Testing for Sudden Oak Death – Enzyme Immunoassay (EIA) Method

The EIA method uses antibodies to identify the presence of proteins or carbohydrates unique to Phytophthora. The EIA method can serve as a low-cost alternate pre-screen before PCR analysis. Samples are taken from symptomatic leaves and placed in sample tubes along with a small glass bead.
Sampling Leaves
Extraction
A tissue homogenizer is used to rapidly agitate the sample tube and the glass bead mascerates the leaf tissue (think of a tiny paint shaker). An extraction solution is added to leach out the plant sap. The liquid exudate is centrifuged and stored frozen for later analysis.
The commecially available assay uses a microtiter plate formatted DAS ELISA protocol to detect the presence of Phytophthora antigens. User’s Guide. An enzyme substrate changes color when Phytophthora is present in the sample. The results may be observed by eye or quantified with an optical plate reader. Manufacturer’s Page.
EIA Assay Plate


Pros and Cons of the EIA method:
Pro:
– Provides a rapid and cost effective prescreen for Phytophthora.
– Less false negative results compared to culturing.
– Assay is faster and more robust when compared to PCR.
– Relatively low cost compared to PCR.

Con:
– Relatively expensive compared to culturing.
– Requires some specialized equipment.
– Cross reacts with other Phytophthoras (false positive for SOD) and the results need to be interpreted with caution, preferably by someone with expertise in the field.

Jump to Other SOD Diagnostic Methods:
Immunostrips – Culturing – EIA Analysis – PCR Analysis

The UC Berkeley Forest Pathology and Mycology Laboratory does not provide a SOD testing service. For information on SOD testing please visit www.suddenoakdeath.org

This activity possible thanks to funding from:
USDA Forest Service, State and Private Forestry
The Gordon and Betty Moore Foundation
Agdia, Inc. http://www.agdia.com

Disclaimer: Mention of any company, trade name, or commercial product does not constitute endorsement by the University of California or recommendation for use.