|Shiel, P - UNIVERSITY OF IDAHO|
|Freeman, T - NDSU|
|Isakeit, T - TEXAS A&M UNIV|
|Berger, P - UNIVERSITY OF IDAHO|
Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 18, 2002
Publication Date: N/A
Interpretive Summary: Virus diseases of sunflower in North America are practically non-existent, with only 3 published records in the past twenty years. One of those was in a research plot in Beltsville, MD and the other two cases were on wild sunflowers in Texas. In 1999, wild sunflower in the Rio Grande valley of Texas were noticed with mosaic symptoms, and these leaves contained long, rod shaped structures in their sap when viewed under an electron microscope. Two years of extensive work by USDA and university scientists in North Dakota, Idaho and Maryland resulted in a thorough characterization of the virus causing these symptoms (termed sunflower mosaic virus). The virus is a member of the "potato Y" virus group, it causes symptoms only on sunflower, other Helianthus species and zinnia, and is transmitted.
Technical Abstract: Sunflower mosaic is caused by a putative member of the Potyviridae. Sunflower mosaic virus (SuMV) was characterized in terms of host range, physical and biological characteristics, and nucleotide and amino acid sequence. Infected cells show cytoplasmic inclusion bodies, typical of potyviruses, when examined by electron microscopy. The mean length of purified particles is about 723 nm. Of 74 genera tested, only species in Helianthus, Sanvitalia, and Zinnia, all Asteraceae, were systemic hosts. Commercial sunflower hybrids from the United States, Europe and South Africa were all equally susceptible. The virus can be transmitted by Myzus persicae and Capitphorus elaegni. The virus was also seedborne in at least one sunflower cultivar. Indirect-ELISA tests with a broad-spectrum potyvirus monoclonal antibody were strongly positive. SuMV-specific polyclonal antisera recognized SuMV and, to a lesser extent, Tobacco etch virus (TEV). Indirect ELISA results with polyclonal antisera indicate that virus titer in three sunflower varieties remains low, whereas virus accumulates to much higher levels in two zinnia varieties tested. When tested against a panel of 31 potyvirus-differentiating monoclonal antibodies, SuMV was shown to be distinct from any potyvirus previously tested. SuMV shared four epitopes with TEV, but evidenced a reaction profile more similar to tulip breaking virus (TBV). SuMV did not possess epitopes unique only to TBV. Analysis of the predicted coat protein indicated a molecular weight of 30.5 kDa. The 3'-end of the virus' genome was cloned and sequenced. On the basis of coat protein amino acid sequence phylogenetic analysis, SuMV is a distinct species within the Potyviridae, with TEV being the virus species most closely related to SuMV.