SEQUENCE-ANALYSIS OF THE GENOMIC RNA 3'-TERMINAL REGION OF A POTYVIRUS FROM BRACHIARIA SPP RELATED TO GUINEAGRASS MOSAIC-VIRUS

The 3' terminal region of the genomic RNA of a potyvirus isolated from Brachiaria spp. which is related to guinea grass mosaic virus (GGMV), was compared to that of members of the sugarcane mosaic subgroup of p otyviruses. Reverse transcription-polymerase chain reaction (RT-PCR) o f total nucleic acid extracted from infected B. brizantha resulted in the amplification of a DNA product of c. 0.9 kb. This product was clon ed and sequenced; it has an open reading frame of 149 amino acid resid ues, and a 3' untranslated region (UTR) of 474 nucleotides. Optimal al ignments of the 3' UTRs of the Brachiaria potyvirus and members of the sugarcane mosaic subgroup of potyviruses showed that it has nucleotid e sequence similarities of c. 42, 46, 46, and 46% to maize dwarf mosai c virus strain A, sugarcane mosaic virus strains SC and MDB, and sorgh um mosaic virus strain SCH, respectively. It had higher nucleotide seq uence similarities of c. 88, 89, and 92% with Johnsongrass mosaic viru s (JGMV) strains MDO, MDKS1 and JG, respectively. Analyses of the dedu ced amino acid sequence of the Brachiaria potyvirus coat protein fragm ent revealed a 97.3% similarity to the JG strain of JGMV to which it i s serologically related. We propose that the Brachiaria potyvirus now be considered a strain of JGMV (designated JGMV-Brac).