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Radish Enation Mosaic Virus

1968; Phytopathological Society of Japan; Volume: 34; Issue: 2 Linguagem: Inglês

10.3186/jjphytopath.34.129

1882-0484

Hiroshi Tochihara,

Plant and Fungal Interactions Research

This paper deals with the identification of a virus which was isolated from a mosaic radish plant in Omagari, Akita Prefecture, in Octobar, 1960.The virus was purified from systemically infected radish leaves (subvariety Kameido) by the following procedure: treatment at 50-53°C for 10min. →repeated shaking with 20% chloroform, salting-out by 0.4 saturated ammonium sulfate, and cycles of differential centrifuging (80, 000G, 60min. and 10, 000G, 10min.) →density gradient centrifugation in 20-50 (or 20-60)% sucrose at 35, 000rpm for 120-150min. (two distinct opalescent bands in the middle) →cycles of differential centrifuging→dialysis against water.In inoculation tests, the lower band showed a high infectivity, the upper band showed only little infectivity, although the inoculated preparations were far from being a complete separation. Both bands contained particles of similar size and shape, when examined under electronmicroscope after being fixed in 1% formalin and stained with 1% phosphotungstic acid. The particles are spherical and about 25-30mμ in diameter. There were very little "empty" particles in both preparations. The purified preparation showed a maximum UV absorption at 258-260mμ, the absorption curve being that of typical nucleoprotein with 260/280=1.57, and max/min=1.34-1.37. Thermal inactivation point was 65°C (10min. treatment of crude juice), while there was considerable loss of infectivity by treatment at 60°C for 10min.The virus was readily transmitted by sap-inoculation. The virus was transmitted by the striped flea beetle (Phyllotreta striolata), but not by cabbage stink bug (Eurydama rugosa), two species of aphids (Myzus persicae and Lipaphis pseudobrassicae). There was no transmission through seeds of radish plant, nor through soil.Various plants were mechanically inoculated with sap from infected radish plants, carborundum being applied to the leaves before inoculation. Many cruciferous plants were found to be susceptible to the virus. The symptoms on infected radish plants were characteristic enation (cf. fig. 3), mosaic, necrosis, and distortion of leaves. Turnip produced necrotic local lesions, and also developed systemic mosaic. Cabbage and cauliflower showed faint susceptibility. Globe amaranth (Gomphrena globosa) produced chloroticspots on the inoculated leaves 7-10 days after inoculation, and rarely developed topnecrosis. Spinach produced chlorotic-spots on the inoculated leaves, and also developed top-necrosis. Petunia was proved to be symptomless carrier, the virus being localized in the inoculated leaves. Chenopodium amaranticolor and C. album produced necrotic local lesions. The following plants were not susceptible: tobacco (Bright Yellow, Xanthi, White Burley), Nicotiana glutinosa, tomato, pepper, kidney bean, cowpea, broad bean, garden pea, cucumber, pumpkin, Chrysanthemum coronarium, morning-glory, beet, rape, Datura stramonium, and Physalis floridana.To produce antiserum, rabbits were given three muscular injections at intervals of 20 days, of a partially purified virus preparation homogenized with an equal volume of Freund's complete adjuvant. The antiserum obtained had a titer of 1: 5, 000 in the precipitation reaction, the antiserum also reacted with crude juice from diseased radish leaves or with purified virus preparations in agar-gel double diffusion. As the antiserum was produced by using a partially purified virus preparation, crude juice from diseased radish leaves produced non specific as well as specific zones.