Abstract. Pineapple mealybug wilt-associated virus 1 (PMWaV-1), 2 (PMWaV-2) and 3 (PMWaV-3) have been detected in Australian commercial pineapple crops, along with a previously undescribed ampelovirus, for which the name Pineapple mealybug wilt-associated virus 5 (PMWaV-5) is proposed. Partial sequences extending from open reading frame 1b through to the heat shock protein homologue were obtained for PMWaV-1, -3 and -5. Phylogenetic analyses of selected regions of these sequences indicated that PMWaV-5 is a distinct species and most closely related to PMWaV-1. The amino acid sequence variation observed in the RNA-dependent RNA polymerase region of PMWaV-1 isolates was 95.8-98.4% and of PMWaV-3 isolates was 92.2-99.5%.In surveys of mealybug wilt disease (MWD) affected crops, none of the four viruses was clearly associated with the disease at all survey sites. A statistically significant association (P < 0.001) between the presence of PMWaV-2 and symptoms was observed at one survey site (site 3), but the virus was at a low incidence at the remaining three survey sites. By contrast, although PMWaV-1 and -3 were equally distributed between symptomless and MWD-affected plants at site 3, there was a statistically significant (P < 0.001) association between each of these two viruses and MWD at sites 1 and 4. At site 2, there was a statistically significant (P < 0.001) association only between PMWaV-3 and MWD. PMWaV-1 was the most commonly found of the four viruses and conversely PMWaV-5 was only occasionally found. Australian isolates of PMWaV-1, -2 and -3 were transmitted by the mealybug species Dysmicoccus brevipes.

Using biochemical, serological, and cytopathological evidence, we have confirmed that banana bract mosaic virus (BBrMV) is a distinct member of the family Potyviridae. Virions of a Philippine isolate of BBrMV were purified from field-infected banana cv. Cardaba. Particles were approximately 725-nm long, banded at a density equivalent to 1.29 to 1.31 g/ml in cesium chloride equilibrium gradients, and had an A(260/280) of 1.17. Yields of about 4 mg/kg were obtained from fresh or frozen leaf midrib or lamina tissue. Three major protein species with sizes of 31, 37, and 39 kDa were resolved from dissociated virions, and all reacted specifically with polyclonal antibodies to BBrMV. Infected leaf cells contained typical pinwheel inclusions. Virus-specific cDNA was amplified from field samples by reverse transcription-polymerase chain reaction (RT-PCR) assay using potyvirus degenerate primers. In plate-trapped antigen-enzyme-linked immunosorbent assay (ELISA), weak serological relationships were demonstrated between BBrMV and other members of the family Potyviridae, including abaca mosaic (AbaMV), dasheen mosaic, maize dwarf mosaic, sorghum mosaic, sugarcane mosaic, and wheat streak mosaic viruses. Despite similarities in the symptoms caused by the two viruses, AbaMV was serologically distinct from BBrMV and reacted only weakly, or not at all, with BBrMV antibodies in double-antibody sandwich (DAS)-ELISA. No cross reactions were observed when RT-PCR products from the two viruses were examined by Southern blot hybridization using BBrMV- and AbaMV-specific digoxigenin-labeled DNA probes. BBrMV was consistently associated with banana bract mosaic disease, as assessed by DAS-ELISA and Southern blot hybridization using DNA probes. The known geographical distribution of BBrMV was extended to include India (Kokkan disease) and Sri Lanka.

Banana mild mosaic virus (BanMMV) is a previously undescribed filamentous virus infecting Musa spp. The complete genome has been sequenced from PCR clones and consists of 7352 nucleotides, encoding five open reading frames (ORFs) of 205, 25.5, 12.4, 8.0 and 26.8 kDa, respectively. BanMMV was most closely related to fovea- and carlaviruses, based on phylogenetic analysis using a portion of the viral replicase. Analysis of other parts of the genome revealed similarities with fovea-, carla- and potexviruses, but the virus was not clearly aligned to any previously recognised genus.

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