Movement and transmission of banana bunchy top virus DNA component one in bananas

The systemic movement and replication of banana bunchy top virus (BBTV) DNA component one were investigated. Strand-specific RNA probes and PCR were used to indicate the presence of the virus in various parts of infected banana plants during infection on the basis of dsDNA replicative intermediates of BBTV. The strand-specific probes were not only able to detect the presence of the virus but also gave an indication of where the virus replicated. The results using both the virion sense and complementary to virion sense specific probes were essentially the same indicating that BBTV initially replicated for a short period at the site of inoculation, and subsequently moved down the pseudostem to the basal meristematic region and ultimately into the roots and newly formed leaves. The virus was detected in the leaves formed prior to inoculation after 21 days using PCR but was not detected by the RNA probes. This indicated that the virus had the ability to move into these leaves but may not have replicated or accumulated to significant levels. The appearance of multimeric forms of BBTV suggested that the virus may have replicated via a rolling circle mechanism. Additionally, BBTV DNA component one did not appear to replicate in its aphid vector, Pentalonia nigronervosa.