Scientists find new tool to protect crops
By Mark Weinraub
WASHINGTON, June 25 (Reuters) - A new type of genetically engineered plant may
hold the key to providing farmers with pest-free fields, researchers said on
The new breed of plants would emit a toxin that would kill insects that fed on
them, said Richard ffrench-Constant (Eds: Correct spelling), an associate
professor of insect toxicology at the University of Wisconsin-Madison.
Working with other scientists at the University of Wisconsin-Madison, ffrench-
Constant isolated a gene in nematodes, a parasite that kills insects by
infecting them with a bacteria called Photorhabdus luminescens (Pht). The
scientists hope to be able to encode plants with this gene, making them deadly
to many types of insect invaders.
Pht has so far shown no harmful effects to humans or the environment, ffrench-
It will be a few years before these plants hit the market, but ``it's raising
its head as a useful alternative,'' ffrench-Constant said in a telephone
``These new toxins are highly efficient killers of insects and they hold for
the future the same promise first revealed in Bt (Bacillus thuringiensis) more
than 30 years ago,'' he said in a statement.
Currently, plants can be developed to resist pests by expressing Bacillus
thuringiensis toxins. These genetically engineered plants, introduced a few
years ago, are extremely popular, particularly with cotton and corn farmers.
However, since this breed only emits Bt toxins, insects may begin to develop a
tolerance to Bt toxins, a situation that severely hampered the effectiveness
of the pesticide DDT, ffrench-Constant said.
Introducing a new breed of pest-resistant plant that uses a different type of
weapon, like Pht, greatly reduces the chance that insects could built up an
``What we have with Photorhabdus and other bacteria is a natural source,
almost an infinite variety of toxic molecules,'' ffrench-Constant said in a
statement. ``We can't afford to hook ourselves to a single bacterium or a
Once the Pht toxin is fully developed there will be many different methods to
deploy it, ffrench-Constant said.
Farmers could either plant different breeds of genetically engineered crops,
some that express Bt and some that express Pht toxins, in one field, exposing
insects to both. Farmers could also rotate which breed they use every season.
Scientists could also develop a plant that would express both types of toxins
that would attack pests in two different ways.
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