Three Filamentous Viruses Isolated from Sweet Potato in Japan.

Abstract

Three filamentous viruses were isolated from sweet potato by sap inoculation. The M-isolate infected Ipomoea spp., Nicotiana tabacum, N. benthamiana, Datura stramonium, Chenopodium quinoa, and C. amaranticolor. The Mo-isolate infected Ipomoea spp., C. quinoa and C. amaranticolor. The C-isolate infected only Ipomoea spp. The infectivities of the M-, Mo- and C-isolates were lost at dilutions of 1:1,000-1:10,000, 1:1,000-1:10,000 and 1:100-1:1,000, respectively, or after storage for one day at 20.degree. C. The thermal inactivation points were 50-60.degree. C, 60-70.degree. C and 70-80.degree. C, respectively. Virus particles of the M- and Mo-isolates were 750-810 nm and 850-880 nm long, respectively. The C-isolate was 710-760 nm and 1,430-1,510 nm long. The particle diameter of all isolates was 13 nm. The M-isolate was easily transmitted by Myzus persicae but Mo- and C-isolates were not. The serological relationship between the M-isolate and sweet potato latent virus (SPLV) occurring in Taiwan was observed by serologically specific electron microscopy using protein A gold (SSEM-PAG). The Mo-isolate strongly reacted with antisera against sweet potato feathery mottle virus-russet crack strain (SPFMV-RC) found in the United States and SPFMV in Japan. No close serological relationship was found among three isolates. These results suggested that M- and Mo-isolates are strains of SPLV and SPFMV, respectively, and the C-isolate is a new virus, which we named sweet potato symptomless virus (SPSV)