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Serological Differentiation of Some Strains of Alfalfa Mosaic Virus with Polyclonal Antibodies. M. R. Hajimorad, Research associate, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064; R. I. B. Francki, Reader, Department of Plant Pathology, Waite Agricultural Research Institute, University of Adelaide, Glen Osmond, South Australia 5064. Phytopathology 81:603-610. Accepted for publication 8 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/Phyto-81-603.

Five biologically distinct but antigenically similar alfalfa mosaic virus (AMV) strains were tested for minor antigenic differences by immuno-diffusion tests and indirect enzyme-linked immunosorbent assay (ELISA) by using antisera elicited to native and glutaraldehyde-fixed AMV particles of each of the virus strains. In addition, antisera to coat protein preparations of two of the strains were also used. In immunodiffusion tests with antisera to fixed virus particles and either fixed or native virus preparations as test antigens, no antigenic differences were detected among any of the strains. However, antisera to native AMV particles revealed antigenic differences among all five strains, although some were easier to detect than others. The differences were more readily revealed, however, when fixed virus preparations were used as test antigens. Similar differences were also detected when antisera elicited to AMV coat protein preparations were used. In general, strain-specific differences among the AMV strains were more difficult to detect by indirect-ELISA. It is concluded that some antibodies to strain-specific epitopes on AMV are present in antisera elicited in response to native AMV particles or their isolated coat proteins, but that these epitopes are more easily detected when fixed particles are used as test antigens. It is also concluded that the strain-specific epitopes were metatopes.