Viral Diseases in Potato

Viruses are among the most significant biotic constraints in potato production. In the century since the discovery of the first potato viruses we have learned more and more about these pathogens, and this has accelerated over the last decade with the advent of high-throughput sequencing in the study of plant virology. Most reviews of potato viruses have focused on temperate potato production systems of Europe and North America. However, potato production is rapidly expanding in tropical and subtropical agro-ecologies of the world in Asia and Africa, which present a unique set of problems for the crop and affect the way viruses can be managed. In this chapter we review the latest discoveries in potato virology as well as the changes in virus populations that have occurred over the last 50 years, with a particular focus on countries in the (sub-)tropics. We also review the different management approaches including use of resistance, seed systems, and cultural approaches that have been employed in different countries and reflect on what can be learnt from past research on potato viruses, and what can be expected in the future facing climate change. © The Editor(s) (if applicable) and The Author(s) 2020.Peer reviewe

Diversity, Characterisation and Classification of PVY

International audienceSince the discovery of PVY in the 1930s, many strain groups and vari-ants have been described although consensus on an agreed international nomencla-ture is still a matter of debate. The challenge for plant pathologists studying PVY remains to establish the biological significance of the genomic diversity of PVY arising from the new, diverse PVY populations and how it impacts on crop produc-tion in practice. The distribution and range of PVY variants identified over the years highlight the ongoing threat that PVY poses to solanaceous crops worldwide. While genome sequencing provides accurate information on the genomic structure of an isolate and has become the method of choice as a first step to studying the phylog-eny of novel isolates and their affiliation to a genotypic group, it is not a sufficient criterion to assign a PVY isolate to a specific strain group, as groups are identified by a defined set of reactions or symptoms that develop following infection of a range of potato cultivars harbouring known resistance genes and on tobacco plants. The purpose of this chapter is to give an update on the current status of knowledge of PVY diversity identified in different geographical regions and insights into iden-tification and classification of PVY variants

Detection and Diagnosis of PVY

International audienceThe worldwide prevalence of Potato virus Y (PVY) poses a continuous challenge to efficient potato production. The accurate diagnosis of viruses such as PVY is inherently challenging due to the broad biological and genetic diversity of PVY strains that elicit a range of symptoms and diseases in various potato cultivars and related solanaceous species. A wide range of techniques have been developed over a period of 50 years for the detection of PVY. Serological methods such as ELISA, using polyclonal and especially monoclonal antibodies, have been widely used by most diagnostic laboratories, due to their cost effectiveness and capacity to implement for a large number of samples. Over the last decade, PCR-based assays have been routinely used in diagnostic laboratories because of their sensitivity, specificity and their capacity to be automated for high-throughput testing. The objective of this chapter is to provide a brief historical overview of the main diag-nostic methods used to detect and identify PVY and to highlight those that are suit-able for either research or diagnostic purposes

Evolution and Origin of PVY

International audienceThe mechanisms by which Potato virus Y variants are generated and selected are still unclear. Spontaneous mutations generated by uncorrected replication error and recombination events between viral isolates during co-infection of plant cells are the main likely source of genetic diversity. This high level of diversity generation is essential for virus evolution and survival in different environments. Different PVY strain groups have appeared over time: firstly, non-recombinant PVYC, PVYO and PVYN strains and, more recently, recombinant PVYN-Wi and PVYNTN strains with novel biological characteristics and the ability to cause potato tuber necrotic ringspot disease (PTNRD). Increased fitness of the recombinant strains appears to have enabled them to replace the non-recombinant variants in most potato growing areas of the world. Partial sequencing of PVY genome (P1, HC-Pro, CP, recombinant junctions) and whole genome sequencing has shown that non-recombinant and recombinant variants are present in potatoes and other plant hosts. Phylogenetic analyses have been applied to document changes in viral isolates and to establish the relationships between different viral isolates. Traditional phylogenetic analysis was, however, developed for bifurcating phylogenies and not for analysing recombination, as a result of which this presents challenges to these analyses which will be outlined in this chapter. The ongoing worldwide studies on PVY characterisation suggest that new variants with distinct biological properties are likely to be uncovered in the future. Emerging technologies such as next generation sequencing will provide valuable insights into PVY population dynamics and evolution in future