PURIFICATION, PROPERTIES, AND DIAGNOSIS OF BANANA BRACT MOSAIC POTYVIRUS AND ITS DISTINCTION FROM ABACA MOSAIC POTYVIRUS

Using biochemical, serological, and cytopathological evidence, we have confirmed that banana bract mosaic virus (BBrMV) is a distinct member of the family Potyviridae. Virions of a Philippine isolate of BBrMV w ere purified from field-infected banana cv. Cardaba. Particles were ap proximately 725-nm long, banded at a density equivalent to 1.29 to 1.3 1 g/ml in cesium chloride equilibrium gradients, and had an A(260/280) of 1.17. Yields of about 4 mg/kg were obtained from fresh or frozen l eaf midrib or lamina tissue. Three major protein species with sizes of 31, 37, and 39 kDa were resolved from dissociated virions, and all re acted specifically with polyclonal antibodies to BBrMV. Infected leaf cells contained typical pinwheel inclusions. Virus-specific cDNA was a mplified from field samples by reverse transcription-polymerase chain reaction (RT-PCR) assay using potyvirus degenerate primers. In plate-t rapped antigen-enzyme-linked immunosorbent assay (ELISA), weak serolog ical relationships were demonstrated between BBrMV and other members o f the family Potyviridae, including abaca mosaic (AbaMV), dasheen mosa ic, maize dwarf mosaic, sorghum mosaic, sugarcane mosaic, and wheat st reak mosaic viruses. Despite similarities in the symptoms caused by th e two viruses, AbaMV was serologically distinct from BBrMV and reacted only weakly, or not at all, with BBrMV antibodies in double-antibody sandwich (DAS)-ELISA. No cross reactions were observed when RT-PCR pro ducts from the two viruses were examined by Southern blot hybridizatio n using BBrMV- and AbaMV-specific digoxigenin-labeled DNA probes. BBrM V was consistently associated with banana bract mosaic disease, as ass essed by DAS-ELISA and Southern blot hybridization using DNA probes. T he known geographical distribution of BBrMV was extended to include In dia (Kokkan disease) and Sri Lanka.