Non-confirmation of banana bunchy top virus in South Africa

Following a recent report (Su, H. J <i>et al</i>. (1992) In: <i>Proceedings: International symposium on recent developments in banana cultivation technology</i>, pp. 309-313) of banana bunchy top nanavirus (BBTV) on bananas in South Africa based on ELISA, an investigation was conducted to confirm the diagnosis and to assess the extent of the disease. Various ELISA protocols, immuno-EM (IEM) and polymerase chain reaction (PCR) amplification were used to test for the presence of BBTV. Samples were collected during 3 seasons from the site on which the first report was based. No plants with typical BBTV symptoms were seen and BBTV was not detected in any of the samples tested. It was demonstrated that the BBTV ELISA system used during the first report was prone to false positive reactions, as confirmed by other ELISA protocols using the same and other antisera, IEM and PCR tests. The first report of this virus in South Africa was apparently based on such false positive ELISA reactions. South Africa must still be considered free of BBTV and phytosanitary legislation and vigilance by the local banana industry needs to be maintained