Etiological Distinctions Between Tomato Yellow Top Virus and Potato Leafroll and Beet Western Yellows Viruses. Sher Hassan, Graduate Student, Department of Plant Pathology, Washington State University, Pullman 99164. P. E. Thomas, Research Plant Pathologist, USDA, ARS, Irrigated Agriculture Research and Extension Center, Prosser 99350. Plant Dis. 68:684-685. Accepted for publication 30 January 1984. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1984. DOI: 10.1094/PD-68-684.

Tomato yellow top virus (TYTV) is serologically related to potato leafroll (PLRV) and beet western yellows (BWYV) viruses. Tests were performed to determine whether the etiology of TYT disease was the same as that of PLR or BWY diseases in tomatoes, potatoes, and sugar beets. In August, TYTV-infected tomato plants occurred sparsely and were distributed at random in a field adjacent to a plot of potatoes chronically infected with PLRV. In contrast, a high incidence of PLRV was detected in symptomless tomato plants in the row adjacent to the potato plot. The distribution and incidence of TYT-diseased plants throughout the field adjacent to PLRV-diseased potatoes was similar to that found in a field 300 m away. Sugar beets were grown between rows of tomatoes that contained about 50% TYTV-infected tomato plants by the end of the season. Among 500 sugar beets tested, none were infected with a virus transmissible to Physalis floridana, a common host of the three viruses. Therefore, the etiology for TYT was distinct from that of PLR or BWY diseases despite serological relationships between the causal viruses. Although potatoes are not involved in the epidemiology of TYTV at present, the virus infects potato and could become prevalent in potatoes because it produces mild symptoms in this host. Thus, it could have an important economic impact on both tomato and potato production.