The banana streak viruses (BSVs) are some of the most difficult of the viral pathogens of banana to detect. The presence of endogenous badnaviral DNA in the banana genome has the potential to cause false positive results in PCR unless appropriate precautions are taken. Antibody-based detection assays, which target markers of viral infection such as virions or viral proteins, provide a solution to the problem of discriminating endogenous from exogenous viral DNA. However, the development of serological assays for BSV, such as immunocapture PCR, is constrained by a worldwide shortage of BSV antibodies. It is not an easy task to prepare new BSV antibodies, as it is a technically difficult task to purify the BSVs to adequate purity to be used as immunogens, and the BSV capsid protein is poorly characterised, thus limiting in vitro protein expression strategies.The BSV capsid protein is cleaved from a large polyprotein through the action of the virus-encoded aspartic protease (AP) enzyme, but the enzyme substrate sites, and hence the protein boundaries, have not yet been determined. In this study, we investigated the expression and purification of the aspartic protease (AP) using the model caulimovirid, cauliflower mosaic virus (CaMV). This experimental system was chosen in preference to using one of the BSVs, as CaMV is a very well characterised virus and is easy to propagate and manipulate in the glasshouse and laboratory. Epitope mapping experiments for Banana streak Mysore virus (BSMYV) by a previous student in this laboratory determined that the immunodominant linear epitopes were located in a short, intrinsically disordered protein region at the very N-terminus (NID) of the capsid protein. The CaMV AP and NID domain protein were successfully expressed in E. coli using methods developed for mammalian cell-infecting retroviruses, but the AP was partitioned into inclusion bodies and formed part of the insoluble fraction of total proteins that were isolated. This AP was partially solubilised but was catalytically inactive when exposed to a NID substrate protein. This failure is likely a consequence of improper folding of the AP. A eukaryotic protein expression system based on the yeast Pichia pastoris, was trialled but there was no observable expression of CaMV AP in all clones tested. This line of research was thus terminated due to the time limitations of the project, and experiments with BSV never began.From the previous research, by using chemically synthesised peptides that mimic the epitopes in the NID domain, several antisera have been raised in rabbits for BSMYV, however, these antisera have never been evaluated. In this project, a novel method to produce antibodies against some common BSV species was conducted using the Multiple antigenic peptide-8 (MAP-8) display system, which is a dendritic structure of peptides on a lysine scaffold with no traditional carrier protein. Screening and evaluation of four different types of BSMYV antibodies including whole-virus antibody JVQ1, peptide antibody E1-KLH with Keyhole limpet hemocyanin (KLH) carrier protein, peptide antibody E-BSA with Bovine serum albumin (BSA) carrier protein, and peptide antibody MY-MAP8 with MAP8 dendrimer structure were done. The new anti-peptide antibodies produced using the MY-MAP8 system showed high specificity and sensitivity via ISEM, ELISA, IC PCR, and Western Blot. This technology was extended to produce antibodies against four more BSV species and shows great promise for generating immunodiagnostic reagents for a broad range of the Caulimoviridae.The badnavirus replication cycle is poorly understood and most knowledge is based on extrapolations from model viruses such as CaMV. However, in contrast to CaMV, badnaviruses are thought not to produce viroplasms and therefore it has been a mystery as to where in the cell cytoplasm that reverse transcription and virion assembly occurs. In this study, ultrathin sections of a banana leaf infected with banana streak MY virus were examined by transmission electron microscopy. Electron-dense inclusion bodies (EDIBs) were sporadically distributed in parenchymatous tissues of the leaf, most commonly in the palisade and spongy mesophyll cells. These EDIBs had a characteristic structure, comprising an electron-dense core, a single, encircling lacuna and an outer ring of electron-dense material. However, much less frequently, EDIBs with two or three lacunae were observed. In the outer ring, densely packed virions were visible with a shape and size consistent with that expected for badnaviruses. Immunogold labelling was done with primary antibodies that detected the N-terminus of the capsid protein and strong labelling of the outer ring but not the central core or lacuna was observed. It is concluded that the EDIBs that were observed are equivalent in function to the viroplasms of CaMV, although obviously different in composition as there is not a paralogue of the transactivation/viroplasm protein in the badnavirus genome. It is postulated that production of a viroplasm could be a conserved characteristic of all members of the Caulimoviridae.