A ProMED-mail post
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Date: Tue 25 Jan 2011
Source: Times-News [edited]
New potato virus strain has industry on edge
A potato virus, around for years, is mutating. Growers have grown used to seeing some signs of _Potato Virus Y_, or PVY, in fields. The disease causes foliar damage and infected plants must be taken out of certified seed fields, but otherwise the virus hasn't really been a threat.
That could be changing. Researchers are finding new strains of the virus damaging tubers with little apparent injury to an infected plant's leaves. When specialists in the US surveyed PVY strains between 2004 and 2006, they found 70 percent were the ordinary PVY that causes leaf damage but not tuber damage.
By 2010, surveys showed tuber necrotic strains are increasing in both incidence and distribution, said Stewart Gray, Agricultural Research Service New York. Tuber necrotic strains accounted for 18 percent, up from 6 percent previously, and ordinary strains had fallen to 53 percent. "This is no longer just a seed certification problem. The problem now affects all aspects of potato production," he said.
The primary concern is that PVY will become a major quality disease as it did in Europe in the 1980s. [Some] potato varieties can no longer be planted there because of PVY, highly susceptible varieties could be lost. As the strains change to more of the necrotic type, commercial growers will have to pay more attention to PVY.
Infected plants that do not show much foliar or tuber damage, can still be affected by PVY. "A good looking crop in the field does not translate into disease-free tubers," Gray said. He emphasizes removing infected plants and planting healthy tubers, but the shift in PVY strains is creating challenges for certified growers as well.
[Byline: Cindy Snyder]
[[_Potato Virus Y_ (PVY; type member of genus _Potyvirus_) is one of the most damaging potato viruses affecting crop yields and tuber quality. PVY can also affect tomato, capsicum, and some other related species. Symptoms vary depending on viral strains and susceptibility level of host cultivar. They may include mottling, distortion and necrosis of leaves and stems, premature defoliation, tuber necrosis and plant death, or no symptoms at all.
PVY is transmitted by aphids in a non-persistent manner, with _Myzus persicae_ being the most efficient vector. PVY can also be spread by mechanical means, plant-to-plant contact, or with infected planting material such as seed tubers. Disease management of PVY and other potato viruses relies largely on clean planting material and use of resistant crop varieties, but reduction of available virus reservoirs and vector numbers may also be useful.
The emergence of new PVY strains has recently been reported from different areas (see ProMED-mail posts listed below). Numbers of co-infecting strains will build up with every crop cycle if PVY infected seed tubers are used, especially if these are moved to different areas where the virus strains they carry may combine with local PVY populations.
PVY symptoms on potato:
PVY particles, electron micrograph:
Aphid vector _Myzus persicae_:
Information on _Potato virus Y_:
Information on PVY and other potato viruses:
Review and diagnosis of PVY strains:
PVY taxonomy and description:
Potato virus Y - Australia: update 20100329.0984 Potato viruses - Canada: (PE) 20100125.0273
Potato virus Y - South Africa: new strain, spread 20091111.3913 Potato virus Y - Switzerland: new strains 20090703.2396 Viruses & nematodes, potato - UK: alert 20090212.0628
Potato virus Y, necrotic strain - USA (north west) 20021001.5434
Potato viruses - Saudi Arabia 19970414.0796 Aphis gossypii: new potato virus vector? - UK 19970113.0059]