Potato Research Centre, Agriculture and Agri-Food Canada, 850 Lincoln Road, Fredericton, New Brunswick, E3B 4Z7, Canada.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Plant virus disease emergence, as defined by an increase in disease incidence, pathogenicity, and geographical or host range, may be mainly driven by virus introduction through trade in plant products, germplasm, seeds, rooted cuttings and live plants. Diversification, intensification, and globalization of agriculture also add to disease emergence. Re-emergence or further spread may occur due to the introduction of new vectors, recombination of different virus strains resulting in a more virulent strain, and the interaction of virus resistance genes in the evolution of aggressive strains. Among the new disease causing viruses worldwide, two plant virus families (Potyviridae and Geminiviridae) and one genus (Tospovirus) are well recognized. A case history of potato cultivation and spread of Potyvirus Potato virus Y (PVY) throughout the world illustrates the role of different factors in disease emergence. PVY strain groups have been based on host-response and resistance-gene interactions. The strain groups PVYO, PVYC and PVYN were well-established prior to 1980 for the isolates infecting field potatoes. A switch in the emphasis from host response to nucleotide sequence differences in the virus genome, detection of isolates recombining sequences of different strains, and the need to recognize isolates that cause necrotic symptoms in potato tubers have led to the recognition of new virulent sub-strains especially to the PVYN strain group in many countries.
