Variability in Enzyme-Linked Immunosorbent Assays and Control of Experimental Error by Use of Experimental Designs. E. M. BAUSKE, Department of Horticulture, Auburn University, Auburn, AL 36849. A. D. HEWINGS, USDA-ARS Crop Protection Research Unit and Department of Plant Pathology, University of Illinois, Urbana 61801; and F. L. KOLB and S. G. CARMER, Department of Agronomy, University of Illinois, Urbana 61801. Plant Dis. 78:1206-1210. Accepted for publication 29 August 1994. This article is in the public domain and not copyrightable It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1994. DOI: 10.1094/PD-78-1206.

Seven uniformity trials were done on Nunc-Immuno IF and Dynatech Immulon I "U" microplates with two monoclonal triple-antibody sandwich enzyme-linked immunosorbent assays to determine if an experimental design was necessary to control plate variability. A single uniform extract of either oat (cv. Clintland 64) tissue infected with barley yellow dwarf luteovirus (BYDV-PAV-IL) or soybean (cv. Williams 82) tissue infected with soybean mosaic potyvirus (SMV-G5) was prepared, and samples were placed in the wells of eight microplates used for each trial. For whole plates, mean absorbances varied within trials and coefficients of variability ranged from 3.8 to 20.3%. Seventeen of the 56 plates tested had one to five wells with absorbances that were outliers from the normal distribution. Nonrandomized designs of two replications of 48 treatments were also assigned to each plate. When replications of a treatment were paired in either rows or columns, differences between treatment means were confounded with row and column differences, indicating the need for an experimental design on microplates. Both the randomized complete block design and the alpha (0,1) one-restrictional resolvable incomplete block design allowed for more precision than the completely randomized design. The smaller, incomplete blocks of the alpha design afforded slightly more precision than the larger, complete blocks of the randomized complete block design.