Potato virus Y
Causative agent and transmission
The virus Y is a Potyvirus transmitted by numerous species of aphid. It is a non-persistent type virus because the aphid can only transmit within a period of two hours after having been itself contaminated. The initial contamination of the aphid arises from a previous attack on another plant.
The initial inoculum for contamination can come from diseased plants in the plot or nearby, from infected regrowth or other host plants (tomatoes, tobacco, etc.).
Description of the symptoms
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The appearance of symptoms on a crop depends on the strain of virus Y (Yo: ordinary Y or Yn: necrotic), the variety, the weather conditions and the type of infection (primary or secondary).
In the case of strains of type Yo, contamination during the current year (primary infection) emerges through the appearance of black necrotic blemishes, on the veins and the undersides of leaves. The leaves become brittle and dry, while remaining attached to the plant. It can also produce a distorting mosaic (crinkle), often located on a stem or part of the plant.
On the other hand, contamination during the previous year (secondary infection) produces much more pronounced symptoms, which are highly variable according to the variety. They comprise three types:
• crinkle: deformation of the leaves with mosaic, or in an embossed pattern together with the appearance of a glossy and mosaic effect,
• mottle: dwarfism with large necrotic blemishes on the foliage ribs and with substantial distortion of the plants,
• mosaic (alternating pale green and dark green areas) non-distorting, but more or less obvious according to the variety and more visible in cloudy weather.
In the case of the virus Yn, the infection in the current year produces weak mosaics, while infection in the previous year gives more or less marked mosaic symptoms.
- The use of healthy seed potatoes resulting from genealogical selection;
- Production in a favourable environment;
- Roguing of virus-infected plants;
- Haulm defoliation before maturity;
- Treatment with mineral oils.