Detection of cucumber mosaic virus in some ornamental plants and elimination of nonspecific ELISA reactions

During surveys carried out in 2008 in the nurseries of some ornamental and medical plants, about 90 plant samples belonging to six plant species were collected. Cucumber mosaic virus (CMV) was detected by routinely double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) in most tested plants. In Vinca rosea, Ocimum basilicum and Pelargonium sp., which reacted positively for CMV, 100% of the samples were infected. High absorbance values were obtained when extracts were prepared from these species and then examined by DAS-ELISA. The results indicated that CMV concentration on O. basilicum is greater than 50 μg ml^?1 when compared with purified CMV standards. High absorbance values occur even under conditions fully unsuitable for the detection of antigens. This result suggested that the strong ELISA absorbance values were nonspecific reactions with materials in plant extracts. So, other detection methods including dot blot, Western blot and bioassay was used for comparing with ELISA test. The nonspecific reactions were substantiated when CMV was not detected by dot blot and Western blot. Also, infectious CMV was not detected in bioassay involving inoculation of extracts onto Chenopodium amaranticolor and Nicotiana tabacum var. White Burley plants as indicator hosts. Addition of bovine serum albumin (BSA) or polyvinylpyrolidene (PVP) to extraction buffer or to wells after IgG coating for DAS-ELISA reduced nonspecific reactions. Finally, CMV was isolated from V. rosea symptomatic plants, which give a positive reaction by DAS-ELISA, dot blot, Western blot and bioassay. CMV vinca-isolate was identified based on transmission, host range, serological tests, purification and electron microscope.