recent book ‘Seeds of Concern’, prior to publication, could not understand why I was opposed to some transgenic plants, such as crop plants made resistant to systemic herbicides, but with suitable precautions I was in favour of others. He felt that I ought to be opposed to all genetically modified plants simply because they were genetically modified plants. I disagree. Dogmatic opposition like this is akin to religious fanaticism, and is not an attitude that any scientist should adopt. Today I am going to criticise both extreme positions, and, I hope, set the scene for eventual acceptance of some genetically modified plants by organic growers and environmentalists.
Let’s start with this ‘absolutely opposed’ group. I think it is unreasonable to be totally opposed to the release of genetically modified plants solely because of the way in which they were developed. The argument that genetic engineers are ‘playing God’ when they interfere with the properties of plants by adding new genes or subtracting old ones is entirely specious. We don’t apply this argument in any other sphere of human endeavour.
When a doctor saves the life of someone who would have died without his or her intervention, no-one objects on the basis that the doctor is interfering with the natural course of events. Quite the opposite, the medical profession as a whole is praised for saving human lives.
So far as plant breeding is concerned, our ancestors have been influencing the properties of plants for more than 10,000 years. The selection of pods that remained closed instead of flying open at maturity made harvesting legumes like peas and chick peas much more efficient, and these changes became the norm for cultivated legumes in the Near East at least 5,000 years ago. Every time a crop was grown and seed was saved from the healthiest plants, selection took place. Different varieties travelled widely, and became adapted to many diverse environments. For some cultivated plants there are now hundreds or even thousands of distinct cultivars. Our current crop plants all come from long lines of survivors. Furthermore, many valuable improvements have been achieved by plant breeders over the past 230 years, using conventional crossing, observation of the progeny, and selection. The achievements of our pioneering plant breeders, people like Thomas Andrew Knight, Gregor Mendel, and Luther Burbank, are too little appreciated.
Opposition to a genetically modified plant for a definite reason is not the same as being dogmatically opposed to the methodology. The first genetically modified plants to be released and grown on a large scale had inherent problems that I regard as serious faults. These plants should not have been released. Monsanto’s Roundup Ready soybean is a prime example. What I have proposed in my book is an empirical approach. This means that every genetically modified plant that someone wants to release should be examined on its merits after having been tested, thoroughly and independently. This means having committees composed of people who will assess proposals according to the techniques employed in bringing about the genetic modification, and who are able to judge the likelihood of the plants themselves being able to interbreed with other cultivars of the same crop, or with allied weed species. Genetic escape does need to be controlled. Our regulators also need to be more alert to the possibility of unintended effects of gene transfer.
The present Federal committee structure makes it too easy for genetically modified plants to be approved, because it is fragmented, and there is no single committee that takes a holistic overview. Pesticide use is regarded as irrelevant, and independent safety tests of genetically modified plant products are not conducted. We take too much on trust. Far too much notice has been taken of those who display unbridled optimism about gene technology, who dismiss the public’s fears out of hand as merely ‘conjectural’. Those who insist that we need have no concerns are perhaps displaying an unwillingness to question. And those who justify the release of GM plants simply because they might have a major role in feeding the world in the coming century are likely to be disappointed. Evidence already shows that most of the genetically modified plants released so far have lower yields per unit area than existing unmodified varieties.
Both sides accuse one another of misrepresentation, especially when bodies such as the New South Wales Farmers’ Association hold their annual conference. But overly enthusiastic proponents of genetically modified plants have alienated public support for the new technology by frequently claiming the unlikely or the impossible, or putting forward frivolous breeding goals, such as producing a blue rose or grasses that light up in the dark when you tread on them.
Among other things, proponents have claimed that genetically modified plants:
- differ from the unmodified variety by only a single gene;
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- represent greater precision in gene selection and placement than through standard breeding techniques;
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- afford growers opportunities for ‘better weed control’;
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- allow growers to use less pesticide; and
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- improve agricultural efficiency.
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Misinformation is rife. How often do we hear this ‘single gene’ nonsense, especially from people who know full well that what is transferred is not a single gene, but a transgene construct. Not only is the desired gene transferred, but a promoter gene sequence that will help switch this gene on, and allow it to be expressed in the right tissues at the right time. As well, there is at least one ‘reporter’ or marker gene. Often this confers resistance to an antibiotic or a herbicide, so that when the plant cells have been treated, the majority that have not been transformed will die when exposed to the antibiotic or herbicide in tissue culture. The surviving cells are the ones most likely to have incorporated the transgene construct into the host genome, and these are then encouraged to differentiate and develop into new plants.
The promoter has often been taken from cauliflower mosaic virus, which means that the gene or genes that follow this promoter will be expressed in every part of the plant, including the pollen grains. This lack of tissue specificity is undesirable, and in the case of GM maize in the south of the USA, has led to the release of insecticidal pollen grains that coat the leaves of milkweed, the food source for larvae of the monarch butterfly. There is also evidence that this particular viral sequence can be removed by invading cauliflower mosaic virus, thus rendering the transferred genes useless and unexpressed in plants susceptible to this virus.
The inclusion of marker genes that confer resistance to antibiotics has also been widely criticised because of the possible transfer of such genes to other organisms, including bacteria. Such ‘horizontal’ gene transfer has been demonstrated from leaves of four transgenic plants to a fungus breaking down those leaves. The acquisition of multiple antibiotic resistance by disease-causing bacteria is a major medical problem, examined in the ABC-TV program Catalyst on the 24th July 2003. Steps should be taken to prevent the uncontrolled spread of antibiotic resistance among bacteria wherever possible, and this means rejecting any GM plant that contains a gene for antibiotic resistance.
This does not mean rejecting all genetically modified plants. A colour test for transformation provides a simple alternative assay that does not run the same risks. Another safer option is to include the gene for a fluorescent protein from a jellyfish, Aequorea victoria, so that successfully transformed cells can be detected using a fluorescence microscope.
One of the most successful approaches to transforming plants involves the use of plasmids from the soil bacterium Agrobacterium. Plasmids are small pieces of bacterial DNA located outside the bacterial chromosome. Several species in the genus Agrobacterium cause plant disorders such as crown gall and hairy roots. They act by having their plasmids incorporated into the plant genome. For genetic modification, the genes and sequences to be transferred can be arranged inside the border regions of an Agrobacterium plasmid. Other genes normally present can be deleted, so that the disease normally caused does not run its full course. Such a strain of Agrobacterium is said to have been ‘disarmed’. The beauty of this system is that gene transfer is taking full advantage of bacterial genes that already have the natural capability of being integrated into host plant genomes with a minimum of disruption.
‘Precision’ is not really the right word to describe what happens when most transgenic plants are produced. No one can tell in advance exactly where the transgene construct is going to be placed amongst the chromosomes of the host plant, nor can scientists predict how many copies of the construct will be integrated. This all depends on the activities of enzymes that cut and rejoin DNA. So there are many possible insertion sites. Sometimes pieces of the construct will be inserted as well as, or instead of, the full construct. The downside of all transformation techniques is interruption of pre-existing gene and non-coding DNA sequences, and hence interference with an already well adapted and fully functional genome. This could confer some unforeseen disadvantage on the genetically modified plant, so it is a matter of trial and much error to discover which are the best transformed plants from any particular batch.
Over-expression of introduced genes is a problem with some methods, such as biolistics, which is shooting gene preparations into plant tissue with tiny projectiles. The apparatus that enables this to happen is called a ‘gas gun’. When gas guns were first being developed, they had to be licenced to operators by the police. According to Dr Nigel Steele Scott from CSIRO Horticulture, a policeman testing one such apparatus in 1990 accidentally shot himself in the foot. Fortunately there was no subsequent outbreak of transgenic police in South Australia, where a three-year moratorium on the release of transgenic plants has just been announced.
‘Better weed control’ is the mantra of those giant agribusinesses that have modified crop plants to be resistant to commonly used herbicides. Better for whom? Let’s look again at Monsanto’s ‘Roundup Ready’ soybean. Roundup is Monsanto’s trade name for their preparation of the herbicide glyphosate, which is a compound that inhibits the synthesis of aromatic amino acids in plants and other organisms. In the USA growers can now spray their soybean crop with glyphosate three to five times before harvest, whereas previously on a single application of a different pre-emergent herbicide would have been possible. Because glyphosate is systemic, that means carried inside the transport tissues of the plant, glyphosate taken up by the plant is delivered to all parts of the plant, including the seeds. Not all of this glyphosate is detoxified or broken down by the genetically modified soybean. Some is left inside the seeds. Instead of maintaining our food standard for residual glyphosate, the Australia-New Zealand Food Authority raised the tolerance for US soybeans imported to Australia from 0.1 mg glyphosate to 20 mg glyphosate per kilogram of beans. This represents a massive 200-fold increase and this extra glyphosate can’t be washed off, it is inside the seeds.
United States farmers received government subsidies to grow Roundup Ready soybean instead of the varieties they were used to. So they were financially better off replacing their old varieties, even though they had to pay Monsanto for the seeds and the herbicide, and the yield from Roundup Ready soybean is less than that of other varieties by about 10%. One reason for the reduced yield is that Roundup Ready soybean does not cope with heat stress as well as other unmodified varieties. With increasingly hot summer seasons in the Northern Hemisphere, American farmers are realising the increased risk of crop failure with Roundup Ready soybean, which now represents about 60% of the US production, rather than the 90% it used to at its peak in about 1997. With herbicide-resistant crop plants, farmers are being encouraged to use just the one herbicide repeatedly, but agronomists are advising farmers that this is not a good idea, this is a proven recipe for generating herbicide-resistant weeds, which further complicate farm management.
Health-conscious consumers are looking for reduced contamination of foods with herbicides and other pesticides. The extent of adverse long-term health effects from increased consumption of compounds like glyphosate cannot be predicted. It is best to assume there is no such thing as a safe agricultural chemical. They are constantly being retired with hindsight, recent examples being the triazine herbicides, such as atrazine and simazine, which have been shown to be endocrine disruptors. Avoidance is the safest policy, although this requires determination. A recent survey in Victoria found that all samples of organic produce tested, had pesticide residues at or below detectable limits, raising confidence in the current systems for certifying organic produce which of course is produced without the aid of artificial pesticides.
Robyn Williams: So there are some objections to GM crops. More next week from David Murray, and a few plaudits as well.
His book, ‘Seeds of Concern’ is published by University of New South Wales Press.
I’m Robyn Williams.
Guests on this program:
Dr David Murray
Scientist and Conservationist
Author
Gwynneville
New South Wales
Publications:
Seeds of Concern: The Genetic Manipulation of Plants
Author: David Murray
Publisher: University of New South Wales Press
Presenter: Robyn Williams
Producer: Brigitte Seega
Source: http://www.abc.net.au/rn/science/ockham/stories/s1083266.htm
Sunday at 8.45am, repeated Mondays at 2.15pm
Presented by Robyn Williams
print
Seeds of Concern: The Genetic Manipulation of Plants - Part Two
Sunday 18 April 2004
Summary
Dr David Murray, author of 'Seeds of Concern', continutes his discussion of the genetically modified plant debate. This week he looks at various crop plants and the unexpected consequence of genetic modification to achieve herbicide resistance
Program Transcript
Robyn Williams: ‘Seeds of Concern’ is the title of Dr David Murray’s book about the genetic manipulation of plants. Last week he said it is foolish to be absolutely for or absolutely against such crops, and explained why. This time he elaborates the argument.
David Murray.
David Murray: In my previous program, I was particularly critical of those genetically modified plants that had been made resistant to systemic herbicides, because the products of these plants contain much higher contents of herbicides than do those from unmodified plants. Furthermore, such products are difficult to avoid in processed foods. The company GeneScan reported in Australian Biotechnology News on 20th September 2002, that genetically modified material had been found in 28% of 1,139 commercial samples submitted to them for analysis in the previous 12 months. Most of these samples were of imported soy and maize products, which means that Roundup Ready soybean, and Bt-protein producing and herbicide-resistant maize were being detected. Fortunately, we are not dependent on American production of soybeans, and their fallible separation methods. New varieties of soybean suitable for growing under Australian conditions were bred by CSIRO using conventional methods, and released to growers in Queensland and northern New South Wales. The variety Curringa is ideal for making tofu, and is now being grown in the Riverina. This crop will mainly be exported to Japan for processing.
The canola story is quite complicated, and today’s account must be very brief. When I visited CSIRO Plant Industry in preparing for writing my book, I spoke to a number of researchers about their projects. One of them, Dr Allan Green, is interested in bringing about improvements to plant oil composition. He expressed great relief that he was not working on canola.
Canola is a type of oilseed rape, Brassica napus, first developed in Canada more than 20 years ago. The seed oil has a much reduced content of erucic acid, which is a long-chain fatty acid that is toxic to humans. The oil has a high content of monounsaturated fatty acid, but its polyunsaturated fatty acid content at about 30% is too high for it to be considered a safe cooking oil, like olive oil. Moreover, the pressed seed residues can be toxic to animals and poultry because of their glucosinolate and tannin contents. Glucosinolates are precursors of mustard oils, produced in members of only 16 families of flowering plants. One kind of herbicide-resistant canola has been found to have a substantially increased glucosinolate content as an unexpected consequence of genetic modification to achieve its herbicide resistance.
Bayer CropSciences, formerly Aventis, have successfully applied to release several genetically modified canola lines called InVigor in Australia. These lines are all resistant to the herbicide glufosinate. The very first herbicide-resistant canola plants were developed by conventional breeding techniques, assisted by embryo rescue and tissue culture. Varieties like ‘Siren’ were resistant to the now banned triazine herbicides. Because there was an alteration in a chloroplast protein, Siren did not readily transfer the chloroplast gene that governed this property to other varieties of canola. All this has changed. Genetically modified varieties of canola given resistance to single herbicides such as glyphosate or glufosinate will readily cross with one another, and with unmodified varieties. Safety margins of 400 metres as proposed for Bayer’s ‘InVigor’ canola are inadequate. Canola resistant to three different herbicides has developed all by itself in Canada, well, with a little bit of help from pollinating insects.
Bob Willock is a Canadian farmer who visited Australia and was interviewed on the ABC program The Country Hour on 6th March, 2003. Just as Percy Schmeiser had done in 2002, he warned Australian farmers about the difficulties in growing the new kinds of herbicide-resistant canola. He described his own experience. He had to spray the crop several times while it was growing to suppress weeds. Because of poor market prices, by the time he had paid for seeds and herbicide, he was not getting a large enough return to make a living. He switched to growing an older variety of canola organically, which means that he had to deal with weeds by physical means, but as a consequence his market price increased and his overheads decreased. One method of controlling weeds in canola is choosing a high enough planting density so that weeds are suppressed by shading and competition. Bob Willock still faces the problem of other farmers’ crops of herbicide-resistant canola crossing with his own, so he needs a fresh supply of true-top-type seeds each season, produced well away from herbicide-resistant crops.
Here in Australia agronomists are encouraging wheat farmers to alternate a legume such as chick pea or broad bean with their wheat crops, instead of canola. Because legumes host nitrogen-fixing bacteria in nodules on their roots, they need no nitrogenous fertiliser themselves, and the residues of their root systems left in the ground make a substantial contribution to the nitrogen requirement of the following wheat crop. This contribution can be as much as one-third of the nitrogen that would otherwise need to be supplied as synthetic fertiliser. Rotation of cereals with legumes is an ancient practice that makes very good sense, and should be part of any movement towards sustainable agriculture. And whereas the production of annual legumes is absolutely essential for human nutrition and health, the same cannot be said for canola.
Canola just keeps taking nutrients that have to be replaced with yet more synthetic fertiliser. The phosphorus taken into one tonne of canola seed is more than twice as much as the phosphorus taken into one tonne of wheat, barley or oats. And because the seeds are readily lost prior to harvest, canola itself is a weed of the next crop in the same soil. Why would any thinking farmer invite herbicide-resistant canola onto his or her property as a weed?
Pesticide use is supposed to be reduced with crop plants engineered to express an insecticidal protein or proteins, from the soil bacterium Bacillus thuringiensis, Bt for short. The theory is that plants producing this bacterial protein in their leaves will kill more of the larvae feasting on the leaves, thus ensuring a reasonable yield for the crop, and avoiding the need to spray insecticides. In Australia, Bt-cotton is the first cab off the rank in this category of genetically modified plants. Cotton normally requires the most intensive spraying of insecticides of any crop plant. Up to 14 different pesticides are needed. Monsanto and CSIRO Plant Industry have collaborated to introduce Monsanto’s Bt-cotton, called INGARD, and progeny of this cotton have been crossed with some of Australia’s own best cultivars.
In practice though, there is something wrong with the control of expression of the bacterial gene in cotton. It works for the first half of the growing season but fails to be expressed in the more important second half. Then growers have to spray insecticides in just the same way as they would for non-genetically modified cotton varieties. The fundamental flaw in this scenario is that insect pests are being offered just a single Bt protein at a time, which is likely to reinforce inherited resistance. Normally Bacillus thuringiensis produces a suite of distinct crystalline proteins that interact synergistically to wipe out susceptible insect larvae. It is unlikely that any insect pest could develop simultaneous resistance to a complex collection of such proteins, and that is why CSIRO Plant Industry staff are now introducing more than one Bt gene to cotton. I would like to see this done with half-a-dozen Bt genes at once, so that the modified crop plants more closely mimicked the original bacterium.
Many growers, including home gardeners, would appreciate this technology being applied to other members of the genus Brassica, such as cabbages, Brussels sprouts, cauliflower and broccoli, to effectively dislodge the cabbage white butterfly as a major pest. The green caterpillars hide by day and move by night.
Dependence on predators such as birds is unreliable, and no grower can inspect every single plant every single day. Brassica leaves producing a suite of Bt proteins, would suffer less insect damage and be more productive, without the need to spray insecticides, or even DiPel, a preparation of whole Bacillus thuringiensis bacteria approved by organic codes.
So far as human health is concerned, the base sequence of the DNA involved in these transfers needs to be adjusted so that Bt proteins expressed in plants are no longer allergenic to humans. There is no technological barrier to this being done. A decade ago it was assumed that these Bt proteins were toxic only to insects. Now we know that they also affect mammals, by affecting the lining of the intestine, and by causing allergenic responses as well. This was the basic problems with Starlink maize produced by Aventis, which as approved in the USA for animal food, but not for human consumption. A catastrophic mixup occurred, resulting in StarLink maize getting into a variety of human foods, including Kellogg’s Cornflakes. An expensive recall of maize products from countries as far away as Japan followed this incident.
(transcript cut)
Robyn Williams: The complexity of the GM arguments. They’re presented by Dr David Murray in his book ‘Seeds of Concern’, published by University of New South Wales Press.
Next week, Sue Taylor in Melbourne describes a brilliant breakthrough in the conservation of Australian birds.
I’m Robyn Williams.
Guests on this program:
Dr David Murray
Scientist and Conservationist
Author
Gwynneville
New South Wales
Publications:
Seeds of Concern: The Genetic Manipulation of Plants
Author: David Murray
Publisher: University of New South Wales Press
Presenter: Robyn Williams
Producer: Brigitte Seega
Source: http://www.abc.net.au/rn/science/ockham/stories/s1088066.htm
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