Studies on the white clover mosaic virus

Abstract

White clover mosaic virus (WCMV) was isolated from Ladino white clover showing mottling in Morioka. In the host range study, the legumes Astragalis sinicus, Canavallia ensiformis, Crotalaria spectabilis, Lathyrus odoratus, Phaseolus vulgaris, Pisum sativum, Trifolium hybridum, T. incarnatum, T. pratense, T. subterraneum, Vicia faba, V. villosa, V. sativa, Vigna sesquipedalis and V. sinensis were systemically infected. Local infection was obtained in the legumes Dolichos lablab, Glycine max, Medicago sativa, Lupinus leteus, Phaseolus angularis and P. radiatus, the non leguminous species Datura stramonium, Nicotiana rustica, N. sylvestris, Petunia hybrida, Physalis floridana, Citrullus vulgaris, Cucumis sativus, Ipomoea purpurea and Antirrhium majus. The virus was not transmitted to Nicotiana tobacum, N. glutinosa, Beta vulgaris, Chenopodium amaranticola, Spinacea oleracea and Gomphrena globosa.Test with Cuscuta sojagena indicated that dodder transmission occurs on rare occasions, if it occurs. In insect transmission experiment with Acyrthosiphon pisum, Aphis cravora and Myzus persicae, no transmission was obtained. It seemed that the virus was not transmitted through seed.The thermal inactivation point of the virus laid between 70-75°C and the dilution end point between 1:105 and 1:106. In the aging test, the virus was still active after 60 days, but not after 90 days at 25°C, while it withstood storage for 91 days at room temperature.In the study of electron microscope, the occurrence of flexible rods, about 450mμ in length, was observed, and the mass of the virus particles was evident by the ultra-thin sections was observed. Corner inclusion bodies were observed in the infected cells.Precipitation reaction between the virus isolated in Japan and the antiserum against Pratt's isolate was positive.The virus was found occurring naturally on red clover as well as on Ladino white clover.It is supposed on the basis of host range, symptomatology, transmission, physical properties, morphology of the particles and serological reaction that the virus belongs to the group of white clover mosaic virus that has been reported in several countries.