A Novel Detection and Identification Technique for Plant Viruses: Rapid Immunofilter Paper Assay (RIPA). Shinya Tsuda, NODAI Research Institute, Tokyo University of Agriculture, Setagaya, Tokyo 156, Japan. Mitsuro Kameya-Iwaki, Kaoru Hanada, Yoshiko Kouda, Mikio Hikata, and Keiichi Tomaru. National Agriculture Research Center, Tsukuba, Ibaraki 305, Japan; Japan Synthetic Rubber Co. Ltd., Tsukuba, Ibaraki 305, Japan; and NODAI Research Institute, Tokyo University of Agriculture, Setagaya, Tokyo 156, Japan. Plant Dis. 76:466-469. Accepted for publication 5 November 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0466.

A rapid immunofilter paper assay (RIPA) for cucumber mosaic virus (CMV) or tobacco mosaic virus (TMV) was developed using latex beads coated with antibodies to either virus. White latex-coated antibody was immobilized as a solid in a line on the surface near the bottom of a filter paper strip. The bottom end of this paper strip was dipped for 3 min into a mixture of leaf extract from an infected plant and dyed-latex coated with the virus antibody. A colored band appeared on the line where the white latex had been immobilized. With RIPA, as little as 5 ng/ml of purified TMV or 50 ng/ml of purified CMV could be detected with the naked eye. In the extract from infected tobacco plants, TMV was detected to a dilution of 10^–7, and CMV was detected to a dilution of 10^–5 with the naked eye. The conditions for coating antibody to the latex beads were best at pH 7.2 using Tris-buffered saline and a 100-?g/ml concentration of antibody. When RIPA was applied to the extract of infected plants of 13 species in six families, CMV was detected from all species. When filter paper strips were measured by chromatoscanner, each sample virus could be detected at concentrations 10 to 100 times lower than concentrations detected with the naked eye. The sensibility of RIPA measured by chromatoscanner was similar to sensibilities of ELISA tests for CMV.