Stunt Disease of Japanese Radish

Abstract

1. The severeness of a stunt disease of radish at Sizuoka in the autumn of 1939 attracted our intention. Studies on symptoms, transmission, host range and properties of the Japanese stunt virus has been made, the results of which are presented in this paper.2. Heavily diseased radish is stunted and show remarkable reduction in size of root. The symptoms of the diseased leaf consist of vein-clearing, ruffle, mottle, malformation, vein-banding, enation. and string-like protoruded vein. Mottle also appears on the surface of pod and peduncle.3. X-body has not been observed in the diseased leaf tissue.4. This stunt virus is readily transmissible by mechanical inoculation using carborundum as an abrasive. The incubation period ranges from 6 to 15 days.5. The stunt virus is detected in roots, leaves, peduncles, pods and unmature seeds of the affected plant. The virus in the seeds is active in its milky stage, but seems to be not in mature seeds.6. It seems to be inactivated by heating for 10 minutes at 70°C, and does not cause infection when press-out juice is diluted up to 15000 times. It passes through the Berkefeld's filters, V, N and W. The virus retains its infectivity in vitro after ageing for 23 days, and in dry for 39 days in dry disease leaf.7. Succesful attempts were made in the green-house to transmit this stunt virus by means of the green peach aphid (Myzus persicae SULZ.) and the false cabbage aphid (Rhopalosiphum pseudobrassicae DAVIS).8. The host range of the stunt virus includes 10 species of plants representing 4 genera in 4 families. In the family Cruciferae, infection was obtained on rape, leaf mustard, pe-tsai, radish, stock, leaf-mustard, pe-tsui, pak-choi, turnip, Santosai (Brassica pekinesis RUPR var. dentata MATSUM. et NAKAI), Mibuna (Brassica japonica SIEB. var. indivisa MAKINO).9. The stunt disease of radish in question, appears to be a new one as there exists considerable differences between other cruciferous mosaic diseases.