Absence of Potato spindle tuber pospiviroid in Canada
As reported in EPPO RS 2003/077, surveys are being carried out in Canada to verify the absence of Potato spindle tuber pospiviroid (PSTVd - EPPO A2 List) from potato production. Occurrences of PSTVd were reported in the 1950s and a seed potato certification programme was initiated to eradicate it from Canada. Within this programme, all nuclear stock is tested by electrophoresis (rPAGE) to ensure freedom from PSTVd. Every year, seed potato fields are visually inspected (twice or more) for the presence of PSTVd and viruses. Symptoms of PSTVd have not been observed in the field for at least the last 25 years. In the provinces of Prince Edward Island and New Brunswick, PSTVd has been considered officially eradicated since 1989 on the basis of field inspections and tests (rPAGE and nucleic acid dot blot hybridization). More recently, surveys also confirmed its absence from Alberta, British Columbia and Saskatchewan. During 2000-2004, the PSTVd survey was extended to the provinces of Manitoba, Ontario, Québec, Nova Scotia and Newfoundland in which 211, 188, 95, 6 and 10 samples, respectively, were collected. Each sample consisted of 400 randomly selected leaves from selected potato fields (corresponding to seed lots at various stages of the certification scheme and to a few lots (11%) taken from commercial ware potato fields). All samples were tested by dot blot and a proportion of them (10%) were retested by rPAGE and northern blot. All test results were negative. Considering the cumulative results of the PSTVd surveys in all 10 Canadian provinces and the absence of the disease in the field, Canada declares that PSTVd is absent within its potato industry.
De Boer SH, DeHann TL (2005) Absence of potato spindle tuber viroid within the Canadian potato industry. Plant Disease 89(8), p 910.