Serological methods for the detection of major grapevine viruses

Abstract

Serological methods are routinely used for the detection of many economically important grapevine viruses. The most commonly used format is the enzyme-linked immunosorbent assay (ELISA) which provides a robust, sensitive and rapid method to screen large numbers of samples from the field. A number of companies provide high-quality ELISA kits against most of the main viral pathogens infecting grapevines. Although virus titre shows seasonal fluctuations and the viruses may be unevenly distributed in vines, particularly for recent infection, ELISA provides reliable diagnosis if samples are collected at the optimal time in the specified vine tissue. Relative quantification can be achieved and the dynamic range of the assay can be extended by calculation of reaction rates from a kinetic assay and interpolation of these rates onto a dose-response curve. Additionally, comparing reaction rates obtained using monoclonal or polyclonal antibodies for detection can assist the identification of novel serotypes of a virus. Results from ELISA should be supplemented by molecular tests in critical situations, and vice versa, since some viral strains may not be detected by one or other type of tests. Antibodies can also be used to trap viruses or double-stranded RNA (immunocapture), thus providing an inexpensive and simple way to concentrate and purify viral RNA for subsequent molecular analyses. Further techniques that may assist serological detection of viruses are described.