VIEW ARTICLE

Techniques

An Indirect Radioimmunoassay of Cauliflower Mosaic Virus. U. Melcher, Department of Biochemistry, Oklahoma State University, Stillwater, 74078; R. A. Hein(2), C. O. Gardner, Jr.,(3), M. W. Shockey(4), and R. C. Essenberg(5). (2)(3)(4)(5)Department of Biochemistry, Oklahoma State University, Stillwater, 74078. Phytopathology 70:954-957. Accepted for publication 26 March 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-954.

A radioimmunoassay procedure was developed that allows detection of 10-300 ng of cauliflower mosaic virus (CaMV) per sample. The assay utilized ¹²⁵I-CaMV, a rabbit antiserum to the virus, and either a second antibody or heat-killed Staphylococcus aureus. Triton X-100 and urea at concentrations of 0.2% and 0.2 M, respectively, lowered the amount of radioactive virus precipitated in the absence of, but not in the presence of, specific rabbit antiserum. At pH values of 7.0 and below, no competition could be seen on the addition of nonradioactive virus; therefore, assays were conducted at pH 8.0. Extracts of turnip leaves did not interfere with the assay except at very low virus concentrations. Virus was detected in extracts of leaves of plants infected with CaMV. The addition of Triton X-100 and urea to the leaf extracts was necessary for maximum detection of viral antigen. The levels of virus detected in turnip leaves by this assay exceeded the levels that were obtained on isolation and purification of CaMV from these leaves. The assay allows the detection of less than 1 μg of virus per gram of tissue.