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New Type of Plant Regulator Discovered / May 15, 2000 / News from the USDA Agricultural Research Service

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Scanning electron microscope image shows a pea weevil egg on a gall formed on a pea pod.

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 Stelljes
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 Robert P. 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 Horticultural Crops Research Unit, Corvallis, Ore., phone (541) 750-8773, fax (541) 750-8764, dossr@bcc.orst.edu; or James E. Oliver, ARS Insect Chemical Ecology Laboratory, Beltsville, Md., phone (301) 504-8639, fax (301) 504-6580, joliver@asrr.arsusda.gov.

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