VIEW ARTICLE

Techniques

Rapid Magnetic Microsphere Enzyme Immunoassay for Potato Virus X and Potato Leafroll Virus. Ernest E. Banttari, Professor, Department of Plant Pathology, University of Minnesota, St. Paul 55108; David L. Clapper(2), Sheau-Ping Hu(3), Kristin M. Daws(4), and S. M. Paul Khurana(5). (2)(3)(4)Manager of biological research, biochemist, and biochemist, respectively, Bio-Metric Systems, Inc., 9924 West Seventy-Fourth Street, Eden Prairie, MN 55344; (5)Virologist, Division of Plant Pathology, Central Potato Research Institute, Shimla, India. Phytopathology 81:1039-1042. Accepted for publication 30 April 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-1039.

A magnetic microsphere enzyme-linked immunoassay was developed for detection of potato virus X (PVX) and potato leafroll virus (PLRV) in potatoes. Analyte, microspheres with covalently coupled antibody and antibody-enzyme conjugate, were mixed, incubated together for 10 min, magnetically separated from sap, and washed with buffer three times; finally, substrates containing a 5-bromo-4-chloro-3-indoyl phosphate/nitro blue tetrazolium or p-nitrophenyl phosphate were added. Color development (A₅₆₂) or (A₄₀₅) occurred in positive samples within 15–20 min. Detection sensitivity for PVX was 1–3 ng of purified virus diluted into buffer or healthy leaf sap or PVX-infected potato sap diluted × 1,000 in healthy potato sap. Detection sensitivity for PLRV was ?10 ng of purified virus diluted into healthy sap or PLRV-infected sap diluted × 1,000 in healthy potato sap. This assay can be completed within 30–45 min and provides assay sensitivities comparable to double antibody sandwich enzyme-linked immunosorbent assays on polystyrene or nitrocellulose solid phase carriers for these viruses.