Abstract:
Banana is an important crop in East Africa. In the tropics, banana and plantains are a major source of carbohydrate for about 400 million people of whom 200 million are from East Africa. In Kenya, the banana serves both as a subsistence crop as well as a cash crop. The production of banana in Kenya is however constrained by viral diseases especially the Banana Streak Disease (BSD) which is caused by the Banana Streak Virus (BSV). Breeding between A and B-genomes containing banana have been significantly constrained by BSV due to activation of the integrated viral sequences in the genome of the interspecific hybrids. The episomal DNA viral particles are thought to be transmitted by several mealy-bug species but there are no reports on the transmission of the BSV by other viral insect vectors. This study aimed at elucidating the mode of transmission of BSV by mealy-bug species in Kenya and identifying any other putative vectors of BSV in samples collected from infected banana plantations. The mealy-bugs were reared on pumpkin fruits in black cages and were used in the virus transmission cycle experiments. The instars of the Paracoccus burnerae (mealybug) species were fed on BSV infected plants to acquire the virus and on the healthy plantlets for inoculation. The effect of the acquisition period on the transmission of the BSV, the latent period and the retention period of the BSV by the mealy-bug species were determined using Rolling Circle Amplification (RCA). In addition, leafhoppers and banana aphids collected from the infected banana plantations were assayed for the presence of BSV using RCA. RCA products were assayed by electrophoretic analysis. Principal characteristics of the modes of
Virus transmission by insects were used to conclude the mode of transmission of the BSV by mealy-bugs. Results from this study revealed that the P. burnerae is able to acquire the virus and transmit it after a minimum of six hours of acquisition access time. The virus had no latent period in the vector though it could be retained in the vector for four days after acquisition feeding, characteristics of semi-persistent mode of transmission. In addition, the results revealed that Banana aphids and leafhoppers are not potential vectors of BSV. Viruliferous mealy-bugs should be reduced by destroying BSV infected materials. Greater understanding of the transmission of BSV will contributed immensely to the development of control strategies for banana streak disease.
