Potato Mop Top Symptoms on Leaves and Stems

Foliar and stem symptoms develop only on plants growing from infected seed. Because infected seed does not transmit the disease to all of the plant stems, only the
leaves from infected stems will show potato mop top symptoms. The systemic infection of the virus is erratic:

infected stems may have some healthy leaves, or infected leaves may have some healthy leaflets.
Foliar symptoms are highly variable and may appear as yellow blotches (aucuba pattern), V-shaped yellow chevrons,“thistle leaf ” patterns around the veins,
deformed leaves, wavy or rolled margins, and bunching of foliage.

Infected stems are shortened at the internodes, resulting in stunted plants with bunched foliage.
The overall effect is a dwarfed and bunched growth habit.
The name mop top refers to this growth habit.