APS Homepage

POSTERS: New and emerging diseases

Identification of Cycas necrotic stunt virus (CNSV) in alfalfa (Medicago sativa)
Peng Jiang - USDA/ARS. Lev Nemchinov- USDA ARS MPPL

Cycas necrotic stunt virus (CNSV), genus Nepovirus, family Secoviridae, was first detected in the gymnosperm Cycas revoluta in Japan. Prior to this report, it has not been identified in alfalfa (Medicago sativa L.). While analyzing alfalfa transcriptome datasets generated by others (SRR7751381, SRR7751384, SRR7751386), we found a total of 4,209 reads of CNSV that were subsequently assembled into an essentially complete viral genome. The virus has a bipartite single-stranded positive sense RNA genome; RNA1 and RNA2 are of 6,891 and 4,196 nucleotides in length, respectively. RNA1 encodes polyprotein 1 (P1) with predicted motifs for a protease cofactor, an NTP-binding domain, viral genome-linked protein, a cysteine protease, and a RNA-dependent RNA polymerase; RNA 2 encodes polyprotein 2 (P2) with predicted domains for a movement protein and a coat protein. P1 consists of 2020 amino acids (aa) and shows 96.3% overall identity to the P1 of CNSV (AEN25475) while the P2 is 1260 aa-long and has 93.4% overall identity to the P2 of CNSV (AEN25476). The Pfam-predicted coat protein (CP) region of P2 shared ~ 97.8% identity with the CP of CNSV (NP620620) and pfam-predicted RNA dependent RNA polymerase (RdRP) region showed 93.9% identity to the RdRP of CNSV (NP620619). Based on these observations, the virus represents a new strain of CNSV adapted to Medicago sativa, for which we propose the name CNSV-A.