Symptoms

• Symptoms on foliage

PVY^NTN isolates cause mosaic patterns and crinkling of varying intensity in the foliage, similar to the symptoms caused by PVY^O isolates.

With primary infections (i.e. occurring during the current year), other symptoms may be found:

• necrotic spots on the leaves (photo 1);
• vein necrosis mainly seen on the underside of the leaves;
• necrotic streaks on the stems (photo 2) and the petioles or oak-leaf-shaped leaf necrosis (photo 3);
• yellowing with the presence of green rings or particular patterns (“Maritta-type” symptoms: photo 4).

• Symptoms on tuber

• brown blisters in the form of arcs, rings or lines, caused by PVY^NTN (photo 5);
• necrotic arcs and rings: a symptom often caused by a primary PVY^NTN Infection (photos 6 and 7).

These necrotic tissues then become depressed and may even crack. However, they remain limited to the periderm (photo 8).