Disease Resistance and Pathology

Sunflower plants showing chlorotic ring spot symptoms were observed during the 2005/2006 crop season in the southeast of the Province of Buenos Aires in Argentina. Preliminary studies, including host range symptoms, serological tests and electron microscopy, had identified this virus isolate as a potyvirus closely related to Sunflower chlorotic mottle virus (SuCMoV). The nucleotide sequence of the genomic 3 ́ terminal region of this potyvirus was determined and characterized. The sequence consisted of 1304 nucleotides (nt) includingthe C-terminal region of the nuclear inclusion b protein gene (NIb), the capsid protein gene (CP) and the 3 ́non-coding region (3 ́-NCR). The partial putative NIb gene (240 nt) encoded a protein of 80 amino acids (aa) residues and the CP gene (807 nt) encoded a protein of 269 aa residues. The 3 ́-NCR was 257 nt in length excluding the poly (A) tract. Sequence comparisons of the predicted CP aa and 3 ́-NCR were analyzed separately in order to determine the relationship between this potyvirus and SuCMoV, and other reported potyviruses. The CP of this potyvirus isolated from sunflower shared 94.8% aa identity with SuCMoV (Argentina) and 89.2% with SuCMoV-Zi (Brazil). The 3 ́-NCR shared 94.2% nt sequence identity with SuCMoV. These data indicate that the potyvirus causing chlorotic ring spot (CRS) symptoms in sunflower is closely related to SuCMoV and it is provisionally referred to as SuCMoV strain CRS.