Identification of a New Strain of Maize Dwarf Mosaic Virus. L. L. McDaniel, Postdoctoral Associate, Department of Plant Pathology, Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. D. T. Gordon, Professor, Department of Plant Pathology, Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Plant Dis. 69:602-607. Accepted for publication 10 February 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-602.

A maize virus isolate from Texas induced symptoms on maize (Zea mays) resembling those incited by maize dwarf mosaic virus strain A (MDMV-A). The host range of this mechanically transmitted isolate was confined to the Gramineae and was similar to that of MDMV-A, except that it infected oats (Avena sativa). Maize inbreds CG1, CI 44, Pa32, and Pa405 were immune to infection. Properties of this virus in Oh28 maize sap were dilution end point, 10^–3 to 10^–4; longevity in vitro, 2–3 days at room temperature; and thermal inactivation point, 55–60 C. The virus was transmitted from maize to maize nonpersistently by Rhopalosiphum maidis. It was not seed-transmitted in johnsongrass (Sorghum halepense), oats, or Oh28 maize. Infective virus was recovered from diseased tissues stored 17 mo at 3 and –23 C. The virus had flexuous, rod-shaped particles 690–800 nm long. Pinwheel and bundle inclusions, but no laminated aggregates, were observed in the cytoplasm of infected cells. The virus was partially purified by a protocol that featured 0.5 M potassium phosphate buffer (pH 7.0) at all steps, chloroform clarification, and high-speed and sucrose density gradient centrifugation. Isolate sedimentation characteristics matched those of MDMV-A in rate-zonal centrifuged sucrose density gradients. No serological relationships were established between this isolate and Ohio isolates of MDMV-A and MDMV-B when tested with antisera to the two strains by agar gel double-diffusion, microprecipitin, or double-antibody sandwich enzyme-linked immunosorbent assay. The isolate, considered a new strain of MDMV, was designated the oat-infecting or MDMV-O strain.