Potato leafroll Virus
"The nature and severity of leafroll symptoms depend on the virus strain, potato variety, environment, and time and source of infection. Plants with chronic (seed tuberborne) infections are most severely affected. They typically are stunted and appear more erect. Lower leaves roll upwards at the margins, have a stiff leathery texture, and may die prematurely. In contrast, plants that become infected in the current season by aphid vectors of potato leafroll virus normally develop symptoms in the upper (youngest) leaves first; the leaves develop an upright orientation, become chlorotic, and roll upwards. Late-season infections are not always accompanied by symptoms. Potato leafroll virus can cause necrotic netting (net necrosis) in tuber vascular tissue of some varieties, including Russet Burbank."