Molecular characterization and interviral relationships of a flexuous filamentous virus causing mosaic disease of sugarcane (Saccharum officinarum L.) in India

A virus isolate causing mosaic disease of commercial sugarcane was purified to homogeneity. Electron microscopy revealed flexuous filamentous virus pa rticles of ca 890 x 15 nm. The virus isolate reacted positively with hetero logous antiserum to narcissus latent virus form UK, but failed to react wit h potyvirus group specific antiserum. N-terminal sequencing of the intact c oat protein (CP) and the tryptic peptides indicated that the virus was prob ably a potyvirus but distinct from several reported potyviruses. Comparison of the 3'-terminal 1084 nucleotide sequence of the RNA genome of this viru s revealed 93.6% sequence identity in the coat protein coding region with t he recently described sugarcane streak mosaic virus (Pakistani isolate). Th e molecular weight of the coat protein (40 kDa) was higher than that deduce d from the amino acid sequence (34 kDa). The apparent increase in size was shown to be due to glycosylation of the coat protein which has not been rep orted thus far in the family, Potyviridae. This is the first report on the molecular characterization of a virus causing mosaic disease of sugarcane i n India and the results demonstrate that the virus is a strain of sugarcane streak mosaic virus, a member of the Tritimovirus genus of the Potyviridae . We have named it sugarcane streak mosaic virus - Andhra Pradesh isolate ( SCSMV-AP).