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Etiology

A New Serotype of Sweet Clover Necrotic Mosaic Virus. Hanumanth R. Pappu, Graduate research assistant, Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5; C. Hiruki, and N. Inouye. A. G. McCalla research professor, and visiting associate professor, respectively, Department of Plant Science, University of Alberta, Edmonton, Alberta, Canada T6G 2P5. Phytopathology 78:1343-1348. Accepted for publication 9 May 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-1343.

A new serotype of sweet clover necrotic mosaic virus (SCNMV) isolated from alfalfa (Medicago sativa L.) was characterized on the basis of serology, physicochemical properties, host range, and symptomatology. The antiserum of the new isolate (SCNMV-59) distinguished the type strain (SCNMV-38) from SCNMV-59 by homologous spur formation, whereas the antiserum of SCNMV-38 gave a reaction of identity with both antigens. Intra-gel cross-absorption tests between the two serotypes demonstrated the presence of heterospecific antibodies in anti-SCNMV-38 serum that specifically reacted with SCNMV-59 antigen. The molecular mass of the coat protein of the new isolate was about 39,000 daltons when estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric points of the two serotypes were in the range of 4.85–5.00. Agarose gel electrophoresis of virions showed distinct mobility differences between the two serotypes. The new serotype could also be distinguished from the type strain on the basis of certain differences in host range and symptomatology on selected host plants.