Banana bract mosaic virus: characterisation using potyvirus specific degenerate PCR primers

Banana bract mosaic (BBMV) is a relatively new, non-persistently aphid transmitted disease of bananas in the Philippines. Partially purified preparations from infected plants contained low numbers of flexuous virions, 660 to 760 nm in length, and a 38kDa protein, possibly the coat protein, which reacted with a general potyvirus antiserum in western blots. There were insufficient virions for conventional antiserum production or cDNA synthesis. Therefore, DNA was amplified using potyvirus-specific degenerate primers and reverse transcriptase PCR. The PCR products were cloned, sequenced and analysed and contained a 5' open reading frame of up to 150 amino acids and a 3' untranslated region of up to 190 nucleotides which were clearly related to the C-terminal half of the coat proteins and the 3' untranslated regions, respectively of potyviruses. The BBMV open reading frame amino acid sequence was most similar to the C-terminal half of the maize dwarf mosaic potyvirus coat protein (71.3% similarity) and the BBMV 3' untranslated region was most similar to that of ornithogalum mosaic potyvirus (39.6% similarity). Our results show that BBMV is a distinct potyvirus and also demonstrate the application of virus group specific primers in the characterisation of previously undescribed viruses.