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Wednesday, June 16, 1999 Published at 22:53 GMT 23:53 UK


Sci/Tech

Organic pesticide may aid GM crops

The new bacterium was found in the corpses of bollworm larvae

A super-deadly pesticide used by organic farmers has been discovered, but it may be used for the genetic modification (GM) of crops, which many organic farmers oppose.

Food under the microscope
The new pesticide is a virulent strain of a bacterium called Bacillus thuringiensis (Bt). It was discovered by researchers at the Agricultural Genetic Engineering Research Institute in Giza, Egypt.

They isolated the bacterium in the corpses of larvae from the pink bollworm, which ravages cotton plantations.

Farmers have been using strains of Bt as organic bio-pesticides for three decades. But whereas existing commercial strains make just one or two toxins that kill pests, the Egyptian version manufactures 18.

Most potent yet

The researchers have already sequenced and patented some of the key genes that make the toxins and hope to license a seed company to use them in genetically-modified crops.

"We were amazed and very happy when we stumbled on it," said the research team's leader Yehia Osman, in New Scientist magazine.

"This is the most potent Bt strain yet found, and has the most diversified host range."

So far, Dr Osman and his colleagues have discovered that the toxic proteins kill moths, coleopteran beetles and dipteran insects such as mosquitoes. As an added bonus, the toxins also kill nematode worms.

No resistance

"It's ideal to have a single isolate with this much activity. The insects would have a hard time developing resistance to this," says Dr Osman.

"We've done toxicity tests in rats and fish, and didn't get any adverse effects at all. So far, during all tests, it doesn't have effects on non-target organisms."

The Egyptian Ministry of Agriculture is now conducting trials.

Plant calls in support

Another non-GM way of fighting plant pests has been suggested by researchers at the University of California Davis.

They discovered that when the common tomato it is attacked by the beet armyworm, it secretes a chemical which attracts the worm's natural enemy - a tiny parasitic wasp.


[ image: The tomato's secretion calls in the worm killers]
The tomato's secretion calls in the worm killers
The team showed that spraying the tomatoes with jasmonic acid, the chemical the tomato produces to set off the alarm call, resulted in twice as many armyworm caterpillars being killed.

They believe that stimulating the natural defence mechanism of the tomato would be a good way to deal with pests.

"The plants are essentially sending up a chemical 'smoke signal' to attract the wasps," said Jennifer Thaler, a post-doctoral fellow at UC Davis.

"The results suggest that artificially induced plant resistance and the use of biological controls in the form of naturally occurring enemies can be combined to control crop pests."

When the worm moves in to feed on the tomato, the plant produces more of the chemical responsible for the leafy, green odour in plants.

The wasp smells the compound, locates the plant and then pierces the caterpillar's flesh and places a single egg inside. The wasp larva hatches and feeds on the worm before creating a cocoon and hatching into an adult.



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Internet Links


UC Davis Intergrated Pest Management Programme

New Scientist

Nature

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