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Potato Y virus | AG1196 |
Jane Moran and Brendan Rodoni, Knoxfield
July 2003 |  |
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This Agriculture Note describes Potato virus Y in potatoes.
Potato virus Y (PVY) is found worldwide, and is widespread but uncommon in most parts of Australia. It infects potato and a number of other solanaceous crops such as tomato and capsicum and weeds such as species of nightshade. In potatoes, it is particularly important in seed crops, because it can be passed on to successive crops in seed tubers.
There are a number of strains of PVY known, and most strains are likely to occur in Australia. The most common is the ‘O’ strain (PVYO ), and this does not appear to produce disease symptoms in Australia. PVYO occurs worldwide, PVYC occurs in Australia, Ecuador, New Zealand, Europe, South Africa and N. America, PVYN is found in North America, New Zealand, Europe, Africa and S. America and has been reported in tobacco in Australia.
A new strain of PVY designated PVYNTN, was first described in Europe in 1980 and has since been found in the USA, the Middle East and Japan. This strain is becoming more frequent in the UK. The closely related strain, PVYN has been the subject of eradication campaigns in New Zealand and Canada. PVYN is also not known to occur in potatoes in Australia, although surveys have only recently been initiated because no widespread disease symptoms have been observed.
Symptoms
PVY symptoms can differ according to the potato variety, the strain of the virus present and environmental conditions during growth and in storage. They range from severe to symptomless. Cultivars react differently to infection. Symptoms in growing plants vary from very mild to severe yellow mottling on the leaves. Tubers mostly show no symptoms, however some potato varieties under certain conditions may exhibit tuber necrosis (Fig. 1).
Potato plants
Leaves may be mottled, yellow or have dead patches. The dead areas usually start as patches or rings on the leaflets and then grow to affect the entire leaflet. The leaflet collapses and may drop from the plant or remain attached. In addition to the mottling, severe rugose wrinkling may occur. Brown streaks may also occur on the veins, the petioles and down the stem.
Plants grown from infected tubers may be stunted and have mottled, crinkled leaves. Generally, the yellow-green mottling is of a very fine pattern. The leaves and stems occasionally die. Some infected plants remain symptomless.
Potato tubers
In most instances, no tuber symptoms are produced, and only a slight reduction in tuber size may occur. However certain strains of the virus can cause tuber symptoms in some cultivars. In the UK, the cultivar Nadine is susceptible.
Superficial necrotic ring spots (tuber necrosis) may occur on infected tubers and this may render the crop unfit for marketing (Fig. 1). The development of tuber necrosis is dependent on warm temperatures in the latter stages of growth in the field and during storage. Tubers may be infected but no symptoms develop because environmental conditions are not favourable or because the cultivar is tolerant.
Figure 1. Tubers showing superficial ringspots.
Economic damage
By reducing tuber size, PVY reduces the total yield of a crop. Tuber necrosis caused by the virus can affect crop quality and further reduce marketable yield.
Spread and source of infection
Note: Organisms, which are responsible for spreading a disease, are known as vectors of the disease.
PVY is spread in potato crops by planting infected tubers and by many species of aphids.
Propagation
PVY can be carried from one potato crop to the next through use of infected seed.
Aphids
Many species of aphids are able to transmit PVY, and one of the most effective vectors is green peach aphid, Myzus persicae. Aphids only need to feed on an infected plant for a very short time, as little as 20 seconds, to become infected with the virus. If an infected aphid feeds for a similar time on a healthy plant it can infect it. Consequently the use of insecticides to control aphids may not eliminate transmission.
The most likely sources of both aphids and PVY in Victoria are volunteer potatoes and solanaceous weeds such as black nightshade.
Management
Virus diseases such as PVY cannot be cured, but measures can be taken to manage them.
The single most important control strategy is the use of Certified Seed. If accompanied with weed control in and around crops and good control of volunteer potatoes, it is possible to have excellent control of this virus.
Further information
If PVY is suspected in a potato crop, contact Crop Health Services on (03) 9210 9356 for further information.
The advice provided in this publication is intended as a source of information only. Always read the label before using any of the products mentioned. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication.
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