Diagnosis and Detection of Plum Pox Virus: State-Of-The-Art and Future Options

The control of Plum pox virus (PPV) and the management of sharka, require the use of reliable detection methods. Despite the considerable efforts made in many countries, PPV has been reported in most of the important Prunus growing countries worldwide. Moreover, it is occasionally intercepted in imported fruit-tree scion wood. Illegal trafficking and insufficiently controlled exchange of plant material are the main pathways of PPV spread over long distances. For decades, since the first description of sharka in 1932, there has been neither public awareness nor reliable methods applicable on a large-scale. ELISA technique reported for plant viruses in 1977 revolutionized PPV diagnosis to its advantage. Nevertheless, for more than a decade, ELISA techniques have been based exclusively on polyclonal antibodies that often present problems of specificity and other drawbacks. The production and use of specific monoclonal antibodies and later recombinant antibodies, constituted the second revolutionary fact in PPV detection and characterization. An example of their usefulness is that about ten million ELISAs for universal PPV detection have been performed using 5B-IVIA/AMR since 1994. The emergence of molecular amplification methods revolutionized PPV detection, as well. The EPPO (2004) protocol for PPV is based on validated techniques and reagents. Nowadays, real-time RT-PCR techniques constitute the gold standard for PPV detection. Different formats including direct systems for sample preparation are included in the current IPPC-FAO (2012) protocol for PPV. The choice of the most appropriate detection method is crucial and must be related to the final goal or purpose of the analysis. The combination of ELISA-5B based and spot real-time RT-PCR techniques reaches 100% accuracy for PPV detection. "Next generation sequencing" is a powerful strategy for PPV detection and characterization and could be a potential substitute for biological indexing.