Characterization and expression of the coat protein-coding region of banana bract mosaic potyvirus, development of diagnostic assays and detection of the virus in banana plants from five countries in southeast Asia

Summary.

 We have sequenced the entire coat protein (CP)-coding region and 5′ 162 nucleotides of the 3′ untranslated region (UTR) of nine different isolates of banana bract mosaic virus (BBrMV) from five different countries. Further, we have sequenced the 3′ 621 nucleotides of the NIb-coding region of a Philippines isolate. This is the first report of BBrMV in Thailand, Vietnam and Western Samoa. When the sequences of the CP-coding region and 3′ UTR were compared to each other, variability of between 0.3% and 5.6%, and 0.3% and 4.3%, was observed at the nucleotide and amino acid levels, respectively. Phylogenetic analysis of the BBrMV isolates did not reveal any relationship between the geographic location of the isolates. The BBrMV CP was expressed in Escherichia coli as a fusion protein and the purified recombinant protein was used to produce a high titre BBrMV-specific polyclonal antiserum. This antiserum was used to develop a F(ab′)₂ indirect double antibody sandwich ELISA and compared with immuno-capture PCR (IC-PCR) and reverse transcription PCR (RT-PCR) assays for BBrMV detection. RT-PCR was shown to be the most sensitive test followed by ELISA and IC-PCR.