Serological and coat protein sequence studies suggest that necrosis disease on sunflower in India is caused by a strain of Tobacco streak ilarvirus

Summary.  Serological and coat protein sequence studies were conducted to identify an ilarvirus associated with necrosis disease on sunflower in India. In electroblot immunoassay, sunflower ilarvirus reacted strongly only with antiserum to Tobacco streak virus (TSV). The coat protein gene of sunflower ilarvirus was cloned and sequenced. The sequence analyses also showed that the CP gene was most closely related to TSV, the member of subgroup I of Ilarvirus. The sunflower ilarvirus CP shared 90% amino acid sequence identity with TSV. On the basis of serological relatedness and sequence identity, it is proposed that the sunflower ilarvirus from India should be considered a strain of TSV belonging to subgroup I and designated as TSV-SF. This is the first report of the molecular characterization of TSV on sunflower from the Indian subcontinent. Received August 9, 2001 Accepted October 11, 2001