Fungus' Protein Causes Weed Cells to Self Destruct

By Jan Suszkiw
February 18, 2000

Weeds are notoriously stubborn, but researchers may be on the verge of turning the pesky plants into their own worst enemy.

Their approach involves spraying the weeds with a natural protein derived from the soil fungus Fusarium oxysporum. Upon entering natural leaf openings called stomata, the fungus' protein causes a specific self-defense mechanism to shift into maximum overdrive.

The defense, called a hypersensitive response, normally helps weeds cordon off infection by instructing nearby cells to self-destruct. But in lab, greenhouse, and small-scale field trials, spraying the protein causes a mass cellular suicide instead. In dandelions, for example, this kills the weed's affected leaves three to 24 hours later.

The finding, by Agricultural Research Service scientists, may open the door to a natural herbicide that farmers, organic growers or homeowners could spray to check broadleaf weeds like dandelion, yellow star thistle, pigweed or northern jointvetch.

Plant pathologist Bryan Bailey and colleagues are exploring the possibility at several ARS labs--Biocontrol of Plant Diseases, Weed Science, and Soybean and Alfalfa Research. ARS is USDA's chief research agency.

Bailey's team originally discovered the protein, called Nep1, while trying to understand how some fusarium fungi cause disease in crops like corn. Studies begun in 1998 ruled out the protein's role in causing crop disease, but also revealed its potential as a biological herbicide.

The team reports their findings in the January-February issue of Weed Science. Interestingly, Nep1 only affects broadleaf weeds of the dicot family with cell receptors that can detect the protein. This suggests it could be sprayed onto monocot crops like corn, wheat, or even turfgrass without causing harm. Another possibility is spraying Nep1 to clear away certain cover crops, like hairy vetch, prior to planting.

A longer article about the team's discovery appears in the February issue of Agricultural Research magazine. Click here to read it on the web.

Scientific contact: Bryan Bailey, ARS Biocontrol of Plant Diseases Laboratory, Beltsville, Md., phone (301) 504-6653/5682, fax (301) 504-5968, bbailey@asrr.arsusda.gov.