Wikipedia
Spraing
Spraing is a disease of potato tubers that causes brown streaks in the flesh of the potato. Spraing can be caused by two viruses, tobacco rattle virus (TRV) which is transmitted by trichodorid nematodes, or potato mop top virus (PMTV) transmitted by the powdery scab fungus Spongospora subterranea. The two viruses may have synergistic effects in disease progression when both are present.
Control of the disease is generally by ensuring that seed is disease free although the strain transmitted by nematodes can be controlled to some extent by the use of nematicides