ORGANIC farmers and biotech firms alike stand to benefit from a potent
biopesticide that kills a multitude of insect pests without harming beneficial
species. The biopesticide, a strain of Bacillus thuringiensis,
produces more toxins than any other known strain of the bacterium.
The supercharged B. thuringiensis was discovered by Egyptian
researchers in cadavers of larvae from the pink bollworm, which ravages cotton
plantations. 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.
Farmers have been using strains of B. thuringiensis as organic
biopesticides for three decades. But whereas existing commercial strains make
just one or two Bt toxins that kill the pests, the Egyptian variant makes a
staggering 18.
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鈥淲e were amazed and very happy when we stumbled on it,鈥� says Yehia Osman,
head of the team which isolated the bacterium at the Agricultural Genetic
Engineering Research Institute in Giza, Egypt. 鈥淭his is the most potent Bt
strain yet found, and has the most diversified host range.鈥�
So far, 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.
鈥淚t鈥檚 an ideal to have a single isolate with this much activity,鈥� says Osman,
who presented his findings earlier this month at the annual meeting of the
American Society for Microbiology in Chicago. 鈥淭he insects would have a hard
time developing resistance to this.鈥�
But recent reports have called into question the safety of existing
commercial Bt strains. French researchers found that mice contracted fatal lung
infections after inhaling the bacteria
(This Week, 29 May, p 4). And at the
Chicago meeting, Azam Tayabali of Health Canada, the Canadian health ministry,
revealed the results of a study which showed that bacterial spores in some
commercial Bt strains can kill human cells. He recommended that farmers spraying
Bt mixtures wear proper protective gear.
But Osman and his colleagues insist their tests indicate that the Bt strains
they are using will prove safe for organic farmers to apply as a biopesticide:
鈥淲e鈥檝e done toxicity tests in rats and fish, and didn鈥檛 get any adverse effects
at all,鈥� Osman told New 杏吧原创. 鈥淎nd so far, during all tests, it
doesn鈥檛 have effects on non-target organisms.鈥� The Egyptian Ministry of
Agriculture is now undertaking trials.
Osman鈥檚 team has worked out the DNA sequences of several of the genes
producing the toxins. The institute has patented the commercial application of
the bacterium, and has an agreement with the Iowa seed company Pioneer Hi-Bred
to potentially license use of the genes in genetically modified crops.