Symptoms on foliage

Depending on the virus strain and the potato cultivar, PVM symptoms range from very mild to severe: mottle, mosaic pattern, crinkling and rolling leaves and possibly associated with stunted shoots.

Typical symptoms of PVM have been called paracrinkle or potato leaf rolling mosaic as they have the appearance of rolling in the top of the plants (photo 1) with mild mosaic and ”spoon-shaped” rolled leaflets. Leaf rolling due to PVM is soft when touched whereas Potato leaf roll virus induces a «cracking» leaf rolling. It occurs in developed plants, usually on the top leaflets.

With some cultivars, the following symptoms may also be observed (photos 2 et 3):

• deformed leaflets;
• slight discolouration of the veins in the top leaves;
• waviness on the edges of the leaves;
• leaf mosaic symptoms (photo 2).

Symptoms are more visible with cloudy and temperate weather.