Development of a serological assay for detecting serologically diverse banana streak virus isolates

Banana streak virus (BSV), a double-stranded DNA plant virus that belongs to the genus Badnavirus, causes banana streak disease. This disease occurs wherever bananas and plantains are grown. Symptoms include yellow and necrotic leaf streaks, lethal stem necrosis, pseudostem splitting and 'choking'. BSV is primarily disseminated in vegetatively propagated planting material such as corms, and tissue culture-derived plants. BSV is also seed transmitted, an important consideration in breeding programs. Successful management of BSV requires accurate detection of the virus to avoid the use of infected material for planting, tissue culture propagation, and breeding. Therefore, it is important to develop a reliable method for detecting the virus. However, BSV has high genomic and serologic variability which makes detection difficult. To obtain BSV specific broad spectrum polyclonal antibodies, rabbit and chicken polyclonal antibodies were prepared against sugarcane bacilliform virus (ScBV), a virus with close serological relationships to BSV. ScBV was isolated from a mixture of 32 sugarcane cultivars representing the widest serological diversity of this virus. In addition, polyclonal antibodies were generated to a BSV isolate from the banana cultivar 'Mysore', because this isolate is not serologically related to ScBV. Using the resulting polyclonal antibodies three of five serologically unrelated BSV isolates were detected using the double antibody sandwich enzyme immunoassay (DAS-EIA). However, immunosorbent electron microscopy showed that all five tissue samples tested in the DAS-EIA had virus particles. The five BSV isolates were detected using the triple antibody sandwich enzyme immunoassay (TAS-EIA). These results indicate that TAS-EIA is more sensitive and more likely than DAS-EIA to detect a wider range of BSV isolates in infected banana and plantain material using the polyclonal antibodies produced.