Molecular cloning, sequencing, and phylogenetic relationships of a new potyvirus: Sugarcane streak mosaic virus, and a reevaluation of the classification of the Potyviridae

The nucleic acid of a serologically distinct potyvirus, originally isolated out of sugar cane from Pakistan, was reverse transcribed and the 3' termin al 2000 bp was PCR amplified, cloned, and sequenced. Phylogenetic compariso ns of viruses representing each genus of the Potyviridae show that the Paki stani isolate is most closely related to the rymoviruses wheat streak mosai c virus (WSMV) and brome streak mosaic virus. We therefore propose that thi s new virus species be named sugar cane streak mosaic virus to reflect its similarity to WSMV. The phylogenetic data also show that the genus Rymoviru s contains at least two unique evolutionary lineages. Thus the current taxo nomy, based on transmission vector, is paraphyletic. We present an analysis of the taxonomic relationships among members of the family and propose a c lassification that both resolves the paraphyly and more accurately represen ts the evolutionary history of the Potyviridae. (C) 1998 Academic Press.