The role of volunteer potatoes in the spread of potato virus YN in ware crops of cv. Record

摘要

Surveys were made for the presence of potato Y potyvirus (PYV) in planted seed and harvested tubers in ware potato crops of cv. Record grown at 3 sites in England in 1994 (survey 1) and 7 sites in 1995 (survey 2). PYV was not found in samples of planted seed, but high levels of infection were found in many, but not all, harvested crops. However, plants of volunteer potatoes (VP) (i.e. plants arising from tubers or true seed derived from previous crops and surviving in soil) were frequently found tobe infected. Infection in tubers harvested from crops in the 1st survey ranged from 2 to 52%. In 1995, VP were collected from 2 of the 3 English sites where potato crops had been grown the previous season and also from a site in Scotland where PYV infection in an experimental crop of cv. Record had been monitored in 1994. The percentages of infected VP ranged from 2 to 54%. PYVN was the predominant strain found in sampled VP, with only 2 plants (out of 300 infected) containing PYVO. In the 2nd survey,VP were assessed within the 1995 ware crops and were found at 4 sites, at which they comprised between 4 and 8% of emerged potato plants. Between 31 and 93% of VP were infected. Again, PYVN was the predominant strain with one plant containing PYVO and another PYVC (out of 189 infected). A sample of harvested tubers from each site was also tested for PYV. At those sites which had many infected VP, the harvested crop contained a large percentage of infected tubers, ranging from 60 to 97%. Two sites whichhad not previously been used for cropping potatoes had no VP and a very low incidence of PYV infection in the harvested tubers (1 and 2%). However, although no VP were found at one site, 31% of harvested tubers were infected, suggesting that alternativeinoculum sources may be important.