DETECTION OF VIRUS-INFECTION IN PLANTS AND DIFFERENTIATION BETWEEN COEXISTING VIRUSES BY MONOCLONAL-ANTIBODIES TO DOUBLE-STRANDED-RNA

Monoclonal antibodies to double-stranded RNA (dsRNA) are described for use as a universal diagnostic tool to detect infection in plants by RNA viruses. Crude nucleic acid extracts from plants infected with one of 25 different viruses were examined by sandwich-ELISA and immunoblotting. In comparison to the corresponding controls elevated dsRNA concentrations were found in 21 infected samples by ELISA; virus-specific dsRNA bands from 18 viruses were detected by immunoblotting. Using this method the identification of infecting virus is potentially possible on the basis of the electrophoretic banding pattern of the dsRNA, which in turn depends on the number, molecular weight and/or thermodynamic stability of the dsRNA species present in the extract. Immunoblot analyses in combination with temperature-gradient gel electrophoresis were used to demonstrate that the four individual genomic dsRNAs of the coexisting beet cryptic viruses BCV1 and BCV2 can be distinguished from one another and from other dsRNAs present in the extracts. It is shown that the thermal denaturation profiles and the T-m-values of the main structural transitions of BCV genomic dsRNAs are essentially the same in viruses from sugar beet as well as from wild Beta maritima. The reliability of dsRNA-immunoblotting for detecting virus infection in plants is discussed. Its use is especially recommended for the detection and characterization of cryptic viruses.