The purpose of this chapter is to illustrate some techniques exploiting the properties of viral nucleic acids by which plant viruses can be identified and the diseases they induce diagnosed. These methods are basically the same as those used in other fields of biology and, therefore, some details of their description may appear repetitious, if not cumbersome. However, the current literature indicates that a direct transfer without adjustment of these technologies to plant virology is not always possible, as many factors (sap constituents of different plant species, age of the plant, time of sampling, etc.) may seriously affect resolution, sensitivity, and specificity.
