Abstract
Particles of tobacco necrotic dwarf (TNDV) and potato leafroll (PLRV) viruses, both of which are phloem-limited and transmitted by aphids in the persistent manner, contain a single-stranded RNA of mol. wt. 2.0 x 106, estimated from their mobilities in polyacrylamide gel electrophoresis. The results suggest that both viruses belong to the group of luteoviruses. TNDV has two minor RNA components of mol. wt. approx. 1 x 105.