Despite the huge improvements made in diagnostic technologies over the last 30 years, the detection and identification of plant viruses remains a major challenge, for many different reasons. Firstly the number of pathogens faced by virologists has grown hugely, with around 1200 different plant viruses now listed as full or tentative species. Keeping pace with this ever expanding viral biodiversity is an immense challenge. Certain individual hosts, for example many of the major solanaceous crops including potato, tomato and petunia, can be infected by numerous different viruses and viroids. To provide even a basic screening package, based on pathogens known to occur frequently in these hosts, requires multiple individual tests to be performed on eachsample, and the use of combinations of different technologies; predominantly immunological (e.g. ELISA) and molecular (e.g. PCR) methods, with biological testing (e.g. sap inoculation) and electron microscopy also required to detect certain pathogens. This type of parallel testing is time consuming and expensive, and requires diagnostic services to invest heavily in different technologies.
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