Abstract:
The causative agent of banana streak disease (BSD) is Banana streak virus (BSV). In tropical
countries such as Kenya, the virus causes considerable damage to the banana crop besides lowering
banana production yields. Several mealy-bug species have been reported as vectors of BSV. The
latent and retention time of the BSV in the oleander mealy-bug (Paracoccus burnerae) is however
unknown. The latent and retention times of viruses in disease vectors are important characteristics in
the determination of the mode of transmission of viruses by their vectors. The purpose of this study
was to determine the latent and retention time of the BSV in its vector, P. burnerae. We employed
both the Immuno-capture Polymerase Chain Reaction (IC-PCR) and Rolling Circle Amplification
(RCA) techniques to select diseased and healthy plantlets for transmission trials. RCA assays were
performed on the deoxyribonucleic acid (DNA) samples of viruliferous mealy-bug instars of P.
burnerae and on the DNA of virus-inoculated plantlets. The findings of the study indicated that BSV
has no latent period in P. burnerae during transmission at ambient conditions (9-30°C). However, the
vector can retain and transmit BSV for a period of four days under ambient temperatures (9-30°). The
results revealed that the vector P. burnerae, transmits BSV semi-persistently which is an indication of
a non-circulative mode of transmission of the virus. The results of this study contribute to the
elucidation of the mode of transmission of BSV by P. burnerae and impetus for the development of
novel control strategies of BSD. Further studies are recommended to determine the specific BSV and
vector proteins involved in the transmission process. Such studies have the potential to contribute to
development of novel disease management strategies based on the use of viral genes that encode for
proteins that are defective to prevent vector inoculation and successful transmission of BSV by its
vectors. From our results, we also recommend further screening studies for banana plant encoding
molecules (e.g. peptides) that are able to bind to cuticle protein receptors in the vector mouthparts
which may provide innovative virus management strategies by interfering with the process of virus
retention.
