Researchers identified three closely related plant viruses—Andean potato latent virus (APLV), dulcamara mottle virus (DMV), and Ononis yellow mosaic virus (OYMV)—that resemble turnip yellow mosaic virus. APLV was isolated from primitive potatoes in the tropical Andes, DMV from wild Solanum dulcamara plants in England, and OYMV from restharrow plants. All three viruses transmit readily by sap inoculation; APLV and DMV transmit through seeds, and DMV through the flea beetle Psylloides affinis. The viruses share similar properties: isometric particles 25-30 nm in diameter, two sedimentation components (115 S and 55 S), and nucleic acid with comparable base compositions (G 16%, A 22%, C 33%, U 29%). Serological tests confirmed their relatedness to each other but not to other known viruses tested. Plants infected with one virus showed no protection against the others. Chemical treatments with uracil analogs increased empty particle production relative to infectious particles.

Key findings

• Three closely related viruses with isometric 25-30 nm particles were identified, most similar to turnip yellow mosaic virus group
• All three viruses transmit by sap inoculation; APLV and DMV transmit through seed; DMV transmits via flea beetle vector Psylloides affinis
• Purified preparations contain two main particle types with sedimentation coefficients ~115 S (infectious nucleoprotein) and ~55 S (empty protein shells)
• The three viruses are serologically related to each other but show no serological relationship to turnip yellow mosaic, wild cucumber mosaic, cocoa yellow mosaic, squash mosaic, or red clover mottle viruses
• Cross-protection experiments showed no resistance between viruses—plants infected with one virus remain fully susceptible to the others