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Etiology

Characterization of Sweet Clover Necrotic Mosaic Virus. C. Hiruki, Department of Plant Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada; D. V. Rao(2), M. H. Chen(3), T. Okuno(4), and Gina Figueiredo(5). (2)(3)(4)(5)Department of Plant Science, University of Alberta, Edmonton, Alberta, T6G 2P5, Canada. Phytopathology 74:482-486. Accepted for publication 30 November 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-482.

A previously undescribed virus was isolated from sweet clover (Melilotus officinalis) plants showing systemic mosaic associated with ringspots and veinal necrosis. It was readily sap transmissible to 16 of 25 species tested including both leguminous and nonleguminous plants. Sap or purified preparations contained polyhedral particles 35 nm in diameter that sedimented at a velocity of 123 S as a single component. The virus particles contained a bipartite genome with RNA molecular weights (M_r) of 1.35 × 10⁶ and 0.55 × 10⁶ daltons and a single species of coat protein with an M_r of 38,000 daltons. Amorphous inclusions were observed in the cytoplasm of infected epidermal cells. The virus resembled red clover necrotic mosaic virus and clover primary leaf necrosis in particle morphology. However, it was clearly distinguished by host range, molecular weights of RNA and protein, and serological properties. The name sweet clover necrotic mosaic virus is proposed for the virus.