UW Soybean Plant Health
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Some plants are predictably sensitive to a specific virus. This hypersensitivity is expressed as leaf symptoms shortly after exposure to the virus. The hypersensitive plants are called indicator plants, and are used as a bioassay to test for the presence of virus in an unknown sample. |
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Materials needed are gloves, sterile cotton swabs, rinse bottle, tissue grinding bags and carborundum - silicon carbide which is used as a tissue abrasive. Seedlings of the indicator plant are grown in the greenhouse. |
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Plant sap is made from the plant to be tested for virus by pulling off a symptomatic upper leaf ... |
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and placing the leaf in a sterile plastic bag. We add buffer solution to the bag, and grind the leaf tissue to release the virus particles into the buffer. |
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We sprinkle a bit of carborundum on the plant to be inoculated. Just a light dusting is sufficient to provide enough abrasion to introduce virus into the plant cells. |
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To inoculate the indicator plant, a cotton swab is immersed in plant sap... |
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and used to rub the surface of the test plant leaf firmly, but not with enough force to tear the leaf. |
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Then we rinse off the carborundum and excess sap from the leaf with water to remove compounds that could interfere with the infection process. |
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The indicator plants are placed in the greenhouse and checked daily for symptoms. If characteristic symptoms appear, we know that virus particles were present. |
Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: University of Wisconsin-Madison, Departments of Agronomy, Entomology, and Plant Pathology at www.plantpath.wisc.edu/soyhealth.