2-Plants: Insects thrive on GM 'pest-killing' crops
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TITLE: Insects thrive on GM 'pest-killing' crops
SOURCE: The Independent, UK, by Geoffrey Lean
DATE: Mar 30, 2003
------------------ archive: http://www.gene.ch/genet.html ------------------
Insects thrive on GM 'pest-killing' crops
Genetically modified crops specially engineered to kill pests in fact
nourish them, startling new research has revealed.
The research - which has taken even the most ardent opponents of GM crops
by surprise - radically undermines one of the key benefits claimed for
them. And it suggests that they may be an even greater threat to organic
farming than has been envisaged.
It strikes at the heart of one of the main lines of current genetic
engineering in agriculture: breeding crops that come equipped with their
Biotech companies have added genes from a naturally occurring poison,
Bacillus thuringiensis (Bt), which is widely used as a pesticide by
organic farmers. The engineered crops have spread fast. The amount of
land planted with them worldwide grew more than 25-fold - from four
million acres in 1996 to well over 100 million acres (44.2m hectares) in
2000 - and the global market is expected to be worth $25bn (£16bn) by 2010.
Drawbacks have already emerged, with pests becoming resistant to the
toxin. Environmentalists say that resistance develops all the faster
because the insects are constantly exposed to it in the plants, rather
than being subject to occasional spraying.
But the new research - by scientists at Imperial College London and the
Universidad Simon Rodrigues in Caracas, Venezuela - adds an alarming new
twist, suggesting that pests can actually use the poison as a food and
that the crops, rather than automatically controlling them, can actually
help them to thrive.
They fed resistant larvae of the diamondback moth - an increasingly
troublesome pest in the southern US and in the tropics - on normal
cabbage leaves and ones that had been treated with a Bt toxin. The larvae
eating the treated leaves grew much faster and bigger - with a 56 per
cent higher growth rate.
They found that the larvae "are able to digest and utilise" the toxin and
may be using it as a "supplementary food", adding that the presence of
the poison "could have modified the nutritional balance in plants" for them.
And they conclude: "Bt transgenic crops could therefore have
unanticipated nutritionally favourable effects, increasing the fitness of
Pete Riley, food campaigner for Friends of the Earth, said last night:
"This is just another example of the unexpected harmful effects of GM crops.
"If Friends of the Earth had come up with the suggestion that crops
engineered to kill pests could make them bigger and healthier instead, we
would have been laughed out of court.
"It destroys the industry's entire case that insect-resistant GM crops
can have anything to do with sustainable farming."
Patrick Holden, director of the Soil Association, said it showed that GM
crops posed an even "worse threat to organic farming than had previously
been imagined". Breed- ing resistance to the Bt insecticide sometimes
used by organic farmers was bad enough, but problems would become even
greater if pests treated it as "a high-protein diet".
Volume 6 Issue 3
IDEAS AND PERSPECTIVES
Could Bt transgenic crops have nutritionally favourable effects on
Ali H. Sayyed1, Hugo Cerda1,2* and Denis J. Wright1
We present an idea that larvae of some Bacillus thuringiensis (Bt )
resistant populations of the diamondback moth, Plutella xylostella (L.),
may be able to use Cry1Ac toxin derived from Bt as a supplementary food
protein. Bt transgenic crops could therefore have unanticipated
nutritionally favourable effects, increasing the fitness of resistant
populations. This idea is discussed in the context of the evolution of
resistance to Bt transgenic crops.