Studies on the viruses of Japanese radish mosaic diseases

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1. This paper deals with serological experiments using the radish P virus. The virus used as immunizing antigen was the isolate P0, which was obtained from a mosaic radish plant in Matsudo, Chiba Prefecture, in May 1956, and was maintained in a greenhouse by successive juice inoculation on turnip plants.2. By a combined procedure of salting-out with ammonium sulfate and differential centrifuging, a partially purified virus preparation was obtained from infected turnip leaf juice. Antiserum was prepared by injecting rabbits with this virus preparation. The rabbits were given 7∼8 intravenous injections (equivalent to total leaf juice volume of 150ml), at 2∼7 days intervals. The titer of the antiserum obtained was 1:10, 000∼1:40, 000, in precipitation reaction tests.3. The antiserum reacted specifically with leaf juice of Brassica rapa var. glabra, Raphanus sativus, Brassica pekinensis, Petunia hybrida, Chrysanthemum coronarium and Spinacia oleracea, which were infected with the radish P virus; also with leaf juice of mosaic radish plants collected in the suburbs of Tokyo, which were judged, by host range tests, to be infected with the radish P virus. The antiserum did not react with leaf juice of healthy plants, plants infected with radish Q virus, radish R virus, cucumber mosaic virus, or several other viruses. In absorption tests, the antiserum completely absorbed the radish P virus, but not other viruses.4. Virus dilution end-point was: ×300 in agglutination reaction on slide glasses, and ×2, 000 in precipitation reaction, using turnip leaf juice; 0.002∼0.005mg/ml (virus dry weight basis), using purified virus preparations.5. Out of 231 mosaic radish plants collected in the suburbs of Tokyo, 106 reacted with the antiserum. In host range tests of the viruses involved, radish P virus, radish Q virus, radish R virus, and cucumber mosaic virus were detected. As judged from the combined results of these serological tests and host range tests, 31 out of 76 plants tested were found to be infected with a single virus, the rest being infected with two, three, or four viruses.