Farming News

Op Ed By Professor Michael Wilson

When Jose MacDonald raised the issue of ladybirds being damaged by GM potatoes (FN, Aug 28), through feeding on the affected aphids, she was demonstrating a general misunderstanding of the scientific rationale, significance and conclusions of work carried out at the SCRI on GM potatoes, aphids and ladybirds.

Although doubtless intended to outrage your readers, it is wrong to equate such preliminary, fundamental research and risk assessment studies on a possible new gene construct to control aphids with the dozens of successful commercial GM crops, now approved and grown worldwide.

These have negotiated 10 to 12 years of unprecedented precautionary risk assessments and release regulations (not least, involving over 25,000 closely monitored field trials) to obtain environmental human health and safety approvals.

Such logic and tactics are akin to denouncing all pharmaceuticals and therapeutic medicines simply because, as always happens, some drugs under development or in clinical trials, fail on efficacy or safety criteria.

GENETICALLY DURABLE

Over the past 12 years, in common with many thousands of scientists in hundreds of independent university, government and corporate laboratories around the world, SCRI staff have been testing the potential of novel classes of plant and other proteins to provide effective, alternative, safe and genetically durable forms of resistance against the multitude of pests and pathogens which presently account for average global crop yield losses of around 25 to 30 per cent.

Unfortunately, many of these pests and pathogens are evolving more rapidly than conventional breeders can develop new resistant crop varieties against them. This genetic "cat-and-mouse" game has been a constant feature of our domestication, breeding and selection of crops over the past 10,000 years.

At present, the only feasible way to minimise such depredations, for those who can afford it, is by the extensive use of pesticides, fungicides and, worst of all, nematicides. The facts and figures, and our inexorable reliance on these, albeit agronomically "smarter" (compared with those of 50 years ago) and environmentally less-damaging agrochemicals, make sombre reading for the sustainability of our finite, high-yielding land resource.

Yet there are few realistic alternatives (certainly not organic farming) to deal with escalating future demand for greater quantities of ever-higher quality foods by a rapidly rising human population.

Sadly, for many devastating pests and pathogens, no resistance gene(s) exist in our seedbanks or germplasm collections and, even where such genes are available, they may be only partially effective.

Moreover, so-called traditional "natural" breeding methods to create a new resistance trait in an existing selected variety (e.g. using chemical or radiation mutagenesis), or to transfer resistance between species, varieties or cultivars, are extremely slow and unpredictable.

Since 1983, scientists have been able to introduce a few specific genes, for a known and desired characteristic, into an already selected and utilised crop variety. The added gene is usually expressed as a single new protein, with a particular function, and at vanishingly low levels in the so-called transgenic plant. Typically, the amount of new protein varies from being virtually undetectable by the most sensitive analytical methods, to less than 0.1 per cent of the total plant protein content.

As with traditional breeding, individual GM plant lines which display the desired (additional) trait are then selected, but in this case, without having lost any of the previous beneficial features of the crop variety. Thereafter begins an extensive, intensive and rigorous programme of health and safety testing, unprecedented for the product of any other technology, and certainly not required for food crops produced by so-called "natural" breeding methods.

To put the values above in perspective, it is not unusual for, say, virus-infected non-GM fruit or vegetables to contain foreign (viral) proteins at levels up to 10 per cent of total protein, or for any plant under attack or stress to be expressing complex arrays of defence toxins and the like.

The millions of tonnes of GM crops grown and consumed over the past several years throughout the world, largely outside Europe, have been thoroughly tested for any possible allergy effects of the new protein, and for any conceivable, albeit remote, health or safety risk.

Rarely, but occasionally at an early stage, some effect may be noted which results in the particular GM variety being discarded. This was the entirely predictable and scientifically unsurprising fate of a pilot research project which involved adding the gene for an allergenic brazil nut protein into corn.

Similarly, while it may be valid for some basic research purpose, to introduce an equivalent peanut allergen into potato, this is clearly not going to create a credible new GM food crop!

Such curiosity-driven early-stage experiments were exploited by anti-technology activist groups and the media to spread fear, confusion and misinformation about GM crops and foods among the public.

Many years of scientific research have shown that some members of a class of natural plant proteins known as lectins have potent anti-nematode and anti-insect feeding activities. However, we also know that some members of this class of proteins, if uncooked, are toxic to humans and animals. This is not news. After all, lectins and other proteins are part of the natural defence mechanisms of many leguminous species (eg red kidney beans).

When the gene for a lectin from the snowdrop was introduced into potato it reduced feeding aphid numbers by 50 per cent. Aphids transmit potato leafroll virus (PLRV), which causes severe yield losses, and are (poorly) controlled by spraying with insecticides. Consequently, SCRI is interested in testing possible alternative biological control strategies to reduce aphid numbers and hence the incidence of PLRV. By genetic engineering, a new gene and thus a protein is expressed at low levels inside cells of the crop plant where minimal amounts can have the maximum effect against the target pest or pathogen, unlike the widespread use of chemical sprays.

If farmers do not have to spray their crop with insecticides, non-target, beneficial insects can also survive and flourish. Among these will be ladybirds, which naturally feed on aphids and so provide some additional biological control of these pests.

Experiments at SCRI showed that female ladybirds force-fed (for 14 days) only on aphids reared on potato leaves (not tubers) that expressed the snowdrop lectin lived about half as long and about twice as many of their eggs failed to hatch, compared with control ladybirds fed on aphids from non-GM potatoes.

Field experiments have not yet been done to assess whether the effects seen on aphids (or ladybirds) in the laboratory are reproducible or even significant. Addition-al environmental stresses, the lack of chemical spray stress, the presence of alternative non-GM potato crops as feeding sources and many other factors may increase or decrease the efficacy, and hence the utility of the snow-drop protein as an aphid control agent. In the field, lady-birds may feed elsewhere, or show more or less fecundity.

That is why we do such experiments - to discover the truth and new knowledge, not to distort facts and interpret reality selectively to create biased propoganda, meaningless mantras or scaremongering media headlines.

I am confident that potatoes expressing the snowdrop lectin are NOT imminent as a human food crop. Even If we found that this or any other lectin, or any new protein, provided safer and more sustainable biological control of aphids, the entire gamut of risk assessments, safety testing, field trialling, allergy testing and regulatory approvals still remains to be navigated.

What does all this mean? Avoiding, or at least reducing, the use of pesticides is good news for the environment. It makes sound economic sense for farmers and consumers, who also benefit from the reduced risk of pesticide residues on or in their fresh foods and drinking water.

SOUND EVIDENCE

Around the world, and for the last several years, thousands of farmers (NOT the agricultural companies) have been reporting huge reductions in pesticide and herbicide application rates by growing particular GM crops (usually 20-50 per cent, but sometimes even 100 per cent, ie no pesticide use at all!) with parallel increases in crop yield, typically between five and 15 per cent.

For me, these open and verifiable facts provide sound evidence of the economic, health and sustainable environmental benefits actually being delivered by the new GM crops.

I am unaware of any "doomsday superweeds" or "activist-eating vegetables" at large in the agricultural environment. With each passing year and millions of GM crops grown and consumed without incident, all the speculative "what ifs", "mights" and "maybes" used by the eco-technopanic groups assume the priority and credibility they deserve.