Detection and serological relationships of Cymbidium mosaic potexvirus isolates

Twenty-two isolates of Cymbidium mosaic virus (CyMV) were isolated from 35 orchid plants suspected of being infected with CyMV. Among the three method s used for detecting CyMV, immunoelectron microscopy (IEM-1) was shown to b e the most sensitive method, being able to detect the virus in 71.43% of su spected CyMV-infected plants while the electron microscopic method and the indexing plant method could detect 51.43 and 42.86%, respectively. Out of 1 2 symptomless plants investigated, 25% were found by IEM-1 method to be inf ected with the virus. Purified CyMV were flexuous rods having lengths betwe en 470-490 nm. A few end-to-end aggregates were also observed and the 280/2 60 absorbance ratios were from 0.884 to 0.929. The yield of CyMV was 31.07 to 44.09 mg per kg of Datura leaves. Antibodies against purified CyMV D2 we re produced in rabbits and hens. The antibody titers in the yolk and sera o f hens indicated that 0.5 mg of virus per immunization efficiently generate d an abundant supply of IgY in the yolk, however 1 mg of virus per immuniza tion gave a stronger immune response in both sera and yolk. The average yie lds of IgY were 6.5 0.6 and 9.4+/-0.9 mg/ml of yolk in the group that recei ved 0.5 mg and the group that received 1.0 mg of the virus, respectively. P ositive ELISA reactions were observed in 18 and 20 of 22 CyMV isolates when detected with rabbit IgG and IgY, respectively, demonstrating that those i solates were serologically related and the ELISA reactions were shown to be stronger with IgY than those with rabbit IgG in most isolates. The degree of reaction between the CyMV isolates, O-2 and O-4, and IgY was less than t hat of the other isolates. The two isolates, Ds and Cats, gave negative rea ctions to rabbit IgG. The results of ELISA assays showed that the homologou s serological reaction was not consistently stronger than the heterologous one. Twelve isolates out of twenty-two gave stronger reactions than the hom ologous antigen (CyMV D-2) when IgY was used as the detecting antibody whil e nine isolates gave stronger reactions when using rabbit IgG. No reactions were observed with other plant viruses and plant proteins from healthy Dat ura.