This scanning electron microscope image shows a pea weevil
egg on a gall formed on a pea pod. The gall forms in response to plant
compounds called "bruchins." Magnified 60 times. (Albert Soeldner,
Oregon State University )
New Type of
Plant Regulator Discovered
By Kathryn Barry
May 15, 2000
A newly identified class of compounds helps pea plants defend themselves
against pea weevils, one of their most important insect enemies. And it's the
weevils themselves that produce the chemicals.
A team of scientists led by Agricultural
Research Service plant physiologist
Doss in Corvallis, Ore., and ARS chemist
James E. Oliver in
Beltsville, Md., report the discovery in tomorrow's edition of the
Proceedings of the National Academy of Sciences.
The compounds, named "bruchins" by the team, come into contact
with the plant when the weevil lays eggs on the pea pods. Within a few hours,
the plant starts producing a tumor or gall at the egg-laying site. By the time
the eggs hatch, a large gall or tumor becomes a barrier to the larvae, so they
can't burrow directly into the pod and feed on the peas inside.
This is the first time scientists have found chemicals that induce an
otherwise healthy plant to form a tumor to resist insect infestation.
The team also found that pea plants must possess a certain gene in order to
take advantage of the bruchins. In the 1990's, other researchers found that pea
plants with a certain genetic sequence, named Np, formed calluses in response
to weevil infestations. But this is the first time that scientists have
identified specific chemicals involved in the process.
Researchers at Oregon State University in
Corvallis, KOSAN Biosciences in Hayward,
Calif., and the ARS Regional Plant Introduction
Station in Pullman, Wash., collaborated on the discovery.
ARS is the chief research agency of the U.S.
Department of Agriculture.
Scientific contacts: Robert P. Doss, ARS
Crops Research Unit, Corvallis, Ore., phone (541) 750-8773, fax (541)
750-8764, firstname.lastname@example.org; or James
E. Oliver, ARS Insect
Chemical Ecology Laboratory, Beltsville, Md., phone (301) 504-8639, fax
(301) 504-6580, email@example.com.