Symptoms on foliage

On the majority of potato cultivars, PVS causes few or no symptoms, especially for PVS^O strains which usually are symptomless (latency) or cause mild symptoms, which vary according to the cultivar and the viral strain:

• lightening of the foliage (slight chlorosis);
• deepening of the veins on the upper side of the leaves (rough to the touch, rugosity) (photo 1);
• smaller leaf size;
• undulation of the margin;
• tips of the leaflets inclined downwards (photo 2).

In highly susceptible cultivars, the symptoms are more pronounced, with a bronzed appearance, necrotic spots and smaller plants. 

PVS^A has been reported to cause more severe symptoms.