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Evaluation of Three ELISA Methods as Alternatives to ISEM for Detection of the Wheat Spindle Streak Mosaic Strain of Wheat Yellow Mosaic Virus. K. R. Zagula, Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824. D. J. Barbara, D. W. Fulbright, and R. M. Lister. Institute of Horticultural Research, East Malling, Maidstone, Kent, ME19 6BJ, United Kingdom; Department of Botany and Plant Pathology, Michigan State University, East Lansing 48824; and Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907. Plant Dis. 74:974-978. Accepted for publication 14 May 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0974.

Immunosorbent electron microscopy (ISEM) has been used successfully for detecting wheat spindle streak mosaic virus (WSSMV) in infected wheat roots and leaves, but the method is laborious and time-consuming and requires the use of highly specialized equipment. To find a faster and routine alternative to ISEM, we evaluated direct double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) and indirect protein A ELISA (PAS-ELISA) in microtiter plates and direct double-antibody sandwich ELISA on nitrocellulose membranes (dot-ELISA). Although all three ELISA methods detected WSSMV in three types of extract from infected wheat leaves, the dilution end points for detection were at least eightfold greater in PAS- and dot-ELISA than in DAS-ELISA. The dilution end point for detecting WSSMV by ISEM was 16-fold less than that for DAS-ELISA and over 100-fold less than that for the other two ELISA methods. In a pilot study, PAS-ELISA readily detected WSSMV in symptomatic as well as asymptomatic leaves from field wheat. Despite somewhat high background reactions in PAS-ELISA, both dot- and PAS-ELISA were found to be sensitive techniques and should prove useful in confirming suspected WSSMV infections.